Move Project#latest_successful_builds_for to project_spec.rb

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13173313

spec/models/build_spec.rb

@@ -674,40 +674,6 @@ describe Ci::Build, models: true do
     end
   end
 
-  describe 'Project#latest_successful_builds_for' do
-    let!(:build) do
-      create(:ci_build, :artifacts, :success, pipeline: pipeline)
-    end
-
-    context 'with succeed pipeline' do
-      it 'returns builds for ref for default_branch' do
-        builds = project.latest_successful_builds_for
-
-        expect(builds).to contain_exactly(build)
-      end
-
-      it 'returns empty relation if the build cannot be found' do
-        builds = project.latest_successful_builds_for('TAIL')
-
-        expect(builds).to be_kind_of(ActiveRecord::Relation)
-        expect(builds).to be_empty
-      end
-    end
-
-    context 'with pending pipeline' do
-      before do
-        pipeline.update(status: 'pending')
-      end
-
-      it 'returns empty relation' do
-        builds = project.latest_successful_builds_for
-
-        expect(builds).to be_kind_of(ActiveRecord::Relation)
-        expect(builds).to be_empty
-      end
-    end
-  end
-
   describe '#manual?' do
     before do
       build.update(when: value)

spec/models/project_spec.rb

@@ -1114,6 +1114,49 @@ describe Project, models: true do
     end
   end
 
+  describe '#latest_successful_builds_for' do
+    let(:project) { create(:project) }
+
+    let(:pipeline) do
+      create(:ci_pipeline, project: project,
+                           sha: project.commit.id,
+                           ref: project.default_branch,
+                           status: 'success')
+    end
+
+    let!(:build) do
+      create(:ci_build, :artifacts, :success, pipeline: pipeline)
+    end
+
+    context 'with succeed pipeline' do
+      it 'returns builds for ref for default_branch' do
+        builds = project.latest_successful_builds_for
+
+        expect(builds).to contain_exactly(build)
+      end
+
+      it 'returns empty relation if the build cannot be found' do
+        builds = project.latest_successful_builds_for('TAIL')
+
+        expect(builds).to be_kind_of(ActiveRecord::Relation)
+        expect(builds).to be_empty
+      end
+    end
+
+    context 'with pending pipeline' do
+      before do
+        pipeline.update(status: 'pending')
+      end
+
+      it 'returns empty relation' do
+        builds = project.latest_successful_builds_for
+
+        expect(builds).to be_kind_of(ActiveRecord::Relation)
+        expect(builds).to be_empty
+      end
+    end
+  end
+
   describe '.where_paths_in' do
     context 'without any paths' do
       it 'returns an empty relation' do