path: root/doc/cookbook.dox

/*! \page cppunit_cookbook CppUnit Cookbook
Here is a short cookbook to help you get started.


\section simple_test_case Simple Test Case
You want to know whether your code is working. 

How do you do it? 

There are many ways. Stepping through a debugger or 
littering your code with stream output calls are two of 
the simpler ways, but they both have drawbacks.
Stepping through your code is a good idea, but it 
is not automatic. You have to do it every time you
make changes. Streaming out text is also fine, 
but it makes code ugly and it generates far more 
information than you need most of the time.

Tests in %CppUnit can be run automatically. 
They are easy to set up and once you have 
written them, they are always there to help 
you keep confidence in the quality of your code.

To make a simple test, here is what you do:

Subclass the \link CppUnit::TestCase TestCase \endlink class. 
Override the method \link CppUnit::TestCase::runTest() runTest()\endlink. 
When you want to check a value, call 
\link CPPUNIT_ASSERT() CPPUNIT_ASSERT(bool) \endlink
and pass in an expression that is true if the 
test succeeds. 

For example, to test the equality comparison 
for a Complex number class, write:

\code
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)) );
  }
};
\endcode

That was a very simple test. Ordinarily, 
you'll have many little test cases that you'll 
want to run on the same set of objects. To do 
this, use a fixture.






\section fixture Fixture
A fixture is a known set of objects that 
serves as a base for a set of test cases. 
Fixtures come in very handy when you are 
testing as you develop. 

Let's try out this style of development and 
learn about fixtures along the away. Suppose 
that we are really developing a complex 
number class. Let's start by defining a 
empty class named Complex.

\code
class Complex {};
\endcode

Now create an instance of ComplexNumberTest 
above, compile the code and see what happens. 
The first thing we notice is a few compiler 
errors. The test uses <tt>operator ==</tt>, but it is 
not defined. Let's fix that.

\code
bool operator==( const Complex &a, const Complex &b) 
{ 
  return true; 
}
\endcode

Now compile the test, and run it. This time it 
compiles but the test fails. 
We need a bit more to get an <tt>operator ==</tt>working 
correctly, so we revisit the code.

\code
class Complex { 
  friend bool 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; 
}
\endcode

If we compile now and run our test it will pass. 

Now we are ready to add new operations and 
new tests. At this point a fixture would be 
handy. We would probably be better off when 
doing our tests if we decided to instantiate 
three or four complex numbers and reuse them 
across our tests. 

Here is how we do it:
- Add member variables for each part of the 
  \link CppUnit::TestFixture fixture \endlink
- Override \link CppUnit::TestFixture::setUp() setUp() \endlink
  to initialize the variables
- Override \link CppUnit::TestFixture::tearDown() tearDown() \endlink
  to release any permanent resources you allocated in 
  \link CppUnit::TestFixture::setUp() setUp() \endlink

\code
class ComplexNumberTest : public CppUnit::TestFixture {
private:
  Complex *m_10_1, *m_1_1, *m_11_2;
public:
  void setUp()
  {
    m_10_1 = new Complex( 10, 1 );
    m_1_1 = new Complex( 1, 1 );
    m_11_2 = new Complex( 11, 2 );  
  }

  void tearDown() 
  {
    delete m_10_1;
    delete m_1_1;
    delete m_11_2;
  }
};
\endcode

Once we have this fixture, we can add the complex 
addition test case and any others that we need 
over the course of our development.



\section test_case Test Case

How do you write and invoke individual tests using a fixture? 

There are two steps to this process:
- Write the test case as a method in the fixture class
- Create a TestCaller which runs that particular method

Here is our test case class with a few extra case methods:

\code
class ComplexNumberTest : public CppUnit::TestFixture  {
private:
  Complex *m_10_1, *m_1_1, *m_11_2;
public:
  void setUp()
  {
    m_10_1 = new Complex( 10, 1 );
    m_1_1 = new Complex( 1, 1 );
    m_11_2 = new Complex( 11, 2 );  
  }

  void tearDown() 
  {
    delete m_10_1;
    delete m_1_1;
    delete m_11_2;
  }

  void testEquality()
  {
    CPPUNIT_ASSERT( *m_10_1 == *m_10_1 );
    CPPUNIT_ASSERT( !(*m_10_1 == *m_11_2) );
  }

  void testAddition()
  {
    CPPUNIT_ASSERT( *m_10_1 + *m_1_1 == *m_11_2 );
  }
};
\endcode

One may create and run instances for each test case like this:

\code
CppUnit::TestCaller<ComplexNumberTest> test( "testEquality", 
                                             &ComplexNumberTest::testEquality );
CppUnit::TestResult result;
test.run( &result );
\endcode

The second argument to the test caller constructor is the address of 
a method on ComplexNumberTest. When the test caller is run, 
that specific method will be run.  This is not a useful thing to do, 
however, as no diagnostics will be displayed.  
One will normally use a \link ExecutingTest TestRunner \endlink (see below) 
to display the results.

Once you have several tests, organize them into a suite.





\section suite Suite

How do you set up your tests so that you can run them all at once?

%CppUnit provides a \link CppUnit::TestSuite TestSuite \endlink class 
that runs any number of TestCases together. 

We saw, above, how to run a single test case.

To create a suite of two or more tests, you do the following:

\code
CppUnit::TestSuite suite;
CppUnit::TestResult result;
suite.addTest( new CppUnit::TestCaller<ComplexNumberTest>(
                       "testEquality", 
                       &ComplexNumberTest::testEquality ) );
suite.addTest( new CppUnit::TestCaller<ComplexNumberTest>(
                       "testAddition", 
                       &ComplexNumberTest::testAddition ) );
suite.run( &result );
\endcode         

\link CppUnit::TestSuite TestSuites \endlink don't only have to 
contain callers for TestCases.  They can contain any object 
that implements the \link CppUnit::Test Test \endlink interface.
For example, you can create a 
\link CppUnit::TestSuite TestSuite \endlink in your code and
I can create one in mine, and we can run them together 
by creating a \link CppUnit::TestSuite TestSuite \endlink 
that contains both:

\code
CppUnit::TestSuite suite;
CppUnit::TestResult result;
suite.addTest( ComplexNumberTest::suite() );
suite.addTest( SurrealNumberTest::suite() );
suite.run( &result );
\endcode




\section test_runner TestRunner

How do you run your tests and collect their results?

Once you have a test suite, you'll want to run it. %CppUnit provides tools 
to define the suite to be run and to display its results. 
You make your suite accessible to a \link ExecutingTest TestRunner \endlink
program with a static method <I>suite</I> that returns a test suite.

For example, to make a ComplexNumberTest suite available to a 
\link ExecutingTest TestRunner \endlink, add the following code to 
ComplexNumberTest:

\code
public: 
  static CppUnit::TestSuite *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;
  }
\endcode

\anchor test_runner_code
To use the text version, include the header files for the tests in Main.cpp:

\code
#include <cppunit/ui/text/TestRunner.h>
#include "ExampleTestCase.h"
#include "ComplexNumberTest.h"
\endcode

And add a call to 
\link ::CppUnit::TextUi::TestRunner::addTest addTest(CppUnit::Test *) \endlink 
in the <tt>main()</tt> function:

\code
int main( int argc, char **argv)
{
  CppUnit::TextUi::TestRunner runner;
  runner.addTest( ExampleTestCase::suite() );
  runner.addTest( ComplexNumberTest::suite() );
  runner.run();
  return 0;
}
\endcode

The \link ExecutingTest TestRunner \endlink will run the tests. 
If all the tests pass, you'll get an informative message. 
If any fail, you'll 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

%CppUnit distinguishes between <I>failures</I> and <I>errors</I>. A failure is 
anticipated and checked for with assertions. Errors are unanticipated problems 
like division by zero and other exceptions thrown by the C++ runtime or your code.




\section helper_macros Helper Macros

As you might have noticed, implementing the fixture static <tt>suite()</tt> 
method is a repetitive and error prone task. A \ref WritingTestFixture set of 
macros have been created to automatically implements the 
static <tt>suite()</tt> method.

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

\code
#include <cppunit/extensions/HelperMacros.h>

class ComplexNumberTest : public CppUnit::TestFixture  {
\endcode
First, we declare the suite, passing the class name to the macro:
\code
CPPUNIT_TEST_SUITE( ComplexNumberTest );
\endcode
The suite created by the static <tt>suite()</tt> method is named after 
the class name.
Then, we declare each test case of the fixture:
\code
CPPUNIT_TEST( testEquality );
CPPUNIT_TEST( testAddition );
\endcode
Finally, we end the suite declaration:
\code
CPPUNIT_TEST_SUITE_END();
\endcode
At this point, a method with the following signature has been implemented:
\code
static CppUnit::TestSuite *suite();
\endcode
The rest of the fixture is left unchanged:
\code
private:
  Complex *m_10_1, *m_1_1, *m_11_2;
public:
  void setUp()
  {
    m_10_1 = new Complex( 10, 1 );
    m_1_1 = new Complex( 1, 1 );
    m_11_2 = new Complex( 11, 2 );  
  }

  void tearDown() 
  {
    delete m_10_1;
    delete m_1_1;
    delete m_11_2;
  }

  void testEquality()
  {
    CPPUNIT_ASSERT( *m_10_1 == *m_10_1 );
    CPPUNIT_ASSERT( !(*m_10_1 == *m_11_2) );
  }

  void testAddition()
  {
    CPPUNIT_ASSERT( *m_10_1 + *m_1_1 == *m_11_2 );
  }
};
\endcode

The name of the \link CppUnit::TestCaller TestCaller \endlink added to the
suite are a composition of the fixture name and the method name. 

In the present case, the names would be:
"ComplexNumberTest.testEquality" and "ComplexNumberTest.testAddition".

The \link WritingTestFixture helper macros \endlink help you write comon assertion.
For example, to check that ComplexNumber throws a MathException when dividing
a number by 0:
- add the test to the suite using CPPUNIT_TEST_EXCEPTION, specifying the expected
  exception type.
- write the test case method

\code
CPPUNIT_TEST_SUITE( ComplexNumberTest );
// [...]
CPPUNIT_TEST_EXCEPTION( testDivideByZeroThrows, MathException );
CPPUNIT_TEST_SUITE_END();

// [...]

  void testDivideByZeroThrows()
  {
    // The following line should throw a MathException.
    *m_10_1 / ComplexNumber(0);
  }
\endcode

If the expected exception is not thrown, then a assertion failure is reported.




\section test_factory_registry TestFactoryRegistry

The TestFactoryRegistry was created to solve two pitfalls:
- forgetting to add your fixture suite to the test runner (since it is in 
  another file, it is easy to forget)
- compilation bottleneck caused by the inclusion of all test case headers 
  (see \ref test_runner_code "previous example")

The TestFactoryRegistry is a place where suites can be registered at initialization
time.

To register the ComplexNumber suite, in the .cpp file, you add:

\code
#include <cppunit/extensions/HelperMacros.h>

CPPUNIT_TEST_SUITE_REGISTRATION( ComplexNumberTest );
\endcode

Behind the scene, a static variable type of 
\link CppUnit::AutoRegisterSuite AutoRegisterSuite \endlink is declared.
On construction, it will 
\link CppUnit::TestFactoryRegistry::registerFactory(TestFactory*) register \endlink 
a \link CppUnit::TestSuiteFactory TestSuiteFactory \endlink into the 
\link CppUnit::TestFactoryRegistry TestFactoryRegistry \endlink. 
The \link CppUnit::TestSuiteFactory TestSuiteFactory \endlink returns
the \link CppUnit::TestSuite TestSuite \endlink returned by ComplexNumber::suite().

To run the tests, using the text test runner, we don't need to include the fixture
anymore:

\code
#include <cppunit/extensions/TestFactoryRegistry.h>
#include <cppunit/ui/text/TestRunner.h>

int main( int argc, char **argv)
{
  CppUnit::TextUi::TestRunner runner;
\endcode
First, we retreive the instance of the 
\link CppUnit::TestFactoryRegistry TestFactoryRegistry \endlink:
\code
  CppUnit::TestFactoryRegistry &registry = CppUnit::TestFactoryRegistry::getRegistry();
\endcode
Then, we obtain and add a new \link CppUnit::TestSuite TestSuite \endlink created 
by the  \link CppUnit::TestFactoryRegistry TestFactoryRegistry \endlink that 
contains all the test suite registered using CPPUNIT_TEST_SUITE_REGISTRATION().
\code
  runner.addTest( registry.makeTest() );
  runner.run();
  return 0;
}
\endcode




\section post_build_check Post-build check

Well, now that we have our unit tests running, how about integrating unit 
testing to our build process ?

To do that, the application must returns a value different than 0 to indicate that
there was an error.

\link CppUnit::TextUi::TestRunner::run() TestRunner::run() \endlink returns 
a boolean indicating if the run was successful.

Updating our main programm, we obtain:
\code
#include <cppunit/extensions/TestFactoryRegistry.h>
#include <cppunit/ui/text/TestRunner.h>

int main( int argc, char **argv)
{
  CppUnit::TextUi::TestRunner runner;
  CppUnit::TestFactoryRegistry &registry = CppUnit::TestFactoryRegistry::getRegistry();
  runner.addTest( registry.makeTest() );
  bool wasSuccessful = runner.run( "", false );
  return !wasSuccessful;
}
\endcode

Now, you need to run your application after compilation.

With Visual C++, this is done in <em>Project Settings/Post-Build step</em>, 
by adding the following command: <tt>"$(TargetPath)"</tt>. It is expanded to 
the application executable path. Look up the project 
<tt>examples/cppunittest/CppUnitTestMain.vcproj</tt> which
use that technic.



Original version by Michael Feathers.
Doxygen conversion and update by Baptiste Lepilleur.
*/