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The Cutest C Unit Testing Framework

Project README

How To Use

You can use CuTest to create unit tests to drive your development in the style of Extreme Programming. You can also add unit tests to existing code to ensure that it works as you suspect.

Your unit tests are an investment. They let you to change your code and add new features confidently without worrying about accidentally breaking earlier features.


For details on licensing see license.txt.

Getting Started

To add unit testing to your C code the only files you need are CuTest.c and CuTest.h.

CuTestTest.c and AllTests.c have been included to provide an example of how to write unit tests and then how to aggregate them into suites and into a single AllTests.c file. Suites allow you to put group tests into logical sets. AllTests.c combines all the suites and runs them.

You should not have to look inside CuTest.c. Looking in CuTestTest.c and AllTests.c (for example usage) should be sufficient.

After downloading the sources, run your compiler to create an executable called AllTests.exe. For example, if you are using Windows with the cl.exe compiler you would type:

cl.exe AllTests.c CuTest.c CuTestTest.c

On Unix you should type:

gcc AllTests.c CuTest.c CuTestTest.c

This will run all the unit tests associated with CuTest and print the output on the console. You can replace cl.exe with gcc or your favorite compiler in the command above.

Detailed Example

Here is a more detailed example. We will work through a simple test first exercise. The goal is to create a library of string utilities. First, lets write a function that converts a null-terminated string to all upper case.

Ensure that CuTest.c and CuTest.h are accessible from your C project. Next, create a file called StrUtil.c with these contents:

#include "CuTest.h"

char* StrToUpper(char* str) {
    return str;

void TestStrToUpper(CuTest *tc) {
    char* input = strdup("hello world");
    char* actual = StrToUpper(input);
    char* expected = "HELLO WORLD";
    CuAssertStrEquals(tc, expected, actual);

CuSuite* StrUtilGetSuite() {
    CuSuite* suite = CuSuiteNew();
    SUITE_ADD_TEST(suite, TestStrToUpper);
    return suite;

Create another file called AllTests.c with these contents:

#include "CuTest.h"

CuSuite* StrUtilGetSuite();

void RunAllTests(void) {
    CuString *output = CuStringNew();
    CuSuite* suite = CuSuiteNew();
    CuSuiteAddSuite(suite, StrUtilGetSuite());

    CuSuiteSummary(suite, output);
    CuSuiteDetails(suite, output);
    printf("%s\n", output->buffer);

int main(void) {

Then type this on the command line:

gcc AllTests.c CuTest.c StrUtil.c

to compile. You can replace gcc with your favorite compiler. CuTest should be portable enough to handle all Windows and Unix compilers. Then to run the tests type:


This will print an error because we haven't implemented the StrToUpper function correctly. We are just returning the string without changing it to upper case.

char* StrToUpper(char* str) {
    return str;

Rewrite this as follows:

char* StrToUpper(char* str) {
    char* p;
    for (p = str ; *p ; ++p) *p = toupper(*p);
    return str;

Recompile and run the tests again. The test should pass this time.

What To Do Next

At this point you might want to write more tests for the StrToUpper function. Here are some ideas:

TestStrToUpper_EmptyString /* pass in ""            */
TestStrToUpper_UpperCase   /* pass in "HELLO WORLD" */
TestStrToUpper_MixedCase   /* pass in "HELLO world" */
TestStrToUpper_Numbers     /* pass in "1234 hello"  */

As you write each one of these tests add it to StrUtilGetSuite function. If you don't the tests won't be run. Later as you write other functions and write tests for them be sure to include those in StrUtilGetSuite also. The StrUtilGetSuite function should include all the tests in StrUtil.c

Over time you will create another file called FunkyStuff.c containing other functions unrelated to StrUtil. Follow the same pattern. Create a FunkyStuffGetSuite function in FunkyStuff.c. And add FunkyStuffGetSuite to AllTests.c.

The framework is designed in the way it is so that it is easy to organize a lot of tests.

The Big Picture

Each individual test corresponds to a CuTest. These are grouped to form a CuSuite. CuSuites can hold CuTests or other CuSuites. AllTests.c collects all the CuSuites in the program into a single CuSuite which it then runs as a single CuSuite.

The project is open source so feel free to take a peek under the hood at the CuTest.c file to see how it works. CuTestTest.c contains tests for CuTest.c. So CuTest tests itself.

Since AllTests.c has a main() you will need to exclude this when you are building your product. Here is a nicer way to do this if you want to avoid messing with multiple builds. Remove the main() in AllTests.c. Note that it just calls RunAllTests(). Instead we'll call this directly from the main program.

Now in the main() of the actual program check to see if the command line option "--test" was passed. If it was then I call RunAllTests() from AllTests.c. Otherwise run the real program.

Shipping the tests with the code can be useful. If you customers complain about a problem you can ask them to run the unit tests and send you the output. This can help you to quickly isolate the piece of your system that is malfunctioning in the customer's environment.

CuTest offers a rich set of CuAssert functions. Here is a list:

void CuAssert(CuTest* tc, char* message, int condition);
void CuAssertTrue(CuTest* tc, int condition);
void CuAssertStrEquals(CuTest* tc, char* expected, char* actual);
void CuAssertIntEquals(CuTest* tc, int expected, int actual);
void CuAssertPtrEquals(CuTest* tc, void* expected, void* actual);
void CuAssertPtrNotNull(CuTest* tc, void* pointer);

The project is open source and so you can add other more powerful asserts to make your tests easier to write and more concise. Please feel free to send me changes you make so that I can incorporate them into future releases.

If you see any errors in this document please contact me at [email protected].

Automating Test Suite Generation will grep through all the .c files in the current directory and generate the code to run all the tests contained in them. Using this script you don't have to worry about writing AllTests.c or dealing with any of the other suite code.


[02.23.2003] Dave Glowacki [email protected] has added (1) file name and line numbers to the error messages, (2) AssertDblEquals for doubles, (3) Assert<X>Equals_Msg version of all the Assert<X>Equals to pass in optional message which is printed out on assert failure.

Open Source Agenda is not affiliated with "Asimjalis Cutest" Project. README Source: asimjalis/cutest
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