Test readability and error reporting

[bettio]

A number of tests rely on a number of old tricks to inform about what failed, since quite some time, when failing pattern matching line number is reported.
Tests should make more use of pattern matching so we can get line number information.

Caveats:

• line numbers are reported only for BEAM files generated with some specific OTP versions
• in case of corruption the expected value might "leak" leading to a false negatives, so tests focused on VM features should avoid direct reference to expected values