For assertions that contain function calls, displaying just the
expression is not helpful. For e.g.
Assertion failed
String.upcase("foo") == "Foo"
The learner is given no extra information to help them learn. Sure they
might consult the documentation (and should!), but perhaps a better
experience would be for us to inform the learner about the values it
encountered.
Assertion failed
String.upcase("foo") == "Foo"
left: "FOO"
right: "Foo"
Learner: 💡 ah hah! it upcases the whole string! 💫
