1 files changed, 99 insertions, 0 deletions
diff --git a/spec/lib/gitlab/metrics/sli_spec.rb b/spec/lib/gitlab/metrics/sli_spec.rb
new file mode 100644
index 00000000000..8ba4bf29568
--- /dev/null
+++ b/spec/lib/gitlab/metrics/sli_spec.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+RSpec.describe Gitlab::Metrics::Sli do
+  let(:prometheus) { double("prometheus") }
+
+  before do
+    stub_const("Gitlab::Metrics", prometheus)
+  end
+
+  describe 'Class methods' do
+    before do
+      described_class.instance_variable_set(:@known_slis, nil)
+    end
+
+    describe '.[]' do
+      it 'warns about an uninitialized SLI but returns and stores a new one' do
+        sli = described_class[:bar]
+
+        expect(described_class[:bar]).to be(sli)
+      end
+
+      it 'returns the same object for multiple accesses' do
+        sli = described_class.initialize_sli(:huzzah, [])
+
+        2.times do
+          expect(described_class[:huzzah]).to be(sli)
+        end
+      end
+    end
+
+    describe '.initialized?' do
+      before do
+        fake_total_counter(:boom)
+        fake_success_counter(:boom)
+      end
+
+      it 'is true when an SLI was initialized with labels' do
+        expect { described_class.initialize_sli(:boom, [{ hello: :world }]) }
+          .to change { described_class.initialized?(:boom) }.from(false).to(true)
+      end
+
+      it 'is false when an SLI was not initialized with labels' do
+        expect { described_class.initialize_sli(:boom, []) }
+          .not_to change { described_class.initialized?(:boom) }.from(false)
+      end
+    end
+  end
+
+  describe '#initialize_counters' do
+    it 'initializes counters for the passed label combinations' do
+      counters = [fake_total_counter(:hey), fake_success_counter(:hey)]
+
+      described_class.new(:hey).initialize_counters([{ foo: 'bar' }, { foo: 'baz' }])
+
+      expect(counters).to all(have_received(:get).with({ foo: 'bar' }))
+      expect(counters).to all(have_received(:get).with({ foo: 'baz' }))
+    end
+  end
+
+  describe "#increment" do
+    let!(:sli) { described_class.new(:heyo) }
+    let!(:total_counter) { fake_total_counter(:heyo) }
+    let!(:success_counter) { fake_success_counter(:heyo) }
+
+    it 'increments both counters for labels successes' do
+      sli.increment(labels: { hello: "world" }, success: true)
+
+      expect(total_counter).to have_received(:increment).with({ hello: 'world' })
+      expect(success_counter).to have_received(:increment).with({ hello: 'world' })
+    end
+
+    it 'only increments the total counters for labels when not successful' do
+      sli.increment(labels: { hello: "world" }, success: false)
+
+      expect(total_counter).to have_received(:increment).with({ hello: 'world' })
+      expect(success_counter).not_to have_received(:increment).with({ hello: 'world' })
+    end
+  end
+
+  def fake_prometheus_counter(name)
+    fake_counter = double("prometheus counter: #{name}")
+
+    allow(fake_counter).to receive(:get)
+    allow(fake_counter).to receive(:increment)
+    allow(prometheus).to receive(:counter).with(name.to_sym, anything).and_return(fake_counter)
+
+    fake_counter
+  end
+
+  def fake_total_counter(name)
+    fake_prometheus_counter("gitlab_sli:#{name}:total")
+  end
+
+  def fake_success_counter(name)
+    fake_prometheus_counter("gitlab_sli:#{name}:success_total")
+  end
+end