Fix pipeline config source specs and test it explicitly

spec/models/ci/pipeline_spec.rb

@@ -868,21 +868,17 @@ describe Ci::Pipeline, :mailer do
   end
 
   describe '#set_config_source' do
-    context 'on object initialisation' do
     context 'when pipelines does not contain needed data' do
-        let(:pipeline) do
-          Ci::Pipeline.new
-        end
-
       it 'defines source to be unknown' do
+        pipeline.set_config_source
+
         expect(pipeline).to be_unknown_source
       end
     end
 
     context 'when pipeline contains all needed data' do
       let(:pipeline) do
-          Ci::Pipeline.new(
-            project: project,
+        create(:ci_pipeline, project: project,
                              sha: '1234',
                              ref: 'master',
                              source: :push)
@@ -895,6 +891,8 @@ describe Ci::Pipeline, :mailer do
         end
 
         it 'defines source to be from repository' do
+          pipeline.set_config_source
+
           expect(pipeline).to be_repository_source
         end
 
@@ -920,7 +918,7 @@ describe Ci::Pipeline, :mailer do
           end
 
           it 'defines source to be auto devops' do
-              subject
+            pipeline.set_config_source
 
             expect(pipeline).to be_auto_devops_source
           end
@@ -928,7 +926,6 @@ describe Ci::Pipeline, :mailer do
       end
     end
   end
-  end
 
   describe '#ci_yaml_file' do
     let(:implied_yml) { Gitlab::Template::GitlabCiYmlTemplate.find('Auto-DevOps').content }