tinyUSB/test/vendor/ceedling/docs/CeedlingPacket.md

[All code is copyright © 2010-2012 Ceedling Project
by Mike Karlesky, Mark VanderVoord, and Greg Williams.

This Documentation Is Released Under a
Creative Commons 3.0 Attribution Share-Alike License]

What the What?

Assembling build environments for C projects - especially with
automated unit tests - is a pain. Whether it's Make or Rake or Premake
or what-have-you, set up with an all-purpose build environment
tool is tedious and requires considerable glue code to pull together
the necessary tools and libraries. Ceedling allows you to generate
an entire test and build environment for a C project from a single
YAML configuration file. Ceedling is written in Ruby and works
with the Rake build tool plus other goodness like Unity and CMock
- the unit testing and mocking frameworks for C. Ceedling and
its complementary tools can support the tiniest of embedded
processors, the beefiest 64 bit power houses available, and
everything in between.

For a build project including unit tests and using the default
toolchain gcc, the configuration file could be as simple as this:

```yaml
:project:
  :build_root: project/build/
  :release_build: TRUE

:paths:
  :test:
    - tests/**
  :source:
    - source/**
```

From the command line, to build the release version of your project,
you would simply run `ceedling release`. To run all your unit tests,
you would run `ceedling test:all`. That's it!

Of course, many more advanced options allow you to configure
your project with a variety of features to meet a variety of needs.
Ceedling can work with practically any command line toolchain
and directory structure – all by way of the configuration file.
Further, because Ceedling piggy backs on Rake, you can add your
own Rake tasks to accomplish project tasks outside of testing
and release builds. A facility for plugins also allows you to
extend Ceedling's capabilities for needs such as custom code
metrics reporting and coverage testing.

What's with this Name?

Glad you asked. Ceedling is tailored for unit tested C projects
and is built upon / around Rake (Rake is a Make replacement implemented
in the Ruby scripting language). So, we've got C, our Rake, and
the fertile soil of a build environment in which to grow and tend
your project and its unit tests. Ta da - _Ceedling_.

What Do You Mean "tailored for unit tested C projects"?

Well, we like to write unit tests for our C code to make it lean and
mean (that whole [Test-Driven Development][tdd]
thing). Along the way, this style of writing C code spawned two
tools to make the job easier: a unit test framework for C called
_Unity_ and a mocking library called _CMock_. And, though it's
not directly related to testing, a C framework for exception
handling called _CException_ also came along.

[tdd]: http://en.wikipedia.org/wiki/Test-driven_development

These tools and frameworks are great, but they require quite
a bit of environment support to pull them all together in a convenient,
usable fashion. We started off with Rakefiles to assemble everything.
These ended up being quite complicated and had to be hand-edited
or created anew for each new project. Ceedling replaces all that
tedium and rework with a configuration file that ties everything
together.

Though Ceedling is tailored for unit testing, it can also go right ahead
and build your final binary release artifact for you as well. Or,
Ceedling and your tests can live alongside your existing release build
setup. That said, Ceedling is more powerful as a unit test build
environment than it is a general purpose release build environment;
complicated projects including separate bootloaders or multiple library
builds, etc. are not its strong suit.

Hold on. Back up. Ruby? Rake? YAML? Unity? CMock? CException?

Seem overwhelming? It's not bad at all, and for the benefits tests
bring us, it's all worth it.

[Ruby][] is a handy scripting
language like Perl or Python. It's a modern, full featured language
that happens to be quite handy for accomplishing tasks like code
generation or automating one's workflow while developing in
a compiled language such as C.

[Ruby]: http://www.ruby-lang.org/en/

[Rake][] is a utility written in Ruby
for accomplishing dependency tracking and task automation
common to building software. It's a modern, more flexible replacement
for [Make][]).
Rakefiles are Ruby files, but they contain build targets similar
in nature to that of Makefiles (but you can also run Ruby code in
your Rakefile).

[Rake]: http://rubyrake.org/
[Make]: http://en.wikipedia.org/wiki/Make_(software)

[YAML][] is a "human friendly data serialization standard for all
programming languages." It's kinda like a markup language, but don't
call it that. With a YAML library, you can [serialize][] data structures
to and from the file system in a textual, human readable form. Ceedling
uses a serialized data structure as its configuration input.

[YAML]: http://en.wikipedia.org/wiki/Yaml
[serialize]: http://en.wikipedia.org/wiki/Serialization

[Unity] is a [unit test framework][test] for C. It provides facilities
for test assertions, executing tests, and collecting / reporting test
results. Unity derives its name from its implementation in a single C
source file (plus two C header files) and from the nature of its
implementation - Unity will build in any C toolchain and is configurable
for even the very minimalist of processors.

[Unity]: http://github.com/ThrowTheSwitch/Unity
[test]: http://en.wikipedia.org/wiki/Unit_testing

[CMock] is a tool written in Ruby able to generate entire
[mock functions][mock] in C code from a given C header file. Mock
functions are invaluable in [interaction-based unit testing][ut].
CMock's generated C code uses Unity.

[CMock]: http://github.com/ThrowTheSwitch/CMock
[mock]: http://en.wikipedia.org/wiki/Mock_object
[ut]: http://martinfowler.com/articles/mocksArentStubs.html

[CException] is a C source and header file that provide a simple
[exception mechanism][exn] for C by way of wrapping up the
[setjmp / longjmp][setjmp] standard library calls. Exceptions are a much
cleaner and preferable alternative to managing and passing error codes
up your return call trace.

[CException]: http://github.com/ThrowTheSwitch/CException
[exn]: http://en.wikipedia.org/wiki/Exception_handling
[setjmp]: http://en.wikipedia.org/wiki/Setjmp.h

Notes
-----

* YAML support is included with Ruby - requires no special installation
  or configuration.

* Unity, CMock, and CException are bundled with Ceedling, and
  Ceedling is designed to glue them all together for your project
  as seamlessly as possible.


Installation & Setup: What Exactly Do I Need to Get Started?
------------------------------------------------------------

As a [Ruby gem](http://docs.rubygems.org/read/chapter/1):

1. [Download and install Ruby](http://www.ruby-lang.org/en/downloads/)

2. Use Ruby's command line gem package manager to install Ceedling:
   `gem install ceedling`
   (Unity, CMock, and CException come along with Ceedling for free)

3. Execute Ceedling at command line to create example project
   or an empty Ceedling project in your filesystem (executing
   `ceedling help` first is, well, helpful).

Gem install notes:

1. Steps 1-2 are a one time affair for your local environment.
   When steps 1-2 are completed once, only step 3 is needed for
   each new project.



General notes:

1. Certain advanced features of Ceedling rely on gcc and cpp
   as preprocessing tools. In most *nix systems, these tools
   are already available. For Windows environments, we recommend
   the [mingw project](http://www.mingw.org/) (Minimalist
   GNU for Windows). This represents an optional, additional
   setup / installation step to complement the list above. Upon
   installing mingw ensure your system path is updated or set
   [:environment][:path] in your `project.yml` file (see
   environment section later in this document).

2. To use a project file name other than the default `project.yml`
   or place the project file in a directory other than the one
   in which you'll run Rake, create an environment variable
   `CEEDLING_MAIN_PROJECT_FILE` with your desired project
   file path.

3. To better understand Rake conventions, Rake execution,
   and Rakefiles, consult the [Rake tutorial, examples, and
   user guide](http://rubyrake.org/).

4. When using Ceedling in Windows environments, a test file name may 
   not include the sequences “patch” or “setup”. The Windows Installer 
   Detection Technology (part of UAC), requires administrator 
   privileges to execute file names with these strings.



Now What? How Do I Make It GO?
------------------------------

We're getting a little ahead of ourselves here, but it's good
context on how to drive this bus. Everything is done via the command
line. We'll cover conventions and how to actually configure
your project in later sections.

To run tests, build your release artifact, etc., you will be interacting
with Rake on the command line. Ceedling works with Rake to present
you with named tasks that coordinate the file generation and
build steps needed to accomplish something useful. You can also
add your own independent Rake tasks or create plugins to extend
Ceedling (more on this later).


* `ceedling [no arguments]`:

  Run the default Rake task (conveniently recognized by the name default
  by Rake). Neither Rake nor Ceedling provide a default task. Rake will
  abort if run without arguments when no default task is defined. You can
  conveniently define a default task in the Rakefile discussed in the
  preceding setup & installation section of this document.

* `ceedling -T`:

  List all available Rake tasks with descriptions (Rake tasks without
  descriptions are not listed). -T is a command line switch for Rake and
  not the same as tasks that follow.

* `ceedling <tasks...> --trace`:

  For advanced users troubleshooting a confusing build error, debug
  Ceedling or a plugin, --trace provides a stack trace of dependencies
  walked during task execution and any Ruby failures along the way. Note
  that --trace is a command line switch for Rake and is not the same as
  tasks that follow.

* `ceedling environment`:

  List all configured environment variable names and string values. This
  task is helpful in verifying the evaluatio of any Ruby expressions in
  the [:environment] section of your config file.`: Note: Ceedling may
  set some convenience environment variables by default.

* `ceedling paths:*`:

  List all paths collected from [:paths] entries in your YAML config
  file where * is the name of any section contained in [:paths]. This
  task is helpful in verifying the expansion of path wildcards / globs
  specified in the [:paths] section of your config file.

* `ceedling files:assembly`
* `ceedling files:header`
* `ceedling files:source`
* `ceedling files:test`

  List all files and file counts collected from the relevant search
  paths specified by the [:paths] entries of your YAML config file. The
  files:assembly task will only be available if assembly support is
  enabled in the [:release_build] section of your configuration file.

* `ceedling options:*`:

  Load and merge configuration settings into the main project
  configuration. Each task is named after a *.yml file found in the
  configured options directory. See documentation for the configuration
  setting [:project][:options_path] and for options files in advanced
  topics.

* `ceedling test:all`:

  Run all unit tests (rebuilding anything that's changed along the way).

* `ceedling test:delta`:

  Run only those unit tests for which the source or test files have
  changed (i.e. incremental build). Note: with the
  [:project][:use_test_preprocessor] configuration file option set,
  runner files are always regenerated limiting the total efficiency this
  text execution option can afford.

* `ceedling test:*`:

  Execute the named test file or the named source file that has an
  accompanying test. No path. Examples: ceedling test:foo.c or ceed
  test:test_foo.c

* `ceedling test:pattern[*]`:

  Execute any tests whose name and/or path match the regular expression
  pattern (case sensitive). Example: ceedling "test:pattern[(I|i)nit]" will
  execute all tests named for initialization testing. Note: quotes may
  be necessary around the ceedling parameter to distinguish regex characters
  from command line operators.

* `ceedling test:path[*]`:

  Execute any tests whose path contains the given string (case
  sensitive). Example: ceedling test:path[foo/bar] will execute all tests
  whose path contains foo/bar. Note: both directory separator characters
  / and \ are valid.

* `ceedling release`:

  Build all source into a release artifact (if the release build option
  is configured).

* `ceedling release:compile:*`:

  Sometimes you just need to compile a single file dagnabit. Example:
  ceedling release:compile:foo.c

* `ceedling release:assemble:*`:

  Sometimes you just need to assemble a single file doggonit. Example:
  ceedling release:assemble:foo.s

* `ceedling module:create[Filename]`:
* `ceedling module:create[<Path:>Filename]`:

  It's often helpful to create a file automatically. What's better than
  that? Creating a source file, a header file, and a corresponding test
  file all in one step!

  There are also patterns which can be specified to automatically generate
  a bunch of files. Try `ceedling module:create[Poodles,mch]` for example!

  The module generator has several options you can configure.
  F.e. Generating the source/header/test file in a subdirectory (by adding <Path> when calling module:create).
  For more info, refer to the [Module Generator](https://github.com/ThrowTheSwitch/Ceedling/blob/master/docs/CeedlingPacket.md#module-generator) section.

* `ceedling logging <tasks...>`:

  Enable logging to <build path>/logs. Must come before test and release
  tasks to log their steps and output. Log names are a concatenation of
  project, user, and option files loaded. User and option files are
  documented in the advanced topics section of this document.

* `ceedling verbosity[x] <tasks...>`:

  Change the default verbosity level. [x] ranges from 0 (quiet) to 4
  (obnoxious). Level [3] is the default. The verbosity task must precede
  all tasks in the command line list for which output is desired to be
  seen. Verbosity settings are generally most meaningful in conjunction
  with test and release tasks.

* `ceedling summary`:

  If plugins are enabled, this task will execute the summary method of
  any plugins supporting it. This task is intended to provide a quick
  roundup of build artifact metrics without re-running any part of the
  build.

* `ceedling clean`:

  Deletes all toolchain binary artifacts (object files, executables),
  test results, and any temporary files. Clean produces no output at the
  command line unless verbosity has been set to an appreciable level.

* `ceedling clobber`:

  Extends clean task's behavior to also remove generated files: test
  runners, mocks, preprocessor output. Clobber produces no output at the
  command line unless verbosity has been set to an appreciable level.

To better understand Rake conventions, Rake execution, and
Rakefiles, consult the [Rake tutorial, examples, and user guide][guide].

[guide]: http://rubyrake.org/

At present, none of Ceedling's commands provide persistence.
That is, they must each be specified at the command line each time
they are needed. For instance, Ceedling's verbosity command
only affects output at the time it's run.

Individual test and release file tasks
are not listed in `-T` output. Because so many files may be present
it's unwieldy to list them all.

Multiple rake tasks can be executed at the command line (order
is executed as provided). For example, `ceed
clobber test:all release` will removed all generated files;
build and run all tests; and then build all source - in that order.
If any Rake task fails along the way, execution halts before the
next task.

The `clobber` task removes certain build directories in the
course of deleting generated files. In general, it's best not
to add to source control any Ceedling generated directories
below the root of your top-level build directory. That is, leave
anything Ceedling & its accompanying tools generate out of source
control (but go ahead and add the top-level build directory that
holds all that stuff). Also, since Ceedling is pretty smart about
what it rebuilds and regenerates, you needn't clobber often.

Important Conventions
=====================

Directory Structure, Filenames & Extensions
-------------------------------------------

Much of Ceedling's functionality is driven by collecting files
matching certain patterns inside the paths it's configured
to search. See the documentation for the [:extensions] section
of your configuration file (found later in this document) to
configure the file extensions Ceedling uses to match and collect
files. Test file naming is covered later in this section.

Test files and source files must be segregated by directories.
Any directory structure will do. Tests can be held in subdirectories
within source directories, or tests and source directories
can be wholly separated at the top of your project's directory
tree.

Search Path Order
-----------------

When Ceedling searches for files (e.g. looking for header files
to mock) or when it provides search paths to any of the default
gcc toolchain executables, it organizes / prioritizes its search
paths. The order is always: test paths, support paths, source
paths, and then include paths. This can be useful, for instance,
in certain testing scenarios where we desire Ceedling or a compiler
to find a stand-in header file in our support directory before
the actual source header file of the same name.

This convention only holds when Ceedling is using its default
tool configurations and / or when tests are involved. If you define
your own tools in the configuration file (see the [:tools] section
documented later in this here document), you have complete control
over what directories are searched and in what order. Further,
test and support directories are only searched when appropriate.
That is, when running a release build, test and support directories
are not used at all.

Source Files & Binary Release Artifacts
---------------------------------------

Your binary release artifact results from the compilation and
linking of all source files Ceedling finds in the specified source
directories. At present only source files with a single (configurable)
extension are recognized. That is, *.c and *.cc files will not
both be recognized - only one or the other. See the configuration
options and defaults in the documentation for the [:extensions]
sections of your configuration file (found later in this document).

Test Files & Executable Test Fixtures
-------------------------------------

Ceedling builds each individual test file with its accompanying
source file(s) into a single, monolithic test fixture executable.
Test files are recognized by a naming convention: a (configurable)
prefix such as "`test_`" in the file name with the same file extension
as used by your C source files. See the configuration options
and defaults in the documentation for the [:project] and [:extensions]
sections of your configuration file (found later in this document).
Depending on your configuration options, Ceedling can recognize
a variety of test file naming patterns in your test search paths.
For example: `test_some_super_functionality.c`, `TestYourSourceFile.cc`,
or `testing_MyAwesomeCode.C` could each be valid test file
names. Note, however, that Ceedling can recognize only one test
file naming convention per project.

Ceedling knows what files to compile and link into each individual
test executable by way of the #include list contained in each
test file. Any C source files in the configured search directories
that correspond to the header files included in a test file will
be compiled and linked into the resulting test fixture executable.
From this same #include list, Ceedling knows which files to mock
and compile and link into the test executable (if you use mocks
in your tests). That was a lot of clauses and information in a very
few sentences; the example that follows in a bit will make it clearer.

By naming your test functions according to convention, Ceedling
will extract and collect into a runner C file calls to all your
test case functions. This runner file handles all the execution
minutiae so that your test file can be quite simple and so that
you never forget to wire up a test function to be executed. In this
generated runner lives the `main()` entry point for the resulting
test executable. There are no configuration options for the
naming convention of your test case functions. A test case function
signature must have these three elements: void return, void
parameter list, and the function name prepended with lowercase
"`test`". In other words, a test function signature should look
like this: `void test``[any name you like]``(void)`.

A commented sample test file follows on the next page. Also, see
the sample project contained in the Ceedling documentation
bundle.

```c
// test_foo.c -----------------------------------------------
#include "unity.h"     // compile/link in Unity test framework
#include "types.h"     // header file with no *.c file -- no compilation/linking
#include "foo.h"       // source file foo.c under test
#include "mock_bar.h"  // bar.h will be found and mocked as mock_bar.c + compiled/linked in;
                       // foo.c includes bar.h and uses functions declared in it
#include "mock_baz.h"  // baz.h will be found and mocked as mock_baz.c + compiled/linked in
                       // foo.c includes baz.h and uses functions declared in it


void setUp(void) {}    // every test file requires this function;
                       // setUp() is called by the generated runner before each test case function

void tearDown(void) {} // every test file requires this function;
                       // tearDown() is called by the generated runner before each test case function

// a test case function
void test_Foo_Function1_should_Call_Bar_AndGrill(void)
{
    Bar_AndGrill_Expect();                    // setup function from mock_bar.c that instructs our
                                              // framework to expect Bar_AndGrill() to be called once
    TEST_ASSERT_EQUAL(0xFF, Foo_Function1()); // assertion provided by Unity
                                              // Foo_Function1() calls Bar_AndGrill() & returns a byte
}

// another test case function
void test_Foo_Function2_should_Call_Baz_Tec(void)
{
    Baz_Tec_ExpectAnd_Return(1);       // setup function provided by mock_baz.c that instructs our
                                       // framework to expect Baz_Tec() to be called once and return 1
    TEST_ASSERT_TRUE(Foo_Function2()); // assertion provided by Unity
}

// end of test_foo.c ----------------------------------------
```

From the test file specified above Ceedling will generate `test_foo_runner.c`;
this runner file will contain `main()` and call both of the example
test case functions.

The final test executable will be `test_foo.exe` (for Windows
machines or `test_foo.out` for *nix systems - depending on default
or configured file extensions). Based on the #include list above,
the test executable will be the output of the linker having processed
`unity.o`, `foo.o`, `mock_bar.o`, `mock_baz.o`, `test_foo.o`,
and `test_foo_runner.o`. Ceedling finds the files, generates
mocks, generates a runner, compiles all the files, and links
everything into the test executable. Ceedling will then run
the test executable and collect test results from it to be reported
to the developer at the command line.

For more on the assertions and mocks shown, consult the documentation
for Unity and CMock.

The Magic of Dependency Tracking
--------------------------------

Ceedling is pretty smart in using Rake to build up your project's
dependencies. This means that Ceedling automagically rebuilds
all the appropriate files in your project when necessary: when
your configuration changes, Ceedling or any of the other tools
are updated, or your source or test files change. For instance,
if you modify a header file that is mocked, Ceedling will ensure
that the mock is regenerated and all tests that use that mock are
rebuilt and re-run when you initiate a relevant testing task.
When you see things rebuilding, it's for a good reason. Ceedling
attempts to regenerate and rebuild only what's needed for a given
execution of a task. In the case of large projects, assembling
dependencies and acting upon them can cause some delay in executing
tasks.

With one exception, the trigger to rebuild or regenerate a file
is always a disparity in timestamps between a target file and
its source - if an input file is newer than its target dependency,
the target is rebuilt or regenerated. For example, if the C source
file from which an object file is compiled is newer than that object
file on disk, recompilation will occur (of course, if no object
file exists on disk, compilation will always occur). The one
exception to this dependency behavior is specific to your input
configuration. Only if your logical configuration changes
will a system-wide rebuild occur. Reorganizing your input configuration
or otherwise updating its file timestamp without modifying
the values within the file will not trigger a rebuild. This behavior
handles the various ways in which your input configuration can
change (discussed later in this document) without having changed
your actual project YAML file.

Ceedling needs a bit of help to accomplish its magic with deep
dependencies. Shallow dependencies are straightforward:
a mock is dependent on the header file from which it's generated,
a test file is dependent upon the source files it includes (see
the preceding conventions section), etc. Ceedling handles
these "out of the box." Deep dependencies are specifically a
C-related phenomenon and occur as a consequence of include statements
within C source files. Say a source file includes a header file
and that header file in turn includes another header file which
includes still another header file. A change to the deepest header
file should trigger a recompilation of the source file, a relinking
of all the object files comprising a test fixture, and a new execution
of that test fixture.

Ceedling can handle deep dependencies but only with the help
of a C preprocessor. Ceedling is quite capable, but a full C preprocessor
it ain't. Your project can be configured to use a C preprocessor
or not. Simple projects or large projects constructed so as to
be quite flat in their include structure generally don't need
deep dependency preprocessing - and can enjoy the benefits of
faster execution. Legacy code, on the other hand, will almost
always want to be tested with deep preprocessing enabled. Set
up of the C preprocessor is covered in the documentation for the
[:project] and [:tools] section of the configuration file (later
in this document). Ceedling contains all the configuration
necessary to use the gcc preprocessor by default. That is, as
long as gcc is in your system search path, deep preprocessing
of deep dependencies is available to you by simply enabling it
in your project configuration file.

Ceedling's Build Output
-----------------------

Ceedling requires a top-level build directory for all the stuff
that it, the accompanying test tools, and your toolchain generate.
That build directory's location is configured in the [:project]
section of your configuration file (discussed later). There
can be a ton of generated files. By and large, you can live a full
and meaningful life knowing absolutely nothing at all about
the files and directories generated below the root build directory.

As noted already, it's good practice to add your top-level build
directory to source control but nothing generated beneath it.
You'll spare yourself headache if you let Ceedling delete and
regenerate files and directories in a non-versioned corner
of your project's filesystem beneath the top-level build directory.

The `artifacts` directory is the one and only directory you may
want to know about beneath the top-level build directory. The
subdirectories beneath `artifacts` will hold your binary release
target output (if your project is configured for release builds)
and will serve as the conventional location for plugin output.
This directory structure was chosen specifically because it
tends to work nicely with Continuous Integration setups that
recognize and list build artifacts for retrieval / download.

The Almighty Project Configuration File (in Glorious YAML)
----------------------------------------------------------

Please consult YAML documentation for the finer points of format
and to understand details of our YAML-based configuration file.
We recommend [Wikipedia's entry on YAML](http://en.wikipedia.org/wiki/Yaml)
for this. A few highlights from that reference page:

* YAML streams are encoded using the set of printable Unicode
  characters, either in UTF-8 or UTF-16

* Whitespace indentation is used to denote structure; however
  tab characters are never allowed as indentation

* Comments begin with the number sign ( # ), can start anywhere
  on a line, and continue until the end of the line unless enclosed
  by quotes

* List members are denoted by a leading hyphen ( - ) with one member
  per line, or enclosed in square brackets ( [ ] ) and separated
  by comma space ( , )

* Hashes are represented using the colon space ( : ) in the form
  key: value, either one per line or enclosed in curly braces
  ( { } ) and separated by comma space ( , )

* Strings (scalars) are ordinarily unquoted, but may be enclosed
  in double-quotes ( " ), or single-quotes ( ' )

* YAML requires that colons and commas used as list separators
  be followed by a space so that scalar values containing embedded
  punctuation can generally be represented without needing
  to be enclosed in quotes

* Repeated nodes are initially denoted by an ampersand ( & ) and
  thereafter referenced with an asterisk ( * )


Notes on what follows:

* Each of the following sections represent top-level entries
  in the YAML configuration file.

* Unless explicitly specified in the configuration file, default
  values are used by Ceedling.

* These three settings, at minimum, must be specified:
  * [:project][:build_root]
  * [:paths][:source]
  * [:paths][:test]

* As much as is possible, Ceedling validates your settings in
  properly formed YAML.

* Improperly formed YAML will cause a Ruby error when the YAML
  is parsed. This is usually accompanied by a complaint with
  line and column number pointing into the project file.

* Certain advanced features rely on gcc and cpp as preprocessing
  tools. In most *nix systems, these tools are already available.
  For Windows environments, we recommend the [mingw project](http://www.mingw.org/)
  (Minimalist GNU for Windows).

* Ceedling is primarily meant as a build tool to support automated
  unit testing. All the heavy lifting is involved there. Creating
  a simple binary release build artifact is quite trivial in
  comparison. Consequently, most default options and the construction
  of Ceedling itself is skewed towards supporting testing though
  Ceedling can, of course, build your binary release artifact
  as well. Note that complex binary release artifacts (e.g.
  application + bootloader or multiple libraries) are beyond
  Ceedling's release build ability.


Conventions / features of Ceedling-specific YAML:

* Any second tier setting keys anywhere in YAML whose names end
  in `_path` or `_paths` are automagically processed like all
  Ceedling-specific paths in the YAML to have consistent directory
  separators (i.e. "/") and to take advantage of inline Ruby
  string expansion (see [:environment] setting below for further
  explanation of string expansion).


**Let's Be Careful Out There:** Ceedling performs validation
on the values you set in your configuration file (this assumes
your YAML is correct and will not fail format parsing, of course).
That said, validation is limited to only those settings Ceedling
uses and those that can be reasonably validated. Ceedling does
not limit what can exist within your configuration file. In this
way, you can take full advantage of YAML as well as add sections
and values for use in your own custom plugins (documented later).
The consequence of this is simple but important. A misspelled
configuration section name or value name is unlikely to cause
Ceedling any trouble. Ceedling will happily process that section
or value and simply use the properly spelled default maintained
internally - thus leading to unexpected behavior without warning.

project: global project settings


* `build_root`:

  Top level directory into which generated path structure and files are
  placed. Note: this is one of the handful of configuration values that
  must be set. The specified path can be absolute or relative to your
  working directory.

  **Default**: (none)

* `use_exceptions`:

  Configures the build environment to make use of CException. Note that
  if you do not use exceptions, there's no harm in leaving this as its
  default value.

  **Default**: TRUE

* `use_mocks`:

  Configures the build environment to make use of CMock. Note that if
  you do not use mocks, there's no harm in leaving this setting as its
  default value.

  **Default**: TRUE

* `use_test_preprocessor`:

  This option allows Ceedling to work with test files that contain
  conditional compilation statements (e.g. #ifdef) and header files you
  wish to mock that contain conditional preprocessor statements and/or
  macros.

  Ceedling and CMock are advanced tools with sophisticated parsers.
  However, they do not include entire C language preprocessors.
  Consequently, with this option enabled, Ceedling will use gcc's
  preprocessing mode and the cpp preprocessor tool to strip down /
  expand test files and headers to their applicable content which can
  then be processed by Ceedling and CMock.

  With this option enabled, the gcc & cpp tools must exist in an
  accessible system search path and test runner files are always
  regenerated.

  **Default**: FALSE

* `use_deep_dependencies`:

  The base rules and tasks that Ceedling creates using Rake capture most
  of the dependencies within a standard project (e.g. when the source
  file accompanying a test file changes, the corresponding test fixture
  executable will be rebuilt when tests are re-run). However, deep
  dependencies cannot be captured this way. If a typedef or macro
  changes in a header file three levels of #include statements deep,
  this option allows the appropriate incremental build actions to occur
  for both test execution and release builds.

  This is accomplished by using the dependencies discovery mode of gcc.
  With this option enabled, gcc must exist in an accessible system
  search path.

  **Default**: FALSE

* `generate_deep_dependencies`:

  When `use_deep_dependencies` is set to TRUE, Ceedling will run a separate
  build step to generate the deep dependencies. If you are using gcc as your
  primary compiler, or another compiler that can generate makefile rules as
  a side effect of compilation, then you can set this to FALSE to avoid the
  extra build step but still use the deep dependencies data when deciding
  which source files to rebuild.

  **Default**: TRUE

* `test_file_prefix`:

  Ceedling collects test files by convention from within the test file
  search paths. The convention includes a unique name prefix and a file
  extension matching that of source files.

  Why not simply recognize all files in test directories as test files?
  By using the given convention, we have greater flexibility in what we
  do with C files in the test directories.

  **Default**: "test_"

* `options_paths`:

  Just as you may have various build configurations for your source
  codebase, you may need variations of your project configuration.

  By specifying options paths, Ceedling will search for other project
  YAML files, make command line tasks available (ceedling options:variation
  for a variation.yml file), and merge the project configuration of
  these option files in with the main project file at runtime. See
  advanced topics.

  Note these Rake tasks at the command line - like verbosity or logging
  control - must come before the test or release task they are meant to
  modify.

  **Default**: [] (empty)

* `release_build`:

  When enabled, a release Rake task is exposed. This configuration
  option requires a corresponding release compiler and linker to be
  defined (gcc is used as the default).

  More release configuration options are available in the release_build
  section.

  **Default**: FALSE


Example `[:project]` YAML blurb

```yaml
:project:
  :build_root: project_awesome/build
  :use_exceptions: FALSE
  :use_test_preprocessor: TRUE
  :use_deep_dependencies: TRUE
  :options_paths:
    - project/options
    - external/shared/options
  :release_build: TRUE
```

Ceedling is primarily concerned with facilitating the somewhat
complicated mechanics of automating unit tests. The same mechanisms
are easily capable of building a final release binary artifact
(i.e. non test code; the thing that is your final working software
that you execute on target hardware).


* `output`:

  The name of your release build binary artifact to be found in <build
  path>/artifacts/release. Ceedling sets the default artifact file
  extension to that as is explicitly specified in the [:extensions]
  section or as is system specific otherwise.

  **Default**: `project.exe` or `project.out`

* `use_assembly`:

  If assembly code is present in the source tree, this option causes
  Ceedling to create appropriate build directories and use an assembler
  tool (default is the GNU tool as - override available in the [:tools]
  section.

  **Default**: FALSE

* `artifacts`:

  By default, Ceedling copies to the <build path>/artifacts/release
  directory the output of the release linker and (optionally) a map
  file. Many toolchains produce other important output files as well.
  Adding a file path to this list will cause Ceedling to copy that file
  to the artifacts directory. The artifacts directory is helpful for
  organizing important build output files and provides a central place
  for tools such as Continuous Integration servers to point to build
  output. Selectively copying files prevents incidental build cruft from
  needlessly appearing in the artifacts directory. Note that inline Ruby
  string replacement is available in the artifacts paths (see discussion
  in the [:environment] section).

  **Default**: [] (empty)

Example `[:release_build]` YAML blurb

```yaml
:release_build:
  :output: top_secret.bin
  :use_assembly: TRUE
  :artifacts:
    - build/release/out/c/top_secret.s19
```

**paths**: options controlling search paths for source and header
(and assembly) files

* `test`:

  All C files containing unit test code. Note: this is one of the
  handful of configuration values that must be set.

  **Default**: [] (empty)

* `source`:

  All C files containing release code (code to be tested). Note: this is
  one of the handful of configuration values that must be set.

  **Default**: [] (empty)

* `support`:

  Any C files you might need to aid your unit testing. For example, on
  occasion, you may need to create a header file containing a subset of
  function signatures matching those elsewhere in your code (e.g. a
  subset of your OS functions, a portion of a library API, etc.). Why?
  To provide finer grained control over mock function substitution or
  limiting the size of the generated mocks.

  **Default**: [] (empty)

* `include`:

  Any header files not already in the source search path. Note there's
    no practical distinction between this search path and the source
    search path; it's merely to provide options or to support any
    peculiar source tree organization.

  **Default**: [] (empty)

* `test_toolchain_include`:

  System header files needed by the test toolchain - should your
  compiler be unable to find them, finds the wrong system include search
  path, or you need a creative solution to a tricky technical problem.
  Note that if you configure your own toolchain in the [:tools] section,
  this search path is largely meaningless to you. However, this is a
  convenient way to control the system include path should you rely on
  the default gcc tools.

  **Default**: [] (empty)

* `release_toolchain_include`:

  Same as preceding albeit related to the release toolchain.

  **Default**: [] (empty)

* `<custom>`

  Any paths you specify for custom list. List is available to tool
  configurations and/or plugins. Note a distinction. The preceding names
  are recognized internally to Ceedling and the path lists are used to
  build collections of files contained in those paths. A custom list is
  just that - a custom list of paths.

Notes on path grammar within the [:paths] section:

* Order of search paths listed in [:paths] is preserved when used by an
  entry in the [:tools] section

* Wherever multiple path lists are combined for use Ceedling prioritizes
  path groups as follows:
  test paths, support paths, source paths, include paths.

  This can be useful, for instance, in certain testing scenarios where
  we desire Ceedling or the compiler to find a stand-in header file before
  the actual source header file of the same name.

* Paths:

  1. can be absolute or relative

  2. can be singly explicit - a single fully specified path

  3. can include a glob operator (more on this below)

  4. can use inline Ruby string replacement (see [:environment]
     section for more)

  5. default as an addition to a specific search list (more on this
     in the examples)

  6. can act to subtract from a glob included in the path list (more
     on this in the examples)


[Globs](http://ruby.about.com/od/beginningruby/a/dir2.htm)
as used by Ceedling are wildcards for specifying directories
without the need to list each and every required search path.
Ceedling globs operate just as Ruby globs except that they are
limited to matching directories and not files. Glob operators
include the following * ** ? [-] {,} (note: this list is space separated
and not comma separated as commas are used within the bracket
operators).

* `*`:

  All subdirectories of depth 1 below the parent path and including the
  parent path

* `**`:

  All subdirectories recursively discovered below the parent path and
  including the parent path

* `?`:

  Single alphanumeric character wildcard

* `[x-y]`:

  Single alphanumeric character as found in the specified range

* `{x,y}`:

  Single alphanumeric character from the specified list

Example [:paths] YAML blurbs

```yaml
:paths:
  :source:              #together the following comprise all source search paths
    - project/source/*  #expansion yields all subdirectories of depth 1 plus parent directory
    - project/lib       #single path
  :test:                #all test search paths
    - project/**/test?  #expansion yields any subdirectory found anywhere in the project that
                        #begins with "test" and contains 5 characters

:paths:
  :source:                           #all source search paths
    - +:project/source/**            #all subdirectories recursively discovered plus parent directory
    - -:project/source/os/generated  #subtract os/generated directory from expansion of above glob
                                     #note that '+:' notation is merely aesthetic; default is to add

  :test:                             #all test search paths
    - project/test/bootloader        #explicit, single search paths (searched in the order specified)
    - project/test/application
    - project/test/utilities

  :custom:                           #custom path list
    - "#{PROJECT_ROOT}/other"        #inline Ruby string expansion
```

Globs and inline Ruby string expansion can require trial and
error to arrive at your intended results. Use the `ceedling paths:*`
command line options (documented in preceding section) to verify
your settings.

Ceedling relies on file collections automagically assembled
from paths, globs, and file extensions. File collections greatly
simplify project set up. However, sometimes you need to remove
from or add individual files to those collections.


* `test`:

  Modify the collection of unit test C files.

  **Default**: [] (empty)

* `source`:

  Modify the collection of all source files used in unit test builds and release builds.

  **Default**: [] (empty)

* `assembly`:

  Modify the (optional) collection of assembly files used in release builds.

  **Default**: [] (empty)

* `include`:

  Modify the collection of all source header files used in unit test builds (e.g. for mocking) and release builds.

  **Default**: [] (empty)

* `support`:

  Modify the collection of supporting C files available to unit tests builds.

  **Default**: [] (empty)


Note: All path grammar documented in [:paths] section applies
to [:files] path entries - albeit at the file path level and not
the directory level.

Example [:files] YAML blurb

```yaml
:files:
  :source:
    - callbacks/comm.c        # entry defaults to file addition
    - +:callbacks/comm*.c     # add all comm files matching glob pattern
    - -:source/board/atm134.c # not our board
  :test:
    - -:test/io/test_output_manager.c # remove unit tests from test build
```

**environment:** inserts environment variables into the shell
instance executing configured tools

Ceedling creates environment variables from any key / value
pairs in the environment section. Keys become an environment
variable name in uppercase. The values are strings assigned
to those environment variables. These value strings are either
simple string values in YAML or the concatenation of a YAML array.

Ceedling is able to execute inline Ruby string substitution
code to set environment variables. This evaluation occurs when
the project file is first processed for any environment pair's
value string including the Ruby string substitution pattern
`#{…}`. Note that environment value strings that _begin_ with
this pattern should always be enclosed in quotes. YAML defaults
to processing unquoted text as a string; quoting text is optional.
If an environment pair's value string begins with the Ruby string
substitution pattern, YAML will interpret the string as a Ruby
comment (because of the `#`). Enclosing each environment value
string in quotes is a safe practice.

[:environment] entries are processed in the configured order
(later entries can reference earlier entries).

Special case: PATH handling

In the specific case of specifying an environment key named _path_,
an array of string values will be concatenated with the appropriate
platform-specific path separation character (e.g. ':' on *nix,
';' on Windows). All other instances of environment keys assigned
YAML arrays use simple concatenation.

Example [:environment] YAML blurb

```yaml
:environment:
  - :license_server: gizmo.intranet        #LICENSE_SERVER set with value "gizmo.intranet"
  - :license: "#{`license.exe`}"           #LICENSE set to string generated from shelling out to
                                           #execute license.exe; note use of enclosing quotes

  - :path:                                 #concatenated with path separator (see special case above)
     - Tools/gizmo/bin                     #prepend existing PATH with gizmo path
     - "#{ENV['PATH']}"                    #pattern #{…} triggers ruby evaluation string substitution
                                           #note: value string must be quoted because of '#'

  - :logfile: system/logs/thingamabob.log  #LOGFILE set with path for a log file
```

**extension**: configure file name extensions used to collect lists of files searched in [:paths]

* `header`:

  C header files

  **Default**: .h

* `source`:

  C code files (whether source or test files)

  **Default**: .c

* `assembly`:

  Assembly files (contents wholly assembly instructions)

  **Default**: .s

* `object`:

  Resulting binary output of C code compiler (and assembler)

  **Default**: .o

* `executable`:

  Binary executable to be loaded and executed upon target hardware

  **Default**: .exe or .out (Win or *nix)

* `testpass`:

  Test results file (not likely to ever need a new value)

  **Default**: .pass

* `testfail`:

  Test results file (not likely to ever need a new value)

  **Default**: .fail

* `dependencies`:

  File containing make-style dependency rules created by gcc preprocessor

  **Default**: .d


Example [:extension] YAML blurb

    :extension:
      :source: .cc
      :executable: .bin

**defines**: command line defines used in test and release compilation by configured tools

* `test`:

  Defines needed for testing. Useful for:

  1. test files containing conditional compilation statements (i.e.
  tests active in only certain contexts)

  2. testing legacy source wherein the isolation of source under test
  afforded by Ceedling and its complementary tools leaves certain
  symbols unset when source files are compiled in isolation

  **Default**: [] (empty)

* `test_preprocess`:

  If [:project][:use_test_preprocessor] or
  [:project][:use_deep_dependencies] is set and code is structured in a
  certain way, the gcc preprocessor may need symbol definitions to
  properly preprocess files to extract function signatures for mocking
  and extract deep dependencies for incremental builds.

  **Default**: [] (empty)

* `release`:

  Defines needed for the release build binary artifact.

  **Default**: [] (empty)

* `release_preprocess`:

  If [:project][:use_deep_dependencies] is set and code is structured in
  a certain way, the gcc preprocessor may need symbol definitions to
  properly preprocess files for incremental release builds due to deep
  dependencies.

  **Default**: [] (empty)


Example [:defines] YAML blurb

```yaml
:defines:
  :test:
    - UNIT_TESTING  #for select cases in source to allow testing with a changed behavior or interface
    - OFF=0
    - ON=1
    - FEATURE_X=ON
  :source:
    - FEATURE_X=ON
```


**libraries**: command line defines used in test and release compilation by configured tools

Ceedling allows you to pull in specific libraries for the purpose of release and test builds.
It has a few levels of support for this. Start by adding a :libraries main section in your
configuration. In this section, you can optionally have the following subsections:

* `test`:

  Library files that should be injected into your tests when linking occurs.
  These can be specified as either relative or absolute paths. These files MUST
  exist when the test attempts to build.

* `source`:

  Library files that should be injected into your release when linking occurs. These
  can be specified as either relative or absolute paths. These files MUST exist when
  the release attempts to build UNLESS you are using the subprojects plugin. In that
  case, it will attempt to build that library for you as a dynamic dependency.

* `system`:

  These libraries are assumed to be in the tool path somewhere and shouldn't need to be
  specified. The libraries added here will be injected into releases and tests.

* `flag`:

  This is the method of adding an argument for each library. For example, gcc really likes
  it when you specify “-l${1}”

Notes:

* If you've specified your own link step, you are going to want to add ${4} to your argument
list in the place where library files should be added to the command call. For gcc, this is
often the very end. Other tools may vary.


**flags**: configure per-file compilation and linking flags

Ceedling tools (see later [:tools] section) are used to configure
compilation and linking of test and source files. These tool
configurations are a one-size-fits-all approach. Should individual files
require special compilation or linking flags, the settings in the
[:flags] section work in conjunction with tool definitions by way of
argument substitution to achieve this.

* `release`:

  [:compile] or [:link] flags for release build

* `test`:

  [:compile] or [:link] flags for test build

Notes:

* Ceedling works with the [:release] and [:test] build contexts
  as-is; plugins can add additional contexts

* Only [:compile] and [:link] are recognized operations beneath
  a context

* File specifiers do not include a path or file extension

* File specifiers are case sensitive (must match original file
  name)

* File specifiers do support regular expressions if encased in quotes

* '*' is a special (optional) file specifier to provide flags
  to all files not otherwise specified


Example [:flags] YAML blurb

```yaml
:flags:
  :release:
    :compile:
      :main:       # add '-Wall' to compilation of main.c
        - -Wall
      :fan:        # add '--O2' to compilation of fan.c
        - --O2
      :'test_.+':   # add '-pedantic' to all test-files
        - -pedantic
      :*:          # add '-foo' to compilation of all files not main.c or fan.c
        - -foo
  :test:
    :compile:
      :main:       # add '--O1' to compilation of main.c as part of test builds including main.c
        - --O1
    :link:
      :test_main:  # add '--bar --baz' to linking of test_main.exe
        - --bar
        - --baz
```

Ceedling sets values for a subset of CMock settings. All CMock
options are available to be set, but only those options set by
Ceedling in an automated fashion are documented below. See CMock
documentation.

**cmock**: configure CMock's code generation options and set symbols used to modify CMock's compiled features
Ceedling sets values for a subset of CMock settings. All CMock options are available to be set, but only those options set by Ceedling in an automated fashion are documented below. See CMock documentation.

* `enforce_strict_ordering`:

  Tests fail if expected call order is not same as source order

  **Default**: TRUE

* `mock_path`:

  Path for generated mocks

  **Default**: <build path>/tests/mocks

* `defines`:

  List of conditional compilation symbols used to configure CMock's
  compiled features. See CMock documentation to understand available
  options. No symbols must be set unless defaults are inappropriate for
  your specific environment. All symbols are used only by Ceedling to
  compile CMock C code; contents of [:defines] are ignored by CMock's
  Ruby code when instantiated.

  **Default**: [] (empty)

* `verbosity`:

  If not set, defaults to Ceedling's verbosity level

* `plugins`:

  If [:project][:use_exceptions] is enabled, the internal plugins list is pre-populated with 'cexception'.

  Whether or not you have included [:cmock][:plugins] in your
  configuration file, Ceedling automatically adds 'cexception' to the
  plugin list if exceptions are enabled. To add to the list Ceedling
  provides CMock, simply add [:cmock][:plugins] to your configuration
  and specify your desired additional plugins.

* `includes`:

  If [:cmock][:unity_helper] set, pre-populated with unity_helper file
  name (no path).

  The [:cmock][:includes] list works identically to the plugins list
  above with regard to adding additional files to be inserted within
  mocks as #include statements.


The last four settings above are directly tied to other Ceedling
settings; hence, why they are listed and explained here. The
first setting above, [:enforce_strict_ordering], defaults
to FALSE within CMock. It is set to TRUE by default in Ceedling
as our way of encouraging you to use strict ordering. It's a teeny
bit more expensive in terms of code generated, test execution
time, and complication in deciphering test failures. However,
it's good practice. And, of course, you can always disable it
by overriding the value in the Ceedling YAML configuration file.


**cexception**: configure symbols used to modify CException's compiled features

* `defines`:

  List of conditional compilation symbols used to configure CException's
  features in its source and header files. See CException documentation
  to understand available options. No symbols must be set unless the
  defaults are inappropriate for your specific environment.

  **Default**: [] (empty)


**unity**: configure symbols used to modify Unity's compiled features

* `defines`:

  List of conditional compilation symbols used to configure Unity's
  features in its source and header files. See Unity documentation to
  understand available options. No symbols must be set unless the
  defaults are inappropriate for your specific environment. Most Unity 
  defines can be easily configured through the YAML file.

  **Default**: [] (empty)

Example [:unity] YAML blurbs
```yaml
:unity: #itty bitty processor & toolchain with limited test execution options
  :defines:
    - UNITY_INT_WIDTH=16           #16 bit processor without support for 32 bit instructions
    - UNITY_EXCLUDE_FLOAT          #no floating point unit

:unity: #great big gorilla processor that grunts and scratches
  :defines:
    - UNITY_SUPPORT_64                    #big memory, big counters, big registers
    - UNITY_LINE_TYPE=\"unsigned int\"    #apparently we're using really long test files,
    - UNITY_COUNTER_TYPE=\"unsigned int\" #and we've got a ton of test cases in those test files
    - UNITY_FLOAT_TYPE=\"double\"         #you betcha
```


Notes on Unity configuration:

* **Verification** - Ceedling does no verification of your configuration
  values. In a properly configured setup, your Unity configuration
  values are processed, collected together with any test define symbols
  you specify elsewhere, and then passed to your toolchain during test
  compilation. Unity's conditional compilation statements, your
  toolchain's preprocessor, and/or your toolchain's compiler will
  complain appropriately if your specified configuration values are
  incorrect, incomplete, or incompatible.

* **Routing $stdout** - Unity defaults to using `putchar()` in C's
  standard library to display test results. For more exotic environments
  than a desktop with a terminal (e.g. running tests directly on a
  non-PC target), you have options. For example, you could create a
  routine that transmits a character via RS232 or USB. Once you have
  that routine, you can replace `putchar()` calls in Unity by overriding
  the function-like macro `UNITY_OUTPUT_CHAR`. Consult your toolchain
  and shell documentation. Eventhough this can also be defined in the YAML file
  most shell environments do not handle parentheses as command line arguments 
  very well. To still be able to add this functionality all necessary 
  options can be defined in the `unity_config.h`. Unity needs to be told to look for 
  the `unity_config.h` in the YAML file, though. 

Example [:unity] YAML blurbs
```yaml
:unity:
  :defines:
  	- UNITY_INCLUDE_CONFIG_H
```

Example unity_config.h
```
#ifndef UNITY_CONFIG_H
#define UNITY_CONFIG_H

#include "uart_output.h" //Helper library for your custom environment

#define UNITY_INT_WIDTH 16
#define UNITY_OUTPUT_START() uart_init(F_CPU, BAUD) //Helperfunction to init UART
#define UNITY_OUTPUT_CHAR(a) uart_putchar(a) //Helperfunction to forward char via UART
#define UNITY_OUTPUT_COMPLETE() uart_complete() //Helperfunction to inform that test has ended

#endif
```


**tools**: a means for representing command line tools for use under
Ceedling's automation framework

Ceedling requires a variety of tools to work its magic. By default,
the GNU toolchain (gcc, cpp, as) are configured and ready for
use with no additions to the project configuration YAML file.
However, as most work will require a project-specific toolchain,
Ceedling provides a generic means for specifying / overriding
tools.

* `test_compiler`:

  Compiler for test & source-under-test code
  ${1}: input source ${2}: output object ${3}: optional output list ${4}: optional output dependencies file

  **Default**: gcc

* `test_linker`:

  Linker to generate test fixture executables
  ${1}: input objects ${2}: output binary ${3}: optional output map ${4}: optional library list

  **Default**: gcc

* `test_fixture`:

  Executable test fixture
  ${1}: simulator as executable with ${1} as input binary file argument or native test executable

  **Default**: ${1}

* `test_includes_preprocessor`:

  Extractor of #include statements
  ${1}: input source file

  **Default**: cpp

* `test_file_preprocessor`:

  Preprocessor of test files (macros, conditional compilation statements)
  ${1}: input source file ${2}: preprocessed output source file

  **Default**: gcc

* `test_dependencies_generator`:

  Discovers deep dependencies of source & test (for incremental builds)
  ${1}: input source file ${2}: compiled object filepath ${3}: output dependencies file

  **Default**: gcc

* `release_compiler`:

  Compiler for release source code
  ${1}: input source ${2}: output object ${3}: optional output list ${4}: optional output dependencies file

  **Default**: gcc

* `release_assembler`:

  Assembler for release assembly code
  ${1}: input assembly source file ${2}: output object file

  **Default**: as

* `release_linker`:

  Linker for release source code
  ${1}: input objects ${2}: output binary ${3}: optional output map ${4}: optional library list

  **Default**: gcc

* `release_dependencies_generator`:

  Discovers deep dependencies of source files (for incremental builds)
  ${1}: input source file ${2}: compiled object filepath ${3}: output dependencies file

  **Default**: gcc


A Ceedling tool has a handful of configurable elements:

1. [:executable] (required) - Command line executable having
   the form of:

2. [:arguments] (required) - List of command line arguments
   and substitutions

3. [:name] - Simple name (e.g. "nickname") of tool beyond its
   executable name (if not explicitly set then Ceedling will
   form a name from the tool's YAML entry name)

4. [:stderr_redirect] - Control of capturing $stderr messages
   {:none, :auto, :win, :unix, :tcsh}.
   Defaults to :none if unspecified; create a custom entry by
   specifying a simple string instead of any of the available
   symbols.

5. [:background_exec] - Control execution as background process
   {:none, :auto, :win, :unix}.
   Defaults to :none if unspecified.


Tool Element Runtime Substitution
---------------------------------

To accomplish useful work on multiple files, a configured tool will most
often require that some number of its arguments or even the executable
itself change for each run. Consequently, every tool's argument list and
executable field possess two means for substitution at runtime. Ceedling
provides two kinds of inline Ruby execution and a notation for
populating elements with dynamically gathered values within the build
environment.

Tool Element Runtime Substitution: Inline Ruby Execution
--------------------------------------------------------

In-line Ruby execution works similarly to that demonstrated for the
[:environment] section except that substitution occurs as the tool is
executed and not at the time the configuration file is first scanned.

* `#{...}`:

  Ruby string substitution pattern wherein the containing string is
  expanded to include the string generated by Ruby code between the
  braces. Multiple instances of this expansion can occur within a single
  tool element entry string. Note that if this string substitution
  pattern occurs at the very beginning of a string in the YAML
  configuration the entire string should be enclosed in quotes (see the
  [:environment] section for further explanation on this point).

* `{...} `:

  If an entire tool element string is enclosed with braces, it signifies
  that Ceedling should execute the Ruby code contained within those
  braces. Say you have a collection of paths on disk and some of those
  paths include spaces. Further suppose that a single tool that must use
  those paths requires those spaces to be escaped, but all other uses of
  those paths requires the paths to remain unchanged. You could use this
  Ceedling feature to insert Ruby code that iterates those paths and
  escapes those spaces in the array as used by the tool of this example.

Tool Element Runtime Substitution: Notational Substitution
----------------------------------------------------------

A Ceedling tool's other form of dynamic substitution relies on a '$'
notation. These '$' operators can exist anywhere in a string and can be
decorated in any way needed. To use a literal '$', escape it as '\\$'.

* `$`:

  Simple substitution for value(s) globally available within the runtime
  (most often a string or an array).

* `${#}`:

  When a Ceedling tool's command line is expanded from its configured
  representation and used within Ceedling Ruby code, certain calls to
  that tool will be made with a parameter list of substitution values.
  Each numbered substitution corresponds to a position in a parameter
  list. Ceedling Ruby code expects that configured compiler and linker
  tools will contain ${1} and ${2} replacement arguments. In the case of
  a compiler ${1} will be a C code file path, and ${2} will be the file
  path of the resulting object file. For a linker ${1} will be an array
  of object files to link, and ${2} will be the resulting binary
  executable. For an executable test fixture ${1} is either the binary
  executable itself (when using a local toolchain such as gcc) or a
  binary input file given to a simulator in its arguments.


Example [:tools] YAML blurbs

```yaml
:tools:
  :test_compiler:
     :executable: compiler              #exists in system search path
     :name: 'acme test compiler'
     :arguments:
        - -I"$": COLLECTION_PATHS_TEST_TOOLCHAIN_INCLUDE               #expands to -I search paths
        - -I"$": COLLECTION_PATHS_TEST_SUPPORT_SOURCE_INCLUDE_VENDOR   #expands to -I search paths
        - -D$: COLLECTION_DEFINES_TEST_AND_VENDOR  #expands to all -D defined symbols
        - --network-license             #simple command line argument
        - -optimize-level 4             #simple command line argument
        - "#{`args.exe -m acme.prj`}"   #in-line ruby sub to shell out & build string of arguments
        - -c ${1}                       #source code input file (Ruby method call param list sub)
        - -o ${2}                       #object file output (Ruby method call param list sub)
  :test_linker:
     :executable: /programs/acme/bin/linker.exe    #absolute file path
     :name: 'acme test linker'
     :arguments:
        - ${1}               #list of object files to link (Ruby method call param list sub)
        - -l$-lib:           #inline yaml array substitution to link in foo-lib and bar-lib
           - foo
           - bar
        - -o ${2}            #executable file output (Ruby method call param list sub)
  :test_fixture:
     :executable: tools/bin/acme_simulator.exe  #relative file path to command line simulator
     :name: 'acme test fixture'
     :stderr_redirect: :win                     #inform Ceedling what model of $stderr capture to use
     :arguments:
        - -mem large   #simple command line argument
        - -f "${1}"    #binary executable input file to simulator (Ruby method call param list sub)
```

Resulting command line constructions from preceding example [:tools] YAML blurbs

    > compiler -I"/usr/include” -I”project/tests”
      -I"project/tests/support” -I”project/source” -I”project/include”
      -DTEST -DLONG_NAMES -network-license -optimize-level 4 arg-foo
      arg-bar arg-baz -c project/source/source.c -o
      build/tests/out/source.o

[notes: (1.) "arg-foo arg-bar arg-baz" is a fabricated example
string collected from $stdout as a result of shell execution
of args.exe
(2.) the -c and -o arguments are
fabricated examples simulating a single compilation step for
a test; ${1} & ${2} are single files]

    > \programs\acme\bin\linker.exe thing.o unity.o
      test_thing_runner.o test_thing.o mock_foo.o mock_bar.o -lfoo-lib
      -lbar-lib -o build\tests\out\test_thing.exe

[note: in this scenario ${1} is an array of all the object files
needed to link a test fixture executable]

    > tools\bin\acme_simulator.exe -mem large -f "build\tests\out\test_thing.bin 2>&1”

[note: (1.) :executable could have simply been ${1} - if we were compiling
and running native executables instead of cross compiling (2.) we're using
$stderr redirection to allow us to capture simulator error messages to
$stdout for display at the run's conclusion]


Notes:

* The upper case names are Ruby global constants that Ceedling
  builds

* "COLLECTION_" indicates that Ceedling did some work to assemble
  the list. For instance, expanding path globs, combining multiple
  path globs into a convenient summation, etc.

* At present, $stderr redirection is primarily used to capture
  errors from test fixtures so that they can be displayed at the
  conclusion of a test run. For instance, if a simulator detects
  a memory access violation or a divide by zero error, this notice
  might go unseen in all the output scrolling past in a terminal.

* The preprocessing tools can each be overridden with non-gcc
  equivalents. However, this is an advanced feature not yet
  documented and requires that the replacement toolchain conform
  to the same conventions used by gcc.

**Ceedling Collection Used in Compilation**:

* `COLLECTION_PATHS_TEST`:

  All test paths

* `COLLECTION_PATHS_SOURCE`:

  All source paths

* `COLLECTION_PATHS_INCLUDE`:

  All include paths

* `COLLECTION_PATHS_SUPPORT`:

  All test support paths

* `COLLECTION_PATHS_SOURCE_AND_INCLUDE`:

  All source and include paths

* `COLLECTION_PATHS_SOURCE_INCLUDE_VENDOR`:

  All source and include paths + applicable vendor paths (e.g.
  CException's source path if exceptions enabled)

* `COLLECTION_PATHS_TEST_TOOLCHAIN_INCLUDE`:

  All test toolchain include paths

* `COLLECTION_PATHS_TEST_SUPPORT_SOURCE_INCLUDE`:

  All test, source, and include paths

* `COLLECTION_PATHS_TEST_SUPPORT_SOURCE_INCLUDE_VENDOR`:

  All test, source, include, and applicable vendor paths (e.g. Unity's
  source path plus CMock and CException's source paths if mocks and
  exceptions are enabled)

* `COLLECTION_PATHS_RELEASE_TOOLCHAIN_INCLUDE`:

  All release toolchain include paths

* `COLLECTION_DEFINES_TEST_AND_VENDOR`:

  All symbols specified in [:defines][:test] + symbols defined for
  enabled vendor tools - e.g. [:unity][:defines], [:cmock][:defines],
  and [:cexception][:defines]

* `COLLECTION_DEFINES_RELEASE_AND_VENDOR`:

  All symbols specified in [:defines][:release] plus symbols defined by
[:cexception][:defines] if exceptions are ena bled


Notes:

* Other collections exist within Ceedling. However, they are
  only useful for advanced features not yet documented.

* Wherever multiple path lists are combined for use Ceedling prioritizes
  path groups as follows: test paths, support paths, source paths, include
  paths.
  This can be useful, for instance, in certain testing scenarios
  where we desire Ceedling or the compiler to find a stand-in header file
  before the actual source header file of the same name.


**plugins**: Ceedling extensions

* `load_paths`:

  Base paths to search for plugin subdirectories or extra ruby functionalit

  **Default**: [] (empty)

* `enabled`:

  List of plugins to be used - a plugin's name is identical to the
  subdirectory that contains it (and the name of certain files within
  that subdirectory)

  **Default**: [] (empty)


Plugins can provide a variety of added functionality to Ceedling. In
general use, it's assumed that at least one reporting plugin will be
used to format test results. However, if no reporting plugins are
specified, Ceedling will print to `$stdout` the (quite readable) raw
test results from all test fixtures executed.

Example [:plugins] YAML blurb

```yaml
:plugins:
  :load_paths:
    - project/tools/ceedling/plugins  #home to your collection of plugin directories
    - project/support                 #maybe home to some ruby code your custom plugins share
  :enabled:
    - stdout_pretty_tests_report      #nice test results at your command line
    - our_custom_code_metrics_report  #maybe you needed line count and complexity metrics, so you
                                      #created a plugin to scan all your code and collect that info
```

* `stdout_pretty_tests_report`:

  Prints to $stdout a well-formatted list of ignored and failed tests,
  final test counts, and any extraneous output (e.g. printf statements
  or simulator memory errors) collected from executing the test
  fixtures. Meant to be used with runs at the command line.

* `stdout_ide_tests_report`:

  Prints to $stdout simple test results formatted such that an IDE
  executing test-related Rake tasks can recognize file paths and line
  numbers in test failures, etc. Thus, you can click a test result in
  your IDE's execution window and jump to the failure (or ignored test)
  in your test file (obviously meant to be used with an [IDE like
  Eclipse][ide], etc).

  [ide]: http://throwtheswitch.org/white-papers/using-with-ides.html

* `xml_tests_report`:

  Creates an XML file of test results in the xUnit format (handy for
  Continuous Integration build servers or as input to other reporting
  tools). Produces a file report.xml in <build root>/artifacts/tests.

* `bullseye`:

  Adds additional Rake tasks to execute tests with the commercial code
  coverage tool provided by [Bullseye][]. See readme.txt inside the bullseye
  plugin directory for configuration and use instructions. Note:
  Bullseye only works with certain compilers and linkers (healthy list
  of supported toolchains though).

  [bullseye]: http://www.bullseye.com

* `gcov`:

  Adds additional Rake tasks to execute tests with the GNU code coverage
  tool [gcov][]. See readme.txt inside the gcov directory for configuration
  and use instructions. Only works with GNU compiler and linker.

  [gcov]: http://gcc.gnu.org/onlinedocs/gcc/Gcov.html

* `warnings_report`:

  Scans compiler and linker `$stdout / $stderr` output for the word
  'warning' (case insensitive). All code warnings (or tool warnings) are
  logged to a file warnings.log in the appropriate `<build
  root>/artifacts` directory (e.g. test/ for test tasks, `release/` for a
  release build, or even `bullseye/` for bullseye runs).

Module Generator
========================
Ceedling includes a plugin called module_generator that will create a source, header and test file for you.
There are several possibilities to configure this plugin through your project.yml to suit your project's needs.

Directory Structure
-------------------------------------------

The default configuration for directory/project structure is:
```yaml
:module_generator:
  :project_root: ./
  :source_root: src/
  :test_root: test/
```
You can change these variables in your project.yml file to comply with your project's directory structure.

If you call `ceedling module:create`, it will create three files:
1. A source file in the source_root
2. A header file in the source_root
3. A test file in the test_root

If you want your header file to be in another location,
you can specify the ':inc_root:" in your project.yml file:
```yaml
:module_generator:
  :inc_root: inc/
```
The module_generator will then create the header file in your defined ':inc_root:'.
By default, ':inc_root:' is not defined so the module_generator will use the source_root.

Sometimes, your project can't be divided into a single src, inc, and test folder. You have several directories
with sources/..., something like this for example:
<project_root>
 - myDriver
   - src
   - inc
   - test
 - myOtherDriver
   - src
   - inc
   - test
 - ...

Don't worry, you don't have to manually create the source/header/test files.
The module_generator can accept a path to create a source_root/inc_root/test_root folder with your files:
`ceedling module:create[<module_root_path>:<module_name>]`

F.e., applied to the above project structure:
`ceedling module:create[myOtherDriver:driver]`
This will make the module_generator run in the subdirectory 'myOtherDriver' and generate the module files
for you in that directory. So, this command will generate the following files:
1. A source file 'driver.c' in <project_root>/myOtherDriver/<source_root>
2. A header file 'driver.h' in <project_root>/myOtherDriver/<source_root> (or <inc_root> if specified)
3. A test file 'test_driver.c' in <project_root>/myOtherDriver/<test_root>

Naming
-------------------------------------------
By default, the module_generator will generate your files in lowercase.
`ceedling module:create[mydriver]` and `ceedling module:create[myDriver]`(note the uppercase) will generate the same files:
1. mydriver.c
2. mydriver.h
3. test_mydriver.c

You can configure the module_generator to use a differect naming mechanism through the project.yml:
```yaml
:module_generator:
  :naming: "camel"
```
There are other possibilities as well (bumpy, camel, snake, caps).
Refer to the unity module generator for more info (the unity module generator is used under the hood by module_generator).

Advanced Topics (Coming)
========================

Modifying Your Configuration without Modifying Your Project File: Option Files & User Files
-------------------------------------------------------------------------------------------

Modifying your project file without modifying your project file

Debugging and/or printf()
-------------------------

When you gotta get your hands dirty...

Ceedling Plays Nice with Others - Using Ceedling for Tests Alongside Another Release Build Setup
------------------------------------------------------------------------------------------------

You've got options.

Adding Handy Rake Tasks for Your Project (without Fancy Pants Custom Plugins)
-----------------------------------------------------------------------------

Simple as snot.

Working with Non-Desktop Testing Environments
---------------------------------------------

For those crazy platforms lacking command line simulators and for which
cross-compiling on the desktop just ain't gonna get it done.

Creating Custom Plugins
-----------------------

Oh boy. This is going to take some explaining.