func TestReducer(t *testing.T) {
sum := func(acc, next stream.T) stream.T { return acc.(int) + next.(int) }
Convey("Given I have a context", t, func() {
context := rivers.NewContext()
Convey("And a stream of data", func() {
in, out := stream.New(3)
out <- 1
out <- 2
out <- 3
close(out)
Convey("When I apply a mapper transformer to the stream", func() {
transformer := transformers.Reduce(0, sum)
transformer.Attach(context)
next := transformer.Transform(in)
Convey("Then a transformed stream is returned", func() {
So(next.ReadAll(), ShouldResemble, []stream.T{6})
})
})
Convey("When I close the context", func() {
context.Close(stream.Done)
Convey("And I apply the transformer to the stream", func() {
transformer := transformers.Reduce(0, sum)
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) Reduce(acc stream.T, fn stream.ReduceFn) *Pipeline {
return pipeline.Apply(transformers.Reduce(acc, fn))
}