The reason a test failed.
The reason a test run was invalid.
Test runners should report these to the user in whatever format is appropriate.
DEPRECATED. In the future, test runners should implement versions of this that make sense for their own environments.
Format test run failures in a reasonable way.
The reason a test failed.
Test runners can use this to provide nice output, e.g. by doing diffs on the two parts of an
Expect.equalfailure.