Add Tests for Metrics::Concern

lib/gitlab/metrics/concern.rb

@@ -12,7 +12,7 @@ module Gitlab
         private
 
         def define_metric(type, name, opts = {}, &block)
-          if instance_methods(false).include?(name)
+          if respond_to?(name)
             raise ArgumentError, "metrics method #{name} already exists"
           end
 
@@ -71,7 +71,7 @@ module Gitlab
         # @param [Symbol] name
         # @param [Hash] opts
         def fetch_gauge(name, opts = {}, &block)
-          fetch_metric(:counter, name, opts, &block)
+          fetch_metric(:gauge, name, opts, &block)
         end
 
         # Fetch and/or initialize histogram metric
@@ -99,7 +99,7 @@ module Gitlab
         # @param [Symbol] name
         # @param [Hash] opts
         def define_gauge(name, opts = {}, &block)
-          define_metric(:counter, name, opts, &block)
+          define_metric(:gauge, name, opts, &block)
         end
 
         # Define metric accessor method for a Histogram

spec/lib/gitlab/metrics/concern_spec.rb

@@ -0,0 +1,101 @@
+require 'spec_helper'
+
+describe Gitlab::Metrics::Concern do
+  subject { Class.new { include Gitlab::Metrics::Concern } }
+
+  let(:null_metric) { Gitlab::Metrics::NullMetric.new }
+
+  shared_context 'metric' do |metric_type, *args|
+    let(:docstring) { 'description' }
+    let(:metric) { :sample_metric }
+
+    describe "#define_#{metric_type}" do
+      let(:define_method) { "define_#{metric_type}".to_sym }
+
+      context 'metrics access method not defined' do
+        it "defines metrics accessing method" do
+          expect(subject).not_to respond_to(metric)
+
+          subject.send(define_method, metric, docstring: docstring)
+
+          expect(subject).to respond_to(metric)
+        end
+      end
+
+      context 'metrics access method defined' do
+        before do
+          subject.send(define_method, metric, docstring: docstring)
+        end
+
+        it 'raises error when trying to redefine method' do
+          expect { subject.send(define_method, metric, docstring: docstring) }.to raise_error(ArgumentError)
+        end
+
+        context 'metric is not cached' do
+          it 'calls fetch_metric' do
+            expect(subject).to receive(:fetch_metric).with(metric_type, metric, docstring: docstring)
+
+            subject.send(metric)
+          end
+        end
+
+        context 'metric is cached' do
+          before do
+            subject.send(metric)
+          end
+
+          it 'returns cached metric' do
+            expect(subject).not_to receive(:fetch_metric)
+
+            subject.send(metric)
+          end
+        end
+      end
+    end
+
+    describe "#fetch_#{metric_type}" do
+      let(:fetch_method) { "fetch_#{metric_type}".to_sym }
+
+      context "when #{metric_type} fetched first time" do
+        it 'initializes counter metric' do
+          allow(Gitlab::Metrics).to receive(metric_type).and_return(null_metric)
+
+          subject.send(fetch_method, metric, docstring: docstring)
+
+          expect(Gitlab::Metrics).to have_received(metric_type).with(metric, docstring, *args)
+        end
+      end
+
+      context "when #{metric_type} is fetched second time" do
+        before do
+          subject.send(fetch_method, metric, docstring: docstring)
+        end
+
+        it 'uses class metric cache' do
+          expect(Gitlab::Metrics).not_to receive(metric_type)
+
+          subject.send(fetch_method, metric, docstring: docstring)
+        end
+
+        context 'when metric is reloaded' do
+          before do
+            subject.reload_metric!(metric)
+          end
+
+          it "initializes #{metric_type} metric" do
+            allow(Gitlab::Metrics).to receive(metric_type).and_return(null_metric)
+
+            subject.send(fetch_method, metric, docstring: docstring)
+
+            expect(Gitlab::Metrics).to have_received(metric_type).with(metric, docstring, *args)
+          end
+        end
+      end
+    end
+
+  end
+
+  include_examples 'metric', :counter, {}
+  include_examples 'metric', :gauge, {}, :all
+  include_examples 'metric', :histogram, {}, [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10]
+end