Git diff style error logging for tests

[adrianbukros]

The PointFree folks implemented a Git diff style error logging in their test framework. It helps with identifying the difference between the expected and the actual output. Example:

State change does not match expectation: …

      AppState(
              // ...
            description: "",
    −       id: 00000000-0000-0000-0000-000000000001,
    +       id: 00000000-0000-0000-0000-000000000002,
            isComplete: false
          ),
        ]
      )

[gyulavoros]

For reference please take a look at:

• the PointFree implementation
• a conceptually similar attempt in Kotlin to pretty-print data classes