<p>I worked on an embedded system this summer written in straight C.  It was an existing project that the company I work for had taken over.  I have become quite accustomed to writing unit tests in Java using JUnit but was at a loss as to the best way to write unit tests for existing code (which needed refactoring) as well as new code added to the system.</p>

<p>Are there any projects out there that make unit testing plain C code as easy as unit testing Java code with JUnit?  Any insight that would apply specifically to embedded development (cross-compiling to arm-linux platform) would be greatly appreciated.</p>

One unit testing framework in C is
Check
; a list of unit testing frameworks in C can be found
here
and is reproduced below.  Depending on how many standard library functions your runtime has, you may or not be able to use one of those.
AceUnit
AceUnit (Advanced C and Embedded Unit) bills itself as a comfortable C code unit test framework. It tries to mimick JUnit 4.x and includes reflection-like capabilities. AceUnit can be used in resource constraint environments, e.g. embedded software development, and importantly it runs fine in environments where you cannot include a single standard header file and cannot invoke a single standard C function from the ANSI / ISO C libraries. It also has a Windows port. It does not use forks to trap signals, although the authors have expressed interest in adding such a feature. See the
AceUnit homepage
.
GNU Autounit
Much along the same lines as Check, including forking to run unit tests in a separate address space (in fact, the original author of Check borrowed the idea from GNU Autounit). GNU Autounit uses GLib extensively, which means that linking and such need special options, but this may not be a big problem to you, especially if you are already using GTK or GLib. See the
GNU Autounit homepage
.
cUnit
Also uses GLib, but does not fork to protect the address space of unit tests.
CUnit
Standard C, with plans for a Win32 GUI implementation. Does not currently fork or otherwise protect the address space of unit tests. In early development. See the
CUnit homepage
.
CuTest
A simple framework with just one .c and one .h file that you drop into your source tree. See the
CuTest homepage
.
CppUnit
The premier unit testing framework for C++; you can also use it to test C code. It is stable, actively developed, and has a GUI interface. The primary reasons not to use CppUnit for C are first that it is quite big, and second you have to write your tests in C++, which means you need a C++ compiler. If these don’t sound like concerns, it is definitely worth considering, along with other C++ unit testing frameworks. See the
CppUnit homepage
.
embUnit
embUnit (Embedded Unit) is another unit test framework for embedded systems. This one appears to be superseded by AceUnit.
Embedded Unit homepage
.
MinUnit
A minimal set of macros and that’s it! The point is to show how easy it is to unit test your code. See the
MinUnit homepage
.
CUnit for Mr. Ando
A CUnit implementation that is fairly new, and apparently still in early development. See the
CUnit for Mr. Ando homepage
.
This list was last updated in March 2008.
More frameworks:
CMocka
CMocka is a test framework for C with support for mock objects. It's easy to use and setup.
See
the CMocka homepage
.
Criterion
Criterion is a cross-platform C unit testing framework supporting automatic test registration, parameterized tests, theories, and that can output to multiple formats, including TAP and JUnit XML. Each test is run in its own process, so signals and crashes can be reported or tested if needed.
See the
Criterion homepage
for more information.
HWUT
HWUT is a general Unit Test tool with great support for C. It can help to create Makefiles, generate massive test cases coded in minimal 'iteration tables', walk along state machines, generate C-stubs and more. The general approach is pretty unique: Verdicts are based on 'good stdout/bad stdout'. The comparison function, though, is flexible. Thus, any type of script may be used for checking. It may be applied to any language that can produce standard output.
See
the HWUT homepage
.
CGreen
A modern, portable, cross-language unit testing and mocking framework for C and C++. It offers an optional BDD notation, a mocking library, the ability to run it in a single process (to make debugging easier). A test runner which discover automatically the test functions is available. But you can create your own programmatically.
All those features (and more) are explained in
the CGreen manual
.
Wikipedia gives a detailed list of C unit testing frameworks under
List of unit testing frameworks: C