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ScalaTest Matchers vs MustMatchers difference

It seems for latest version of ScalaTest we have two matchers one isMatchers (ShouldMatchers before) andMustMatchers.

What's the real difference between this two? Is that kind of style the team can choose or?

Also, any difference betweenshouldBe and should be

Solution

  • The only difference is the word - quoting from the ScalaDocs for MustMatcher:

    Trait MustMatchers is an alternative to Matchers that provides the exact same meaning, syntax, and behavior as Matchers, but uses the verb must instead of should. The two traits differ only in the English semantics of the verb: should is informal, making the code feel like conversation between the writer and the reader; must is more formal, making the code feel more like a written specification.

    As for should be vs. shouldBe ... it depends on which instance of should[Be] you are invoking. In all cases shouldBe does one less registration step (because it skips the work that be does). Sometimes it looks like that means fewer objects are allocated - other times, the same steps are taken, but both "should" and "be" are registered in one pass. As far as I can tell there is no difference in behavior (at least in the day-to-day of writing tests), it's just which one you prefer stylistically.