FastFail option for DefaultReporter

[chiku]

See the failure messages immediately while still running test suite with red-green style (dotted) format.

This is inspired from rspec-instafail https://github.com/grosser/rspec-instafail

When fast-fail is enabled, full messages would be printed on a test failure or errors. These failure messages are similar to those produced by SpecReporter.

The failure messages that DefaultReporter displays at the end of a test run are suppressed, since it would be redundant information.

The option to generate a fast-fail run is

MiniTest::Reporters.use! MiniTest::Reporters::DefaultReporter.new(:fast_fail => true)

And the output looks like

# Running tests:


MiniTestReportersTest::BadTest
  test_b                                                          FAIL
        --- expected
        +++ actual
        @@ -1,2 +1,2 @@
         "ab
        -c"
        +d"
        /Users/chirantan/personal_projects/minitest-reporters/test/gallery/bad_test.rb:14:in `test_b'

MiniTestReportersTest::BadTest
  test_a                                                          FAIL
        Expected: 1
          Actual: 2
        /Users/chirantan/personal_projects/minitest-reporters/test/gallery/bad_test.rb:6:in `test_a'

MiniTestReportersTest::BadTest
  test_boom                                                      ERROR
        A random exception
        /Users/chirantan/personal_projects/minitest-reporters/test/gallery/bad_test.rb:18:in `test_boom'
S..

Finished tests in 0.023226s, 258.3312 tests/s, 215.2760 assertions/s.

6 tests, 5 assertions, 2 failures, 1 errors, 1 skips

[kern]

Perfect! Thanks for this. I'll eventually get around to refactoring the reporters. There's a ton of messy code that could be factored out of DefaultReporter in particular.

Pushed in 0.14.0.