Add pipeline validation failure description

app/presenters/ci/pipeline_presenter.rb

@@ -8,7 +8,9 @@ module Ci
     # We use a class method here instead of a constant, allowing EE to redefine
     # the returned `Hash` more easily.
     def self.failure_reasons
-      { config_error: 'CI/CD YAML configuration error!' }
+      { unknown_failure: 'Unknown pipeline failure!',
+        config_error: 'CI/CD YAML configuration error!',
+        external_validation_failure: 'External pipeline validation failed!' }
     end
 
     presents :pipeline

ee/app/presenters/ee/ci/pipeline_presenter.rb

@@ -12,7 +12,8 @@ module EE
         def failure_reasons
           super.merge(
             activity_limit_exceeded: 'Pipeline activity limit exceeded!',
-            size_limit_exceeded: 'Pipeline size limit exceeded!'
+            size_limit_exceeded: 'Pipeline size limit exceeded!',
+            job_activity_limit_exceeded: 'Pipeline job activity limit exceeded!'
           )
         end
       end

spec/presenters/ci/pipeline_presenter_spec.rb

@@ -62,13 +62,19 @@ describe Ci::PipelinePresenter do
     end
   end
 
-  context '#failure_reason' do
-    context 'when pipeline has failure reason' do
-      it 'represents a failure reason sentence' do
-        pipeline.failure_reason = :config_error
+  describe '#failure_reason' do
+    context 'when pipeline has a failure reason' do
+      ::Ci::PipelineEnums.failure_reasons.keys.each do |failure_reason|
+        context "when failure reason is #{failure_reason}" do
+          before do
+            pipeline.failure_reason = failure_reason
+          end
 
-        expect(presenter.failure_reason)
-          .to eq 'CI/CD YAML configuration error!'
+          it 'represents a failure reason sentence' do
+            expect(presenter.failure_reason).to be_an_instance_of(String)
+            expect(presenter.failure_reason).not_to eq(failure_reason.to_s)
+          end
+        end
       end
     end