Effective testing strategies to raise code quality

Transcript

1. Test Doubles & Test Data (First class citizens for writing unit test) By MURALIDHARAN KATHIRESAN
2. Quality Agility Early bug discovery Better Understanding Courage to refactor And improved productivity Why to Test the code?
3. What makes code hard to test ? Let’s review some anti-patterns, code smells, and bad practices that we should avoid when writing testable code
5. What makes a Good Unit Test ? Perform the bare minimum of work required to achieve its goal Be easy to understand Be easy to maintain Execute in a shorter period of time A descriptive test name Narrow and Focused
6. Unit Testing Best Practices examples
7. Continued.. One assert per test method Avoid test interdependence Keep it short, sweet and visible Recognize test setup pain as a smell Add unit tests to Continuous integration build
8. What we follow in News? JSON Parsing Tests Snapshot Tests ViewState Tests Presenter Tests UseCase Tests
9. A test double is an object that can stand in for a real object in a test, similar to how a stunt double stands in for an actor in a movie. These are sometimes all commonly referred to as “mocks”, but it's important to distinguish between the different types of test doubles since they all have different uses. Test Doubles
10. Dummy A dummy implementation is an object which is not used in our test. Basically, we merely use it to let compile the test.
11. Stub A Stub is a dummy that returns a specific value because the rest of the system relying on this specific value to continue running in a test. A stub has no logic, and only returns what we tell it to return
12. Spy A Spy dependency is a more powerful version of the Stub one. It provides information based on how its methods are called—like the parameters values and the exact order methods are called
13. Mock A mock is similar to a spy and does a little more. It also tests behavior by having the assertion go into the mock itself
14. Test Input sources sources Local JSON Test Data Local object instances
15. It can be called like: User.testData(userName: “Murali”) Test Data
16. testData() is a static function that create an object Only one testData() for type testData() can create an object passing no arguments as all its property have default values default values reuse existing testData() whatever is possible default values use nil when the property is optional Benefits of Test Data?
17. Credits Special thanks to ￮ Aaina vivek jain ￮ Giuseppe basile who introduced me the concept of test doubles and helped me to write quality code!
18. Thanks! Any questions? You can find me at ￮ @https://twitter.com/muralidharan_k
19. https://medium.com/@gbasile/efficient-test-data-creation-in-swift-822fc14fef27 https://martinfowler.com/bliki/TestDouble.html https://www.toptal.com/qa/how-to-write-testable-code-and-why-it-matters https://clean-swift.com/swifty-little-mocker/ References