func TestProcessor(t *testing.T) { evensFilter := func(d stream.T, emitter stream.Emitter) { if d.(int)%2 == 0 { emitter.Emit(d) } } Convey("Given I have a context", t, func() { context := rivers.NewContext() Convey("And a stream of data", func() { in, out := stream.New(2) out <- 1 out <- 2 close(out) Convey("When I apply the transformer to the stream", func() { transformer := transformers.OnData(evensFilter) transformer.Attach(context) transformed := transformer.Transform(in) Convey("Then a transformed stream is returned", func() { So(transformed.ReadAll(), ShouldResemble, []stream.T{2}) }) }) Convey("When I close the context", func() { context.Close(stream.Done) Convey("And I apply the transformer to the stream", func() { transformer := transformers.OnData(evensFilter) transformer.Attach(context) next := transformer.Transform(in) Convey("Then no item is sent to the next stage", func() { So(next.ReadAll(), ShouldBeEmpty) }) }) }) }) }) }
func (pipeline *Pipeline) OnData(fn stream.OnDataFn) *Pipeline { return pipeline.ApplyParallel(transformers.OnData(fn)) }