[Fix rubocop#7733] Fix rubocop-junit-formatter imcompatibility XML

## Summary

Fixes rubocop#7733.

This PR fixes rubocop-junit-formatter imcompatibility XML for JUnit formatter

The original rubocop-junit-formatter displayed all cops with or without offenses.
https://github.com/mikian/rubocop-junit-formatter/blob/v0.1.4/lib/rubocop/formatter/junit_formatter.rb#L9

It then displays all cops in XML elements, like the original rubocop-junit-formatter.

## Other Information

In the future, it would be preferable to display only enabled cops.
https://github.com/mikian/rubocop-junit-formatter/blob/v0.1.4/lib/rubocop/formatter/junit_formatter.rb#L7-L8

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 * [#7654](https://github.com/rubocop-hq/rubocop/issues/7654): Support `with_fixed_indentation` option for `Layout/ArrayAlignment` cop. ([@nikitasakov][])
 
+### Bug fixes
+
+* [#7733](https://github.com/rubocop-hq/rubocop/issues/7733): Fix rubocop-junit-formatter imcompatibility XML for JUnit formatter. ([@koic][])
+
 ## 0.80.1 (2020-02-29)
 
 ### Bug fixes

lib/rubocop/formatter/junit_formatter.rb

@@ -29,18 +29,29 @@ def initialize(output, options = {})
       end
 
       def file_finished(file, offenses)
-        offenses.group_by(&:cop_name).each do |cop_name, grouped_offenses|
+        # TODO: Returns all cops with the same behavior as
+        # the original rubocop-junit-formatter.
+        # https://github.com/mikian/rubocop-junit-formatter/blob/v0.1.4/lib/rubocop/formatter/junit_formatter.rb#L9
+        #
+        # In the future, it would be preferable to return only enabled cops.
+        Cop::Cop.all.each do |cop|
           REXML::Element.new('testcase', @testsuite).tap do |testcase|
-            testcase.attributes['classname'] = file.gsub(
-              /\.rb\Z/, ''
-            ).gsub("#{Dir.pwd}/", '').tr('/', '.')
-            testcase.attributes['name'] = cop_name
+            testcase.attributes['classname'] = classname_attribute_value(file)
+            testcase.attributes['name'] = cop.cop_name
 
-            add_failure_to(testcase, grouped_offenses, cop_name)
+            target_offenses = offenses.select do |offense|
+              offense.cop_name == cop.cop_name
+            end
+
+            add_failure_to(testcase, target_offenses, cop.cop_name)
           end
         end
       end
 
+      def classname_attribute_value(file)
+        file.gsub(/\.rb\Z/, '').gsub("#{Dir.pwd}/", '').tr('/', '.')
+      end
+
       def finished(_inspected_files)
         @document.write(output, 2)
       end

spec/rubocop/formatter/junit_formatter_spec.rb

@@ -6,8 +6,8 @@
   let(:output) { StringIO.new }
 
   describe '#file_finished' do
-    it 'displays parsable text' do
-      cop = RuboCop::Cop::Cop.new
+    before do
+      cop = RuboCop::Cop::Layout::SpaceInsideBlockBraces.new
       source_buffer = Parser::Source::Buffer.new('test', 1)
       source_buffer.source = %w[foo bar baz].join("\n")
 
@@ -26,30 +26,53 @@
       formatter.file_finished('test_2', cop.offenses)
 
       formatter.finished(nil)
+    end
 
-      expect(output.string).to eq(<<~XML.chop)
+    it 'displays start of parsable text' do
+      expect(output.string).to start_with(<<~XML)
         <?xml version='1.0'?>
         <testsuites>
           <testsuite name='rubocop'>
-            <testcase classname='test_1' name='Cop/Cop'>
-              <failure type='Cop/Cop' message='message 1'>
-                test:1:1
-              </failure>
-              <failure type='Cop/Cop' message='message 2'>
-                test:3:2
-              </failure>
-            </testcase>
-            <testcase classname='test_2' name='Cop/Cop'>
-              <failure type='Cop/Cop' message='message 1'>
-                test:1:1
-              </failure>
-              <failure type='Cop/Cop' message='message 2'>
-                test:3:2
-              </failure>
-            </testcase>
+      XML
+    end
+
+    it 'displays end of parsable text' do
+      expect(output.string).to end_with(<<~XML.chop)
           </testsuite>
         </testsuites>
       XML
     end
+
+    it "displays an offfense for `classname='test_1` in parsable text" do
+      expect(output.string).to include(<<-XML)
+    <testcase classname='test_1' name='Layout/SpaceInsideBlockBraces'>
+      <failure type='Layout/SpaceInsideBlockBraces' message='message 1'>
+        test:1:1
+      </failure>
+      <failure type='Layout/SpaceInsideBlockBraces' message='message 2'>
+        test:3:2
+      </failure>
+    </testcase>
+      XML
+    end
+
+    it "displays an offfense for `classname='test_2` in parsable text" do
+      expect(output.string).to include(<<-XML)
+    <testcase classname='test_2' name='Layout/SpaceInsideBlockBraces'>
+      <failure type='Layout/SpaceInsideBlockBraces' message='message 1'>
+        test:1:1
+      </failure>
+      <failure type='Layout/SpaceInsideBlockBraces' message='message 2'>
+        test:3:2
+      </failure>
+    </testcase>
+      XML
+    end
+
+    it 'displays a non-offfense element in parsable text' do
+      expect(output.string).to include(<<~XML)
+        <testcase classname='test_1' name='Style/Alias'/>
+      XML
+    end
   end
 end