Add custom information to an assertion error message.

[evant]

This came up as a response to #12. It would be useful to add additional information to a failure to aid with tracking down the cause. Some bikeshed syntax (may change):

assertThat(success, context = { "DB state: " + repository.findUser(USER_ID) }).hasSize(1)

// expected [size]:<1> but was:<0>
//   DB state: User { name = "Tim" }"

[neeme-praks-sympower]

What's the status with this? It does not seem to be implemented in 0.25?

[evant]

Nothing yet, needs some design work. If you have usecases you'd like to share ot would be helpful.

[neeme-praks-sympower]

My usecase: the assertion is too specific, I would like to add some context to it. Sample code:

  private fun assertThatEventsStored(expectedEvents: List<Event>) {
    argumentCaptor<Event> {
      verify(eventRepository, times(expectedEvents.size)).save(capture())
      allValues.zip(expectedEvents) { actualEvent, expectedEvent ->
        assertThat(actualEvent.eventType).isEqualTo(expectedEvent.eventType)
        assertThat(actualEvent.equipmentNumber).isEqualTo(expectedEvent.equipmentNumber)
        if (expectedEvent.payload != null) {
          assertThat(actualEvent.payload).isEqualTo(expectedEvent.payload)
        }
      }

    }
    verifyNoMoreInteractions(eventRepository)
  }

Now, if equipmentNumber or payload assertion fails, I would also like to know the associated eventType (as it is a loop, line number from the exception does not help me). So I would like to add a message to the assertion failure message (the original failure message would still be there).