1 files changed, 111 insertions, 0 deletions
diff --git a/spec/lib/gitlab/database/migrations/instrumentation_spec.rb b/spec/lib/gitlab/database/migrations/instrumentation_spec.rb
new file mode 100644
index 00000000000..3804dc52a77
--- /dev/null
+++ b/spec/lib/gitlab/database/migrations/instrumentation_spec.rb
@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+require 'spec_helper'
+
+RSpec.describe Gitlab::Database::Migrations::Instrumentation do
+  describe '#observe' do
+    subject { described_class.new }
+
+    let(:migration) { 1234 }
+
+    it 'executes the given block' do
+      expect { |b| subject.observe(migration, &b) }.to yield_control
+    end
+
+    context 'behavior with observers' do
+      subject { described_class.new(observers).observe(migration) {} }
+
+      let(:observers) { [observer] }
+      let(:observer) { instance_double('Gitlab::Database::Migrations::Observers::MigrationObserver', before: nil, after: nil, record: nil) }
+
+      it 'calls #before, #after, #record on given observers' do
+        expect(observer).to receive(:before).ordered
+        expect(observer).to receive(:after).ordered
+        expect(observer).to receive(:record).ordered do |observation|
+          expect(observation.migration).to eq(migration)
+        end
+
+        subject
+      end
+
+      it 'ignores errors coming from observers #before' do
+        expect(observer).to receive(:before).and_raise('some error')
+
+        subject
+      end
+
+      it 'ignores errors coming from observers #after' do
+        expect(observer).to receive(:after).and_raise('some error')
+
+        subject
+      end
+
+      it 'ignores errors coming from observers #record' do
+        expect(observer).to receive(:record).and_raise('some error')
+
+        subject
+      end
+    end
+
+    context 'on successful execution' do
+      subject { described_class.new.observe(migration) {} }
+
+      it 'records walltime' do
+        expect(subject.walltime).not_to be_nil
+      end
+
+      it 'records success' do
+        expect(subject.success).to be_truthy
+      end
+
+      it 'records the migration version' do
+        expect(subject.migration).to eq(migration)
+      end
+    end
+
+    context 'upon failure' do
+      subject { described_class.new.observe(migration) { raise 'something went wrong' } }
+
+      it 'raises the exception' do
+        expect { subject }.to raise_error(/something went wrong/)
+      end
+
+      context 'retrieving observations' do
+        subject { instance.observations.first }
+
+        before do
+          instance.observe(migration) { raise 'something went wrong' }
+        rescue
+          # ignore
+        end
+
+        let(:instance) { described_class.new }
+
+        it 'records walltime' do
+          expect(subject.walltime).not_to be_nil
+        end
+
+        it 'records failure' do
+          expect(subject.success).to be_falsey
+        end
+
+        it 'records the migration version' do
+          expect(subject.migration).to eq(migration)
+        end
+      end
+    end
+
+    context 'sequence of migrations with failures' do
+      subject { described_class.new }
+
+      let(:migration1) { double('migration1', call: nil) }
+      let(:migration2) { double('migration2', call: nil) }
+
+      it 'records observations for all migrations' do
+        subject.observe('migration1') {}
+        subject.observe('migration2') { raise 'something went wrong' } rescue nil
+
+        expect(subject.observations.size).to eq(2)
+      end
+    end
+  end
+end