Add tests for QA test selectors sanity scenario

2 files changed, 42 insertions, 2 deletions

diff --git a/qa/qa/scenario/test/sanity/selectors.rb b/qa/qa/scenario/test/sanity/selectors.rb
index 365eb3315f8..157336be66f 100644
--- a/qa/qa/scenario/test/sanity/selectors.rb
+++ b/qa/qa/scenario/test/sanity/selectors.rb
@@ -15,7 +15,7 @@ module QA
             validators.map(&:errors).flatten.tap do |errors|
               break if errors.none?
 
-              STDERR.puts <<~EOS
+              $stderr.puts <<~EOS
                 GitLab QA sanity selectors validation test detected problems
                 with your merge request!
 
@@ -40,7 +40,7 @@ module QA
 
               EOS
 
-              STDERR.puts errors
+              $stderr.puts errors
             end
 
             validators.each(&:validate!)
diff --git a/qa/spec/scenario/test/sanity/selectors_spec.rb b/qa/spec/scenario/test/sanity/selectors_spec.rb
new file mode 100644
index 00000000000..a64a60fa119
--- /dev/null
+++ b/qa/spec/scenario/test/sanity/selectors_spec.rb
@@ -0,0 +1,40 @@
+describe QA::Scenario::Test::Sanity::Selectors do
+  let(:validator) { spy('validator') }
+
+  before do
+    stub_const('QA::Page::Validator', validator)
+  end
+
+  context 'when there are errors detected' do
+    before do
+      allow(validator).to receive(:errors).and_return(['some error'])
+    end
+
+    it 'outputs information about errors' do
+      expect { described_class.perform }
+        .to output(/some error/).to_stderr
+
+      expect { described_class.perform }
+        .to output(/electors validation test detected problems/)
+        .to_stderr
+    end
+  end
+
+  context 'when there are no errors detected' do
+    before do
+      allow(validator).to receive(:errors).and_return([])
+    end
+
+    it 'processes pages module' do
+      described_class.perform
+
+      expect(validator).to have_received(:new).with(QA::Page)
+    end
+
+    it 'triggers validation' do
+      described_class.perform
+
+      expect(validator).to have_received(:validate!)
+    end
+  end
+end