Writing unit tests has a purpose, and the purpose is NOT only to make the building Green. If you want a green build, just return true in your tests and move on. Otherwise, there are several principles you have to follow when you are writing unit tests for your project.
Generally, A unit test should satisfy the AAA Pattern: Arrange, Act, Assert. That’s at the macro level.
We’ll dig a little bit deeper inside, and give you some strong principles that will make your Unit Tests better.
Test Agenda – The key to successful Unit Testing
- Make your tests Trustworthy
- Create Maintainable tests
- Create Readable tests
Avoid Test Logic
- Use no loops: if/switch/ for/ while etc.
- A Test should only include creating, configuring, act and asserting actions
- Remember: Logic in tests leads to test bug
Enforce Test Isolation
- No dependency between tests
- Do not run a test from another test
- Run alone or all together in any order
Create Readable Tests
- Consistent structure
- No magic values
- Naming a Unit Test correctly
- Separate the Assert from action
Naming a Unit Test
- Specify what is the test scenario
- Specify what is the expected behavior return value
For example:
Add_LessThanZero_Throws_Exception
Avoid Multiple Asserts
- It’s like having multiple tests
- If one assert fails – all the rest will fail
- The test will be hard to name
- Can lead to more debugging work
Removing/Changing Tests
- Do not change or remove tests, always add new ones
- Unless:
- It is for clarity (the functionality remains the same)
- The test is not needed
- The test is needed to run differently
Do not repeat Production code
For example:
char user[] = “a”;
char password[] = “b”;
char someResult[] = UnderTest.CreateMessage(user, password);
Assert::AreEqual(user + “,” + password == someResult);
Create maintainable tests
- Avoid testing private/protected members
- Re-use code test
- Test one thing: One mock per test, avoid multiple asserts
Recap: use these best practices for successful C++ unit testing.
