isInstanceOf() should issue a better failure message when the tested object is null

[doublep]

Background: I often use assertThat (catchException (...)).isInstanceOf (...) instead of assertThatThrowBy ... or something similar. I guess it's a matter of taste what to prefer. I have noticed that isInstanceOf() issues a pretty confusing failure message when nothing is actually thrown, i.e. when catchException() returns null.

To illustrate, when I run this code:

assertThat (catchException (() -> { })).isInstanceOf (RuntimeException.class);

I get this failure message:

Expecting actual not to be null

In comparison, when the tested object is not null, but of a wrong class, failure message is much more clear. For example:

assertThat (catchException (() -> { throw new Exception (); })).isInstanceOf (RuntimeException.class);

gives me this:

Expecting actual throwable to be an instance of:
  java.lang.RuntimeException
but was:
  java.lang.Exception

Suggestion

Rephrase the null-case message somewhat like this:

Expecting actual throwable to be an instance of:
  java.lang.RuntimeException
but was:
  null (no throwable)