[RFC] HaveEach matcher

[thediveo]

In the hope that I didn't overlooked this functionality in the existing matchers: I would like to propose an Each matcher that checks that all elements of an array or slice match the specified value/matcher. Similar for maps, Each checks that all map values match the specified value/matcher.

Expect(m).To(Each(Equal(42))) // map[string]int
Expect(m).To(Each(Each(Equal(42))) // map[string][]int

border case: Expect([]string{}).To(Each(Equal(""))) is expected to succeed. If not desired, use this idiom:

Expect([]string{}).To(And(Not(BeEmpty()), Each(Equal(""))))

I can work on a PR if you like and after some clean-up and adding the necessary tests 😁.

P.S.: still struggling with the language semantics of Each and Every, but then Javascript used forEach(...) and not forEvery(...) 😉

[onsi]

hey @thediveo this sounds like a useful addition. How about HaveAllElements()? It's wordy but unlikely to collide and I think it reads well:

Expect(m).To(HaveAllElements(Equal(42)))

And paves the way for

Expect(m).To(HaveAnyElement(Equal(42)))

thoughts?

[thediveo]

wouldn't HaveAnyElement() be the same as ContainsElement()?

[onsi]

um... (awkward silence)... yes

[thediveo]

Pondering again on HaveAllElements() this appears to me ambiguous in the sense of "have all the following elements". Yet, you raise the import concern of name clashes with Each. What about HaveEach()? Avoids name clashes, keeps with the established Have... pattern, yet avoids the false friend of ContainsElements(). What do you think?

[onsi]

Yeah, you're right. HaveEach() works and makes sense to me.

[thediveo]

With this merged in #523 and #524 this issue is done. Thank you for discussing the idea and merging!