Faster test runs by suppressing output.

[ioquatix]

One of the slowest parts of running tests is collecting output.

If a test is successful, the output would never even be looked at.

I believe we can improve performance significantly by doing the following:

• Running all tests with null output.
• Collect failed tests.
• Re-run them with verbose logging and output buffering.
• Use that to log failures.

The question is whether we can make running the test suite with null output significantly faster.

We should also have hooks for verbose logging, e.g. enabling Console logger to be verbose. We might need to use a standard hook, e.g. $VERBOSE and/or $DEBUG should be set.