Testing

Contract Tests are examples that describe the behaviour of an abstraction by expressing what cannot be encoded in the type system. These are typically helpful in testing adapters as defined in the Ports & Adapters architecture.

A collaboration test is an example of interactions between the subject of the test and its collaborators often replaced with test doubles. A contract test confirms assumptions made in test doubles.

A function is one of the smallest units of behaviour. Functions can be composed to build coarser behaviours. What granularity and altitude to test behaviours on?