Add fail fast to test runner.

Passing `--fail-fast` to the test runner will now abort the test run
on the first failure. The run continues on any unexpected errors.

railties/CHANGELOG.md

@@ -1,3 +1,35 @@
+*   Add fail fast to `bin/rails test`
+
+    Adding `--fail-fast` or `-f` when running tests will interrupt the run on
+    the first failure:
+
+    ```
+    # Running:
+
+    ................................................S......E
+
+    ArgumentError: Wups! Bet you didn't expect this!
+        test/models/bunny_test.rb:19:in `block in <class:BunnyTest>'
+
+    bin/rails test test/models/bunny_test.rb:18
+
+    ....................................F
+
+    This failed
+
+    bin/rails test test/models/bunny_test.rb:14
+
+    Interrupted. Exiting...
+
+
+    Finished in 0.051427s, 1808.3872 runs/s, 1769.4972 assertions/s.
+
+    ```
+
+    Note that any unexpected errors don't abort the run.
+
+    *Kasper Timm Hansen*
+
 *   Add inline output to `bin/rails test`
 
     Any failures or errors (and skips if running in verbose mode) are output

railties/lib/rails/test_unit/minitest_plugin.rb

@@ -33,6 +33,11 @@ module Minitest
       options[:output_inline] = false
     end
 
+    opts.on("-f", "--fail-fast",
+            "Abort test run on first failure") do
+      options[:fail_fast] = true
+    end
+
     options[:patterns] = opts.order!
   end
 

railties/lib/rails/test_unit/reporter.rb

@@ -17,6 +17,10 @@ module Rails
         io.puts format_rerun_snippet(result)
         io.puts
       end
+
+      if fail_fast? && result.failure && !result.error? && !result.skipped?
+        raise Interrupt
+      end
     end
 
     def report
@@ -48,6 +52,10 @@ module Rails
         options.fetch(:output_inline, true)
       end
 
+      def fail_fast?
+        options[:fail_fast]
+      end
+
       def format_rerun_snippet(result)
         location, line = result.method(result.name).source_location
         "#{self.executable} #{relative_path_for(location)}:#{line}"

railties/test/application/test_runner_test.rb

@@ -355,6 +355,21 @@ module ApplicationTests
       assert_match %r{Running:\n\nF\n\nwups!\n\nbin/rails test test/models/post_test.rb:4}, output
     end
 
+    def test_fail_fast
+      app_file 'test/models/post_test.rb', <<-RUBY
+        require 'test_helper'
+
+        class PostTest < ActiveSupport::TestCase
+          def test_post
+            assert false, 'wups!'
+          end
+        end
+      RUBY
+
+      assert_match(/Interrupt/,
+        capture(:stderr) { run_test_command('test/models/post_test.rb --fail-fast') })
+    end
+
     def test_raise_error_when_specified_file_does_not_exist
       error = capture(:stderr) { run_test_command('test/not_exists.rb') }
       assert_match(%r{cannot load such file.+test/not_exists\.rb}, error)

railties/test/test_unit/reporter_test.rb

@@ -86,6 +86,30 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     assert_no_match 'Failed tests:', @output.string
   end
 
+  test "fail fast interrupts run on failure" do
+    fail_fast = Rails::TestUnitReporter.new @output, fail_fast: true
+    interrupt_raised = false
+
+    # Minitest passes through Interrupt, catch it manually.
+    begin
+      fail_fast.record(failed_test)
+    rescue Interrupt
+      interrupt_raised = true
+    ensure
+      assert interrupt_raised, 'Expected Interrupt to be raised.'
+    end
+  end
+
+  test "fail fast does not interrupt run errors or skips" do
+    fail_fast = Rails::TestUnitReporter.new @output, fail_fast: true
+
+    fail_fast.record(errored_test)
+    assert_no_match 'Failed tests:', @output.string
+
+    fail_fast.record(skipped_test)
+    assert_no_match 'Failed tests:', @output.string
+  end
+
   private
   def assert_rerun_snippet_count(snippet_count)
     assert_equal snippet_count, @output.string.scan(%r{^bin/rails test }).size