This document describes very shortly how to install the [http://sourceforge.net/projects/cppunit/ CppUnit] framework under Unix and how to write and run a very simplistic test case. This should get you started with using CppUnit, so that you can follow and try out the examples given in the [http://cppunit.sourceforge.net/doc/lastest/cppunit_cookbook.html CppUnit CookBook].

Installing

Download the latest version of CppUnit from http://downloads.sourceforge.net/cppunit/cppunit-1.12.1.tar.gz.

Let us install it under /var/tmp/cppunit/install:

$ cd /var/tmp/
$ mv ~/cppunit-1.12.1.tar.gz .
$ tar xzf cppunit-1.12.1.tar.gz
$ ln -s cppunit-1.12.1 cppunit
$ cd cppunit
$ ./configure --prefix=`pwd`/install
$ make
$ make check
$ make install

Writing a simplistic test case

Suppose we are developing a class Complex for dealing with complex numbers. In the following code, the operator+ intentionally contains a bug:

// files Complex.h/Complex.cpp

class Complex { 
  friend bool   operator==(const Complex& a, const Complex& b);
  friend Complex operator+(const Complex& a, const Complex& b);
  double real, imaginary;
public:
  Complex( double r, double i = 0 )  : real(r), imaginary(i) {}
};

bool operator==( const Complex &a, const Complex &b )
{ 
  return a.real == b.real  &&  a.imaginary == b.imaginary; 
}

Complex operator+( const Complex &a, const Complex &b )
{ 
  // BUG! imaginary part should be 'a.imaginary + b.imaginary'
  return Complex(a.real + b.real, a.imaginary + b.real); 
}

Now let us write a CppUnit test case for this class:

// file ComplexNumberTest.h/.cpp

#include <cppunit/TestCase.h>
#include "Complex.h"

class ComplexNumberTest : public CppUnit::TestCase { 
public: 
  ComplexNumberTest( std::string name ) : CppUnit::TestCase( name ) {}
  
  void runTest() {
    CPPUNIT_ASSERT( Complex (10, 1) == Complex (10, 1) );
    CPPUNIT_ASSERT( !(Complex (1, 1) == Complex (2, 2)) );
    CPPUNIT_ASSERT( Complex (1, 2) + Complex(3, 4) == Complex (4, 6));
  }
};

// file runComplexNumberTest.cpp

#include "ComplexNumberTest.h"

int main()
{
  ComplexNumberTest myTest("My first CppUnit test");
  
  myTest.runTest();
}

For this, we have to subclass the TestCase class and to override the method runTest(). To check a value, we call CPPUNIT_ASSERT(bool) and pass in an expression that is true if the test succeeds.

Compiling and running

Suppose we put all the above code into one file ComplexNumberTest.cpp. Then the following makefile will do the job for us:

INCLS   = -I/var/tmp/cppunit/install/include/
LIBDIRS = -L/var/tmp/cppunit/install/lib
LIBS    = -lcppunit -ldl # note that CppUnit needs libld.so!

# Implicit rule: How to make an executable from a .cpp-file
%: %.cpp
        ${CC} -o $@ $< ${CXXFLAGS} ${INCLS} ${LIBDIRS} ${LIBS}

runtest: runComplexNumberTest
        export LD_LIBRARY_PATH=/var/tmp/cppunit/install/lib && ./runComplexNumberTest

Note that CppUnit needs the library ld.so in the linking step.

Now we can compile and run the program:

$ make runtest
cc -o ComplexNumberTest ComplexNumberTest.cpp  -I/var/tmp/cppunit/install/include/ -L/var/tmp/cppunit/install/lib -lcppunit -ldl
export LD_LIBRARY_PATH=/var/tmp/cppunit/install/lib && ./ComplexNumberTest
terminate called after throwing an instance of 'CppUnit::Exception'
  what():  assertion failed
- Expression: Complex (1, 2) + Complex(3, 4) == Complex (4, 6)

/bin/sh: line 1:  1457 Aborted                 ./ComplexNumberTest

As we can see, the third assertion failed, which detects the bug in our operator+.

Fixtures, Callers, Suites, and Runners

Now go on and read the rest of the [http://cppunit.sourceforge.net/doc/lastest/cppunit_cookbook.html CppUnit CookBook] and try out the examples given there. You will learn about TestFixtures, TestCallers, TestSuites, and TestRunners.

In short:

• A TestFixture is a set of objects that serves as a base for a set of test cases, together with methods that implement these test cases.

• A TestCaller runs a particular method (test case) of a fixture.

• A TestSuite runs any number of callers together.

• A TestRunner runs a suite and displays its results.

Here is a complete program:

// files ComplexNumberTestSuite.h/.cpp

// A test suite for Complex, run by a runner

#include <cppunit/TestFixture.h>
#include <cppunit/TestSuite.h>
#include <cppunit/TestCaller.h>

class ComplexNumberTest : public CppUnit::TestFixture  {
private:
  Complex *a, *b, *s;
public:
  void setUp()
  {
    a = new Complex( 1, 2 );
    b = new Complex( 3, 4 );
    s = new Complex( 4, 6 );  
  }

  void tearDown() 
  {
    delete a;
    delete b;
    delete s;
  }

  void testEquality()
  {
    CPPUNIT_ASSERT( *a == *a );
    CPPUNIT_ASSERT( !(*a == *b) );
  }

  void testAddition()
  {
    CPPUNIT_ASSERT( *a + *b == *s );
  }

  static CppUnit::Test *suite()
  {
    CppUnit::TestSuite *suiteOfTests = new CppUnit::TestSuite( "ComplexNumberTest" );

    suiteOfTests->addTest( new CppUnit::TestCaller<ComplexNumberTest>( 
                                   "testEquality", 
                                   &ComplexNumberTest::testEquality ) );
    suiteOfTests->addTest( new CppUnit::TestCaller<ComplexNumberTest>(
                                   "testAddition",
                                   &ComplexNumberTest::testAddition ) );
    return suiteOfTests;
  }
};

// file runTestSuite.cpp

#include <cppunit/ui/text/TestRunner.h>
#include "ComplexNumberTestSuite.h"

int main()
{
  CppUnit::TextUi::TestRunner runner;
  runner.addTest( ComplexNumberTest::suite() );
  //runner.addTest( AnotherTestFixture::suite() );
  //runner.addTest( AnExampleTestCase::suite() );
  runner.run();
}

The TestRunner will run the tests. If all the tests pass, we shall get an informative message. If any fail, we shall get the following information:

• The name of the test case that failed
• The name of the source file that contains the test
• The line number where the failure occurred

• All of the text inside the call to CPPUNIT_ASSERT() which detected the failure

The output of the above program is

..F


!!!FAILURES!!!
Test Results:
Run:  2   Failures: 1   Errors: 0


1) test: testAddition (F) line: 56 ComplexNumberTestSuite.cpp
assertion failed
- Expression: *a + *b == *s

Helper macros

Implementing the static suite() method in a TestFixture is a repetitive and error prone task. A set of macros have been created to automatically implement this method.

The following code is a rewrite of ComplexNumberTest using these macros:

// file ComplexNumberTestWithMacro.h/.cpp

#include <cppunit/extensions/HelperMacros.h>

class ComplexNumberTestWithMacro : public CppUnit::TestFixture  {

CPPUNIT_TEST_SUITE( ComplexNumberTestWithMacro );
CPPUNIT_TEST( testEquality ); 
CPPUNIT_TEST( testAddition );
CPPUNIT_TEST_SUITE_END(); 

// remainder as in the class above

private:
  Complex *a, *b, *s;
public:
  void setUp()
  {
    a = new Complex( 1, 2 );
    b = new Complex( 3, 4 );
    s = new Complex( 4, 6 );  
  }

  void tearDown() 
  {
    delete a;
    delete b;
    delete s;
  }

  void testEquality()
  {
    CPPUNIT_ASSERT( *a == *a );
    CPPUNIT_ASSERT( !(*a == *b) );
  }

  void testAddition()
  {
    CPPUNIT_ASSERT( *a + *b == *s );
  }
};

There are other helper macros, for example, to check that a specific exception is thrown under specific circumstances. Check the documentation.