Allow projectors to be tested directly

[slashdotdash]

Make it possible to test a projector by directly calling a function on the projector module, passing an Ecto.Multi struct, an event, and its metadata.

Examples

Test a projector by projecting a single event:

{:ok, _changes} =
  Ecto.Multi.new()
  |> MyApp.ExampleProjector.project(event, metadata)
  |> MyApp.Repo.transaction()

Test a projector by reducing a list of events:

multi = 
  Enum.reduce(events, Ecto.Multi.new(), fn event, multi ->
    MyApp.ExampleProjector.project(multi, event, metadata)
  end)

{:ok, _changes} = MyApp.Repo.transaction(multi)