Unit Testing framework for C

[Free]
CuTest
http://cutest.sourceforge.net/

Check
http://check.sourceforge.net/

MinUnit
http://www.jera.com/techinfo/jtns/jtn002.html

[Commercial]
C++Test
http://www.parasoft.com/jsp/products/home.jsp?product=CppTest

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Reference:
http://sastools.com/b2/post/79394064

A List of Unit Testing framework can be found at
http://www.xprogramming.com/software.htm