t/unit-tests/clar/README.md

Come out and Clar
=================

In Catalan, "clar" means clear, easy to perceive.  Using clar will make it
easy to test and make clear the quality of your code.

> _Historical note_
>
> Originally the clar project was named "clay" because the word "test" has its
> roots in the latin word *"testum"*, meaning "earthen pot", and *"testa"*,
> meaning "piece of burned clay"?
>
> This is because historically, testing implied melting metal in a pot to
> check its quality.  Clay is what tests are made of.

## Quick Usage Overview

Clar is a minimal C unit testing framework. It's been written to replace the
old framework in [libgit2][libgit2], but it's both very versatile and
straightforward to use.

Can you count to funk?

- **Zero: Initialize test directory**

    ~~~~ sh
    $ mkdir tests
    $ cp -r $CLAR_ROOT/clar* tests
    $ cp $CLAR_ROOT/example/*.c tests
    ~~~~

- **One: Write some tests**

    File: tests/adding.c:

    ~~~~ c
    /* adding.c for the "Adding" suite */
    #include "clar.h"

    static int *answer;

    void test_adding__initialize(void)
    {
        answer = malloc(sizeof(int));
        cl_assert_(answer != NULL, "No memory left?");
        *answer = 42;
    }

    void test_adding__cleanup(void)
    {
        free(answer);
    }

    void test_adding__make_sure_math_still_works(void)
    {
        cl_assert_(5 > 3, "Five should probably be greater than three");
        cl_assert_(-5 < 2, "Negative numbers are small, I think");
        cl_assert_(*answer == 42, "The universe is doing OK. And the initializer too.");
    }
    ~~~~~

- **Two: Build the test executable**

    ~~~~ sh
    $ cd tests
    $ $CLAR_PATH/generate.py .
    Written `clar.suite` (1 suites)
    $ gcc -I. clar.c main.c adding.c -o testit
    ~~~~

- **Funk: Funk it.**

    ~~~~ sh
    $ ./testit
    ~~~~

## The Clar Test Suite

Writing a test suite is pretty straightforward. Each test suite is a `*.c`
file with a descriptive name: this encourages modularity.

Each test suite has optional initialize and cleanup methods. These methods
will be called before and after running **each** test in the suite, even if
such test fails. As a rule of thumb, if a test needs a different initializer
or cleanup method than another test in the same module, that means it
doesn't belong in that module. Keep that in mind when grouping tests
together.

The `initialize` and `cleanup` methods have the following syntax, with
`suitename` being the current suite name, e.g. `adding` for the `adding.c`
suite.

~~~~ c
void test_suitename__initialize(void)
{
    /* init */
}

void test_suitename__cleanup(void)
{
    /* cleanup */
}
~~~~

These methods are encouraged to use static, global variables to store the state
that will be used by all tests inside the suite.

~~~~ c
static git_repository *_repository;

void test_status__initialize(void)
{
    create_tmp_repo(STATUS_REPO);
    git_repository_open(_repository, STATUS_REPO);
}

void test_status__cleanup(void)
{
    git_repository_close(_repository);
    git_path_rm(STATUS_REPO);
}

void test_status__simple_test(void)
{
    /* do something with _repository */
}
~~~~

Writing the actual tests is just as straightforward. Tests have the
`void test_suitename__test_name(void)` signature, and they should **not**
be static. Clar will automatically detect and list them.

Tests are run as they appear on their original suites: they have no return
value. A test is considered "passed" if it doesn't raise any errors. Check
the "Clar API" section to see the various helper functions to check and
raise errors during test execution.

__Caution:__ If you use assertions inside of `test_suitename__initialize`,
make sure that you do not rely on `__initialize` being completely run
inside your `test_suitename__cleanup` function. Otherwise you might
encounter resource cleanup twice.

## How does Clar work?

To use Clar:

1. copy the Clar boilerplate to your test directory
2. copy (and probably modify) the sample `main.c` (from
   `$CLAR_PATH/example/main.c`)
3. run the Clar mixer (a.k.a. `generate.py`) to scan your test directory and
   write out the test suite metadata.
4. compile your test files and the Clar boilerplate into a single test
   executable
5. run the executable to test!

The Clar boilerplate gives you a set of useful test assertions and features
(like accessing or making sandbox copies of fixture data).  It consists of
the `clar.c` and `clar.h` files, plus the code in the `clar/` subdirectory.
You should not need to edit these files.

The sample `main.c` (i.e. `$CLAR_PATH/example/main.c`) file invokes
`clar_test(argc, argv)` to run the tests.  Usually, you will edit this file
to perform any framework specific initialization and teardown that you need.

The Clar mixer (`generate.py`) recursively scans your test directory for
any `.c` files, parses them, and writes the `clar.suite` file with all of
the metadata about your tests.  When you build, the `clar.suite` file is
included into `clar.c`.

The mixer can be run with **Python 2.5, 2.6, 2.7, 3.0, 3.1, 3.2 and PyPy 1.6**.

Commandline usage of the mixer is as follows:

    $ ./generate.py .

Where `.` is the folder where all the test suites can be found. The mixer
will automatically locate all the relevant source files and build the
testing metadata. The metadata will be written to `clar.suite`, in the same
folder as all the test suites. This file is included by `clar.c` and so
must be accessible via `#include` when building the test executable.

    $ gcc -I. clar.c main.c suite1.c test2.c -o run_tests

**Note that the Clar mixer only needs to be ran when adding new tests to a
suite, in order to regenerate the metadata**. As a result, the `clar.suite`
file can be checked into version control if you wish to be able to build
your test suite without having to re-run the mixer.

This is handy when e.g. generating tests in a local computer, and then
building and testing them on an embedded device or a platform where Python
is not available.

### Fixtures

Clar can create sandboxed fixtures for you to use in your test. You'll need to compile *clar.c* with an additional `CFLAG`, `-DCLAR_FIXTURE_PATH`. This should be an absolute path to your fixtures directory.

Once that's done, you can use the fixture API as defined below.

## The Clar API

Clar makes the following methods available from all functions in a test
suite.

-   `cl_must_pass(call)`, `cl_must_pass_(call, message)`: Verify that the given
    function call passes, in the POSIX sense (returns a value greater or equal
    to 0).

-   `cl_must_fail(call)`, `cl_must_fail_(call, message)`: Verify that the given
    function call fails, in the POSIX sense (returns a value less than 0).

-   `cl_assert(expr)`, `cl_assert_(expr, message)`: Verify that `expr` is true.

-   `cl_check_pass(call)`, `cl_check_pass_(call, message)`: Verify that the
    given function call passes, in the POSIX sense (returns a value greater or
    equal to 0). If the function call doesn't succeed, a test failure will be
    logged but the test's execution will continue.

-   `cl_check_fail(call)`, `cl_check_fail_(call, message)`: Verify that the
    given function call fails, in the POSIX sense (returns a value less than
    0). If the function call doesn't fail, a test failure will be logged but
    the test's execution will continue.

-   `cl_check(expr)`: Verify that `expr` is true. If `expr` is not
    true, a test failure will be logged but the test's execution will continue.

-   `cl_fail(message)`: Fail the current test with the given message.

-   `cl_warning(message)`: Issue a warning. This warning will be
    logged as a test failure but the test's execution will continue.

-   `cl_set_cleanup(void (*cleanup)(void *), void *opaque)`: Set the cleanup
    method for a single test. This method will be called with `opaque` as its
    argument before the test returns (even if the test has failed).
    If a global cleanup method is also available, the local cleanup will be
    called first, and then the global.

-   `cl_assert_equal_i(int,int)`: Verify that two integer values are equal.
    The advantage of this over a simple `cl_assert` is that it will format
    a much nicer error report if the values are not equal.

-   `cl_assert_equal_s(const char *,const char *)`: Verify that two strings
    are equal.  The expected value can also be NULL and this will correctly
    test for that.

-   `cl_fixture_sandbox(const char *)`: Sets up a sandbox for a fixture
    so that you can mutate the file directly.

-   `cl_fixture_cleanup(const char *)`: Tears down the previous fixture
    sandbox.

-   `cl_fixture(const char *)`: Gets the full path to a fixture file.

### Auxiliary / helper functions

The clar API is always available while running a test, even when calling
"auxiliary" (helper) functions.

You're encouraged to perform test assertions in those auxiliary
methods, instead of returning error values. This is considered good
Clar style. _However_, when you do this, you need to call `cl_invoke`
to preserve the current state; this ensures that failures are reported
as coming from the actual test, instead of the auxiliary method.

Style Example:

~~~~ c
/*
 * Bad style: auxiliary functions return an error code
 */

static int check_string(const char *str)
{
    const char *aux = process_string(str);

    if (aux == NULL)
        return -1;

    return strcmp(my_function(aux), str) == 0 ? 0 : -1;
}

void test_example__a_test_with_auxiliary_methods(void)
{
    cl_must_pass_(
        check_string("foo"),
        "String differs after processing"
    );

    cl_must_pass_(
        check_string("bar"),
        "String differs after processing"
    );
}
~~~~

~~~~ c
/*
 * Good style: auxiliary functions perform assertions
 */

static void check_string(const char *str)
{
    const char *aux = process_string(str);

    cl_assert_(
        aux != NULL,
        "String processing failed"
    );

    cl_assert_(
        strcmp(my_function(aux), str) == 0,
        "String differs after processing"
    );
}

void test_example__a_test_with_auxiliary_methods(void)
{
    cl_invoke(check_string("foo"));
    cl_invoke(check_string("bar"));
}
~~~~

About Clar
==========

Clar was originally written by [Vicent Martí](https://github.com/vmg),
to replace the old testing framework in [libgit2][libgit2]. It is
currently maintained by [Edward Thomson](https://github.com/ethomson),
and used by the [libgit2][libgit2] and [git][git] projects, amongst
others.

[libgit2]: https://github.com/libgit2/libgit2
[git]: https://github.com/git/git