How I do C++ Testing

My presentation about how I do C++ testing at Agile Aragón Testing Lab.

Transcript

1. C++ Testing (how I do it) Testing Lab (Agile Aragón) March 9, 2013 Zaragoza - Spain David Alfonso @davidag
2. C++ compiled, multi-paradigm, static typing, high- performance apps,...
3. Types of tests Unit Tests, Integration Tests, Usability Tests (not many), Performance Tests,...
4. Open Source Tools Continuous Integration (BuildBot) xUnit Framework (Google Test & Mock) Static Analysis (cppcheck) Dynamic Analysis (valgrind) VCS (CVS & Git)
5. xUnit Frameworks ...a lot to choose from... Boost Test Library UnitTest++ CppUnit CppUnitLite
6. Google Test + Google Mock open source, multiplatform, easy to start with, powerful,...
7. Google Test state-based testing SUT
8. TEST(StackTest, IsEmptyInitially) { Stack s; ASSERT_EQ(0, s.size()); } TEST(StackTest, PushWorks) { Stack s; s.push(5); ASSERT_EQ(1, s.size()); } Test case
9. Google Mock interaction-based testing SUT A' B'
10. // SUT = Race TurtleMock turtle; EXPECT_CALL(turtle, Move(Gt(0))) .Times(AtLeast(1)) .WillOnce(Return(true)) .WillRepeatedly(Return(false) ); Race race(turtle); race.runOneStep();
11. // SUT = Race TurtleMock turtle; EXPECT_CALL(turtle, Move(Gt(0))) .Times(AtLeast(1)) .WillOnce(Return(true)) .WillRepeatedly(Return(false) ); Race race(turtle); race.runOneStep(); EXPECT_CALL(mock_obj, method(matchers)) .Times(cardinality) .WillOnce(action) .WillRepeatedly(action);
12. Techniques to put tests in place
13. New code Aim: Testable code SOLID & GRASP principles, design patterns, TDD, etc.
14. Dependency Injection programming against abstractions
15. // Constructor DI class Data { public: bool empty() = 0; int count() = 0; }; class ConcreteData : public Data {...}; class FakeData : public Data {...}; class Processor { public: Processor(Data* data); };
16. // Setter DI class Data { public: bool empty() = 0; int count() = 0; }; class ConcreteData : public Data {...}; class FakeData : public Data {...}; class Processor { public: Processor(); void SetData(Data* data) { d_ = d; }
17. // Template DI template <typename T> class Processor { public: Processor(); private: T data_; }; // Production code Processor<ConcreteData> p; // Testing code Processor<FakeData> p;
18. Legacy code characterization tests, not too strict about FIRST principles of unit testing, I prefer to have classes in test harnesses
19. Decoupling dependencies using preprocessing and linking stages Legacy Code
20. // Preprocessing // DbRecord.cpp #include "DbRecord.h" #include "DbDefs.h" ... Mysql::connect(host); ... Legacy Code #ifdef TESTING Mysql::connect() {} #else #include "Mysql.h" #endif
21. // Preprocessing // DbRecord.cpp #include "Pre.h" #include "DbRecord.h" ... // DbRecordTests.cpp #include "Pre.h" #include "DbRecord.h" class MysqlStub { ... }; ... // Pre.h -> Different in tests // than in production code #define Mysql MysqlStub Legacy Code
22. // Linking // BFake.cpp class B { ... }; // ATests.cpp #include "A.h" // It will include "B.h" TEST(...) { } // Compile BFake.cpp instead of B.cpp Legacy Code
23. Accessing private methods and variables Sometimes you don't have a choice... Legacy Code
25. // Option 1: Review your design!!!
26. // Option 1: Review your design!!! // Option 2: Getters class A { public: const Obj& getObject() const { return obj; } private: Obj obj; };
27. // Option 1: Review your design!!! // Option 2: Getters // Option 3: Add testing functions class A { public: ... bool DoSomeCheckUsingPrivateStuff(); private: ... };
28. // Option 1: Review your design!!! // Option 2: Getters // Option 3: Add testing functions // Option 4: Make some friends :) class MyClass { private: // Google Test macro FRIEND_TEST(MyClassTest, MyMethod); };
29. // Option 1: Review your design!!! // Option 2: Getters // Option 3: Add testing functions // Option 4: Make some friends :) // Option 5: Redefine private/protected // MyClassTests.cpp #define private public #include "MyClass.h" MyClass my_class; my_class.private_method();
30. Thank you :)