设计原则与模式: 案例介绍--CppUnit
CppUnit 是一个单元测试框架, 我们看一看它的设计是如何遵循基础的设计原则和模式的
单一职责原则TestRunner 和 TestResult 的分离
class CPPUNIT_API TestRunner {
virtual void addTest( Test *test );
virtual void run( TestResult &result, const std::string &testPath = "" );
...
};
TestRunner 负责收集并运行测试用例, 但并不主动打印测试结果. 测试结果被收集在 TestResult 对象中, 可以以各种形式被处理:
CPPUNIT_NS::TestResult controller;
CPPUNIT_NS::TestResultCollector result;
controller.addListener( &result );
...
runner.run( controller );
// Print test in a compiler compatible format.
CPPUNIT_NS::CompilerOutputter compiler_outputter( &result, CPPUNIT_NS::stdCOut() );
compiler_outputter.write();
// Print test in XML format.
CPPUNIT_NS::XmlOutputter xml_outputter( &result, CPPUNIT_NS::stdCOut() );
xml_outputter.write();
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开放封闭原则遵循开放封闭原则的一个重要特征就是 "针对接口/基类编程", 任何根据 typeid 等类型信息进行的分支处理如 if/else, switch/case 等都可以看做是破坏开放封闭原则的前兆
TestResult 对于如何处理测试过程中发生的事件是开放的, 可以通过 TestListener 来扩展
class CPPUNIT_API TestResult : protected SynchronizedObject {
virtual void addListener( TestListener *listener );
virtual void removeListener( TestListener *listener );
/// Informs TestListener that a test will be started.
virtual void startTest( Test *test );
...
};
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void TestResult::startTest( Test *test ) {
...
for ( TestListeners::iterator it = m_listeners.begin(); it != m_listeners.end(); ++it )
(*it)->startTest( test );
}
};
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voidBriefTestProgressListener::startTest( Test *test ) {
stdCOut() << test->getName();
stdCOut().flush();
m_lastTestFailed = false;
void TextTestProgressListener::startTest( Test *test ){
stdCOut() << ".";
}
接口分离原则class CPPUNIT_API Test {
virtual void run( TestResult *result ) =0;
void TestRunner::addTest( Test *test ) {
m_suite->addTest( test );
}
void TestRunner::run( TestResult &controller, const std::string &testPath ) {
TestPath path = m_suite->resolveTestPath( testPath );
Test *testToRun = path.getChildTest();
controller.runTest( testToRun );
virtual void setUp() {};
virtual void tearDown() {};
};
class CPPUNIT_API TestCase : public Test, public TestFixture {
};
int main( int argc, char* argv[] ) {
// Add the top suite to the test runner
CPPUNIT_NS::TestRunner runner;
runner.addTest( CPPUNIT_NS::TestFactoryRegistry::getRegistry().makeTest() );
runner.run( controller );
...
TestSuite *suite = new TestSuite( m_name );
addTestToSuite( suite );
return suite;
}
class CPPUNIT_API TestComposite : public Test {
...
class CPPUNIT_API TestSuite : public TestComposite {
void addTest( Test *test );
};
客户代码参见前面的 main 函数
class CPPUNIT_API TestDecorator : public Test {
...
};
class CPPUNIT_API RepeatedTest : public TestDecorator {
RepeatedTest( Test *test, int timesRepeat ) : TestDecorator( test ), m_timesRepeat(timesRepeat) {
}
void run( TestResult *result ) {
for ( int n = 0; n < m_timesRepeat; n++ ){
TestDecorator::run( result );
}
}
...
};
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2. 如何确保 TestCase 的隔离性, 即使出现异常也不影响后续 TestCase 的运行 ?
ProtectedFunctor -> Functor -> 函数指针
class TestCaseMethodFunctor : public Functor {
typedef void (TestCase::*Method)();
TestCaseMethodFunctor( TestCase *target, Method method ) : m_target( target ), m_method( method ) {
}
bool operator()() const {
(m_target->*m_method)();
return true;
}
...
bool DefaultProtector::protect( const Functor &functor, const ProtectorContext &context ) {
try {
return functor();
} catch ( Exception &failure ) {
reportFailure( context, failure );
} catch ( std::exception &e ) {
reportError( context,Message("uncaught exception of type ", e.what() ) );
} catch ( ... ) {
reportError( context, Message( "uncaught exception of unknown type") );
}
return false;
}
练习: 这里使用了 Decorator 模式的思想, 但并不是严格的 Decorator 模式, 为什么?
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Observer 模式TestResult 与 TestListener
void TestResult::addListener( TestListener *listener ) {
m_listeners.push_back( listener );
}
void TestResult::removeListener ( TestListener *listener ) {
removeFromSequence( m_listeners, listener );
}
void TestResult::startTestRun( Test *test ) {
for ( TestListeners::iterator it = m_listeners.begin(); it != m_listeners.end(); ++it )
(*it)->startTestRun( test, this );
}
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void TestResult::endTestRun( Test *test ) {
for ( TestListeners::iterator it = m_listeners.begin(); it != m_listeners.end(); ++it )
(*it)->endTestRun( test, this );
}
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Factory Method 模式调用测试用例注册表来产生测试用例
class CPPUNIT_API TestFactoryRegistry : public TestFactory {
virtual Test *makeTest();
};
Strategy 模式不同的格式的输出, 如Compiler风格的, Xml格式的, 等等
class CPPUNIT_API TextTestRunner : public CPPUNIT_NS::TestRunner {
void setOutputter( Outputter *outputter ) {
delete m_outputter;
m_outputter = outputter;
}
voidprintResult( bool doPrintResult ) {
m_outputter->write();
};
CPPUNIT_NS::TextTestRunner runner;
CPPUNIT_NS::CompilerOutputter compiler_outputter( ... );
runner.setOutputter(compiler_outputter);
Template Method 模式TestFixture 的 setUp 与 tearDown
class CPPUNIT_API TestFixture {
virtual void setUp() {};
virtual void tearDown() {};
};
void TestCase::run( TestResult *result ) {
result->startTest(this);
if ( result->protect( TestCaseMethodFunctor( this, &TestCase::setUp ), this, "setUp() failed" ) ) {
result->protect( TestCaseMethodFunctor( this, &TestCase::runTest ), this );
}
result->protect( TestCaseMethodFunctor( this, &TestCase::tearDown ), this, "tearDown() failed" );
result->endTest( this );
}
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练习: CppUnit 支持将测试结果输出到控制台, 或者文件, 但缺省并不支持同时输出到控制台和文件, 如何在遵循各种设计原则的情况下, 为 CppUnit 添加此功能?
