Add function reference support for use with shouldThrow

[aerb]

As an alternative syntax to:

val theFunction = { myThrowingFunction() }

// Expect any exception
theFunction shouldThrow AnyException

It would be really nice to add function reference syntax such as:

::myThrowingFunction shouldThrow AnyException

If the function takes in an argument it would then be:

::myThrowingFunction providedWith "some argument" shouldThrow AnyException

I've hacked these implementations in my own project as:

fun <R: Throwable> KFunction0<R>.shouldThrow(expectedException: KClass<R>) {
    val f = { this }
    f.shouldThrow(expectedException)
}

infix fun <P1, R> KFunction1<P1, R>.providedWith(arg: P1): () -> Any? = {
    this.invoke(arg)
}

I would be happy to clean it up, and submit a formal PR if this sort of feature interests you.

Thanks!

[aerb]

An alternate, simpler approach could be to introduce a wrapper function that returns a lambda for use with shouldThrow.

For example:

invoking { myThrowingFunction() } shouldThrow AnyException

fun invoking(f: () -> Unit): () -> Unit = f

I guess ultimately what I'm trying to avoid is having to define a local interim variable that is then passed to shouldThrow. I think one of these two approaches would avoid some of the variable noise in tests.

[MarkusAmshove]

I really like that idea, as it reduces the noise in tests.

Can the providedWith function work with an arbitrary number of parameters? If not I would prever the second version. The second version also doesn't abstract away the function call which makes it a bit clearer what is tested. If you like, send a PR 👍