Parameterized Tests

This is a form of Data-Driven testing. The “Act” step is the same for all the tests, but the Arrange and Assert parts are parameterized.

Session Outline

• 5 min connect: Automated tests that are cheap to maintain (take a guess)
• 5 min concept: Parameterized Tests
• 40 min do: Refactor to parameterized
• 5 min reflect: Reliability and Maintainability

Connect:

Read the list of topics below. Add an upvote to those that increase your chances of achieving “Automated unit tests that are cheap to maintain” and add a downvote to those which reduce your chances. Irrelevant topics should be left blank.

• Test Fixture
• Travelling Salesman
• Artificial Intelligence
• Arrange - Act - Assert
• Code Coverage
• Duplicated test code
• Continuous Integration
• Mocks
• Liskov Substitution Principle
• Image diffs
• Genetic Algorithms
• Custom assertions

Concept: Parameterized Tests

Find the documentation for parameterized tests in the test tool and programming language your group is using. Ask them to read it and each person to make their own mind-map with these starting nodes:

• Center node: Parameterized Tests
• Why?
• When?
• How?

Do: Write some parameterized tests

Create some tests with a lot of duplication for a kata like Mars Rover. One of the tests should be failing (you have included an obvious bug). Ask them to fix the bug then refactor the tests to reduce duplication by using a parameterized test.

When they have it working, ask them to re-insert the bug so one of the cases fails. Show that they still get only one test failure and the message is intelligable.

Reflect: Reliability and Maintainability

What have you learnt about parameterized testing? When is it a good idea? How does it affect test Maintainability and Reliability? Add some notes to your mindmap and keep it next to your computer.