add .contains() support to expectThrows{}

[kenyee]

Sometimes you want to compare that the exception message is what you expect.

I currently use a combo of assertThrows like this:

val exception = assertThrows {}
expectThat(exception.message!!).contains("somestring")

because expectThrows doesn't let me check the message..

[AlexanderGH]

This works for me in the current version:

expectThrows<Throwable> { }.get { message }.isNotNull().contains("somestring")

as does:

expectThrows<Throwable> { }.assert("message") {
    expectThat(it.message).isNotNull().contains("somestring")
}

[kenyee]

Thanks! That did work out well. An example probably should be added to the docs.
expectThrows { }.message().isNotNull().contains("...")
would be slightly nicer...

[AlexanderGH]

You could add an extension method that aliases message() to get { message }.