These are similar to `expect` and `expectAsync` except that they throw
exceptions rather than recording matcher failures as spec/suite failures.
They're intended to support using Jasmine matchers in testing-library's
`waitFor`, and also provide a way to integration-test custom matchers.
These funtions are not equivalent to `expect` and `expectAsync` and should
not be used in situations where you want a matcher failure to reliably fail
the spec. Whether that happens depends on the structure of the surrounding
code. In general, you should only use `throwUnless` when you expect
something (which could be your own code or library code like `waitFor`) to
catch the resulting exception.
Fixes#2003.
Fixes#1980.
e56bd3918b