Test a behaviour

A test proves one behaviour. Name that behaviour before you write the test. Then pick the shape below that fits it.

Each shape returns a fixed, independent answer. A test that reruns the code under test cannot catch its mistakes. Read tests that earn their place first.

1. A domain rule: a property

A rule that holds for many inputs is an it.prop over Effect Arbitrary inputs. Use it.effect.prop when the check returns an Effect.

The core suite generates names and checks their length after trimming. The assertion states the accepted length without calling the validator:

Read property-based testing.

2. Anything with history: a model