Adds a `js-` class to allow for specs

Rspec was using a CSS class to check if the content
was being rendered. Since the CSS has changed, the specs failed
This commit replaces the CSS class with a `js-` prepended one
to guarantee changing CSS won't break a pipeline

app/assets/javascripts/vue_merge_request_widget/mr_widget_options.vue

@@ -270,6 +270,7 @@ export default {
     />
     <grouped-test-reports-app
       v-if="mr.testResultsPath"
+      class="js-reports-container"
       :endpoint="mr.testResultsPath"
     />
     <div class="mr-section-container">

spec/features/merge_request/user_sees_merge_widget_spec.rb

@@ -423,7 +423,7 @@ describe 'Merge request > User sees merge widget', :js do
         end
 
         it 'shows test reports summary which includes the new failure' do
-          within(".mr-section-container") do
+          within(".js-reports-container") do
             click_button 'Expand'
 
             expect(page).to have_content('Test summary contained 1 failed test result out of 2 total tests')
@@ -438,7 +438,7 @@ describe 'Merge request > User sees merge widget', :js do
 
         context 'when user clicks the new failure' do
           it 'shows the test report detail' do
-            within(".mr-section-container") do
+            within(".js-reports-container") do
               click_button 'Expand'
 
               within(".js-report-section-container") do
@@ -468,7 +468,7 @@ describe 'Merge request > User sees merge widget', :js do
         end
 
         it 'shows test reports summary which includes the existing failure' do
-          within(".mr-section-container") do
+          within(".js-reports-container") do
             click_button 'Expand'
 
             expect(page).to have_content('Test summary contained 1 failed test result out of 2 total tests')
@@ -483,7 +483,7 @@ describe 'Merge request > User sees merge widget', :js do
 
         context 'when user clicks the existing failure' do
           it 'shows test report detail of it' do
-            within(".mr-section-container") do
+            within(".js-reports-container") do
               click_button 'Expand'
 
               within(".js-report-section-container") do
@@ -519,7 +519,7 @@ describe 'Merge request > User sees merge widget', :js do
         end
 
         it 'shows test reports summary which includes the resolved failure' do
-          within(".mr-section-container") do
+          within(".js-reports-container") do
             click_button 'Expand'
 
             expect(page).to have_content('Test summary contained 1 fixed test result out of 2 total tests')
@@ -533,7 +533,7 @@ describe 'Merge request > User sees merge widget', :js do
 
         context 'when user clicks the resolved failure' do
           it 'shows test report detail of it' do
-            within(".mr-section-container") do
+            within(".js-reports-container") do
               click_button 'Expand'
 
               within(".js-report-section-container") do