Add semantics for "expected failures"

Sometimes, esp. in TDD, it’s convenient to add a test that is expected to fail at first, but will be fixed to succeed (e.g. by adding an implementation in the application) later on. In contrast to config(enabled = false) these tests should be executed but be clearly marked (e.g. in yellow) in the output to document them as “TODOs”. The commit adding the implementation then typically also re-configures the test from an expected failure to a regular test that is expected to succeed.

[sksamuel]

pending = true could easily:

• imply a tag (if we want to do that?)
• add PENDING to output (and in Kotest 6 be highlighted properly)
• invert the result

[sksamuel]

That makes sense:

test("foo").config(pending = true) { 
 //
}

And this is inverted - if it passes it fails and vice versa.