Simple header-only C/C++ unit testing facility.
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Acutest Readme


What Is Acutest

"Acutest" means "Another C Unit Testing" and it is intended to do exactly that, while being as simple as possible to use it, not to stand in the developer's way and minimize any external dependencies.

To achieve that, the complete implementation resides in a single C header file, and its core depends only on few standard C library functions.

Acutest supports C as well as C++, and it can deal with unit tests which throw C++ exceptions.


Main features:

  • Unit tests in C or C++ are supported.
  • No need to install/setup/configure testing framework. Acutest is just single C/C++ header, "acutest.h".
  • The header provides program entry point (function main()).
  • Minimal dependencies: Core features only depend on few standard C headers, optional features may use more if available on the particular system.
  • Trivial interface for writing unit tests: Few preprocessor macros described further below.

Windows specific features:

  • By default, every unit test is executed as a child process.
  • By default, if the output is directed to a terminal, the output is colorized.
  • Acutest installs a SEH filter to print out uncaught SEH exceptions.

Unix specific features:

  • By default, every unit test is executed as a child process.
  • By default, if the output is directed to a terminal, the output is colorized.

C++ specific features:

  • Acutest catches C++ exceptions thrown from unit test functions. Such unit tests are considered to fail.
  • If the exception is derived from std::exception, what() is written out in the error message.

Any C/C++ module implementing one or more unit tests and including "acutest.h", can be built as a standalone program. We call the resulted binary as a "test suite" for purposes of this document. The suite is then executed to run the tests, as specified with its command line options.

By default, all unit tests in the program are run and (on Windows and Unix) every unit test is executed in a context of its own subprocess. Both can be overridden on the command line.

We say any unit test succeeds if all conditions (preprocessor macros TEST_CHECK or TEST_CHECK_) called throughout its execution pass, the test does not throw an exception (C++ only), and (on Windows/Unix) the unit test subprocess is not interrupted/terminated (e.g. by a signal on Unix or SEH on Windows).

Exit code of the test suite is 0 if all unit tests pass, 1 if any of them fails, or other number if an internal error occurs.

Writing Unit Tests

To use Acutest, simply include the header file "acutest.h" on the beginning of the C/C++ source file implementing one or more unit tests. Note the header provides implementation of the main() function.

#include "acutest.h"

Every test is supposed to be implemented as a function with the following prototype:

void test_example(void);

The tests can use preprocessor macro TEST_CHECK or TEST_CHECK_ to validate the test conditions. They can be used multiple times, and if any of those conditions fails, the particular test is considered to fail.

(The macro TEST_CHECK_ can be used only if your C preprocessor supports variadic macros: it takes printf-like extra arguments to provide a custom error message if the condition fails.)

For example:

void test_example(void)
    void* mem;
    int a, b;

    mem = malloc(10);
    TEST_CHECK(mem != NULL);

    mem = realloc(mem, 20);
    TEST_CHECK(mem != NULL);

    a = 1;
    b = 2;
    TEST_CHECK_(a + b == 3, "Expected %d, got %d", 3, a + b);

Note that the tests should be independent on each other. Whenever the test suite is invoked, the user may run any number of tests in the suite, in any order. Furthermore by default, on platforms where supported, each unit test is executed as a standalone (sub)process.

Finally, the test suite source file has to list the unit tests, using the macro TEST_LIST. The list specifies name of each test (it has to be unique) and pointer to a function implementing the test. I recommend names which are easy to use on command line, i.e. especially avoid space and other special characters in them. Also avoid using dash as a first character, as it would be then interpreted as a command line option, not a test name.

   { "example", test_example },
   { 0 }

Note the test list has to be ended with zeroed record.

Finally you just compile the C/C++ test suite source file as a simple program. For example, assuming cc is your C compiler:

$ cc test_example.c -o test_example

More comprehensive description of API can be found in comments in the header "acutest.h".

Running Unit Tests

When the source file implementing the tests is compiled, the resulted testing binary can be used to run the tests.

By default (without any command line options), it runs all implemented unit tests. It can also run only subset of the unit tests as specified on the command line:

$ ./test_example                # Runs all tests in the suite
$ ./test_example test1 test2    # Runs only tests specified
$ ./test_example --skip test3   # Runs all tests but those specified

Acutest implements several levels of unit test selection. Note the first rule which successfully finds non-empty set of unit tests applies:

  1. Exact match: Applies when the command line argument matches exactly name of any unit test.

  2. Word match: Applies when the command line argument matches whole word of any unit test. (Space , tabulator \t, dash - and underscore _ are understood as word delimiters in test names.)

  3. Relaxed match: Applies when the command line argument matches any substring in name of unit test.

By adopting an appropriate test naming strategy, this allows user to run (or to skip if --skip is used) whole groups of related tests with a single command line argument. For example consider test suite test_example which implements tests foo-1, foo-2, foomatic, bar-1 and bar-10:

$ ./test_example bar-1   # Runs only the test 'bar-1' (exact match)
$ ./test_example foo     # Runs 'foo-1' and 'foo-2' (word match)
$ ./test_example oo      # Runs 'foo-1', 'foo-2' and 'foomatic' (relaxed match)
$ ./test_example 1       # Runs 'foo-1' and 'bar-1' (word match)

You may use --list or -l to just list all unit tests implemented by the given test suite:

$ ./test_example --list

To see all the supported command line options, run the binary with the option --help:

$ ./test_example --help


Q: Wasn't this project known as "CUTest"?

A: Yes. It has been renamed as the original name was too much overloaded.


Acutest is covered with MIT license, see the file or beginning of "acutest.h" for its full text.

More Information

The project resides on github:

You can find the latest version of Acutest there, contribute with enhancements or report bugs.