abstract infix fun assertIt(assertionCreator: Assert<V>.() -> Unit): Assert<T>
Makes the assertion that the Assert.subject contains the previously specified key and that the corresponding value holds all assertions the given assertionCreator might create for it.
AssertionError - Might throw an AssertionError if a created Assertions (by calling assertionCreator)
does not hold.
IllegalArgumentException - in case the given assertionCreator did not create a single assertion.
Return
This plant to support a fluent API.