Add new helper functions for checking function call results.
Review Request #9414 — Created Dec. 2, 2017 and submitted
This introduces new methods to check the results of function calls. It
returned()(for checking return values),
checking raised exception types),
raised exception types and exception messages), and
It also brings all call checks (
SpyCall, giving callers a
way to more conveniently determine results from individual calls.
Unit tests pass.