Suggestion: Support for multiple expectations per test

[wldmr]

Being a fan of simple libraries, I was drawn to yours. Great work!

However, when I found myself wanting to check the contents of a HashMap, I found it difficult to compose expectations (which is a general problem with fluent assertions, it seems).

So I came up with this: There's a container for multiple expectation chains. You gradually add them, and at the end you call conclude_*() as you would on a single chain.

For a HashMap of Bitflags (my usecase) this would look something like

start_expectations()
    .and(expect!(&flags["f1"]).to_contain(Call))
    .and(expect!(&flags["f2"]).to_contain(Call))
    .and(expect!(&flags["a"]).not().to_contain(Call))
    .and(expect!(&flags["b"]).not().to_contain(Call))
    .and(expect!(&flags["c"]).not().to_contain(Call))
    .and(
        expect!(&flags["other"])
            .soft()
            .not()
            .to_contain(Definition)
            .to_contain(Usage)
            .and()
            .to_intersect(Temp | Global),
    )
    .conclude_panic();

There's also a way to modify multiple expectations non-fluently. The above checks would then look something like this:

checks.here(expect!(&flags["f1"]).to_contain(Call));
checks.here(expect!(&flags["f2"]).to_contain(Call));
checks.here(expect!(&flags["a"]).not().to_contain(Call));
checks.here(expect!(&flags["b"]).not().to_contain(Call));
checks.here(expect!(&flags["c"]).not().to_contain(Call));

checks.here(
    expect!(&flags["other"])
        .soft()
        .not()
        .to_contain(Definition)
        .to_contain(Usage)
        .and()
        .to_intersect(Temp | Global),
);

checks.conclude_panic();

This is mainly meant for cases where you want to ensure certain intermediate results before the "big one" at the end.

What do you think? Would composition be something you'd find useful for this library? I'm happy to discuss and tweak things, of course. But I thought I'd start with a concrete suggestion and not just by opening an issue with a vague request.