make it possible to customize the executable inside rereun snippets.

In the Rails repository we use a `bin/test` executable to run our tests.
However the rerun snippets still included `bin/rails test`:

BEFORE:
```
Failed tests:

bin/rails test test/cases/adapters/postgresql/schema_test.rb:91
```

AFTER:
```
Failed tests:

bin/test test/cases/adapters/postgresql/schema_test.rb:91
```

3 files changed, 23 insertions, 1 deletions

diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 3536929d00..ca07ff349c 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Make it possible to customize the executable inside rerun snippets.
+
+    *Yves Senn*
+
 *   Add support for API only apps.
     Middleware stack was slimmed down and it has only the needed
     middleware for API apps & generators generates the right files,
diff --git a/railties/lib/rails/test_unit/reporter.rb b/railties/lib/rails/test_unit/reporter.rb
index bfdc9754d4..faf551f381 100644
--- a/railties/lib/rails/test_unit/reporter.rb
+++ b/railties/lib/rails/test_unit/reporter.rb
@@ -1,7 +1,11 @@
+require "active_support/core_ext/class/attribute"
 require "minitest"
 
 module Rails
   class TestUnitReporter < Minitest::StatisticsReporter
+    class_attribute :executable
+    self.executable = "bin/rails test"
+
     def report
       return if results.empty?
       io.puts
@@ -15,7 +19,7 @@ module Rails
       filtered_results.reject!(&:skipped?) unless options[:verbose]
       filtered_results.map do |result|
         location, line = result.method(result.name).source_location
-        "bin/rails test #{relative_path_for(location)}:#{line}"
+        "#{self.executable} #{relative_path_for(location)}:#{line}"
       end.join "\n"
     end
 
diff --git a/railties/test/test_unit/reporter_test.rb b/railties/test/test_unit/reporter_test.rb
index 77883612f5..d619a3e515 100644
--- a/railties/test/test_unit/reporter_test.rb
+++ b/railties/test/test_unit/reporter_test.rb
@@ -43,6 +43,20 @@ class TestUnitReporterTest < ActiveSupport::TestCase
     assert_rerun_snippet_count 1
   end
 
+  test "allows to customize the executable in the rerun snippet" do
+    original_executable = Rails::TestUnitReporter.executable
+    begin
+      Rails::TestUnitReporter.executable = "bin/test"
+      verbose = Rails::TestUnitReporter.new @output, verbose: true
+      @reporter.record(failed_test)
+      @reporter.report
+
+      assert_match %r{^bin/test .*test/test_unit/reporter_test.rb:6$}, @output.string
+    ensure
+      Rails::TestUnitReporter.executable = original_executable
+    end
+  end
+
   private
   def assert_rerun_snippet_count(snippet_count)
     assert_equal snippet_count, @output.string.scan(%r{^bin/rails test }).size