Strategy - Slice

For when ‘Peel’ strategy doesn’t work, like when the difficult-to-test code is in the middle of the testable code, not at the beginning or end.

Learning Goals

• Explain when to use the ‘slice’ strategy to break dependencies in difficult to test code
• Use the ‘slice’ strategy to extract testable functions from legacy code that is suitable for it.

Session Outline

• 5 min connect: identify testability problems
• 10 min concept: Slice
• 40 min do Slice on a function
• 5 min reflect: When to Slice

Connect - identify testability problems

Copy a symbol next to the items on this list which might make a function difficult to test:

• Function is void ie no return value
• Function name is more than 20 characters
• Function has only one statement
• Function gives different return values for same input parameters
• Function has an empty parameter list
• Function contains log statements using printf
• Function is called from many places in the system

This is a Pick only the correct items connect.

Concept: Slice

This picture visualizes the Slice strategy:

The function you’re trying to test has a line that is difficult to test in the middle. You can’t easily use Peel to remove it. You need to slice away the depencency and replace the hard to test call with a call to a stub or a fake.

Concrete: Slice

One way to solve TirePressure is using Slice. You can also do it on ‘getScoreboard’ in IceCreamScores

Reflect - when to Peel, when to Slice

When should you use ‘slice’ rather than ‘peel’? Are there any disadvantages to using it?