Improce specs of authentication activity class methods

spec/lib/gitlab/auth/activity_spec.rb

@@ -1,14 +1,30 @@
-require 'spec_helper'
+require 'fast_spec_helper'
 
 describe Gitlab::Auth::Activity do
-  describe '#each_counter' do
+  describe '.each_counter' do
     it 'has all static counters defined' do
       described_class.each_counter do |counter|
         expect(described_class).to respond_to(counter)
       end
     end
 
-    # todo incrementer pairs
-    # todo all metrics starting with `user`_
+    it 'has all static incrementers defined' do
+      described_class.each_counter do |counter|
+        expect(described_class).to respond_to("#{counter}_increment!")
+      end
+    end
+
+    it 'has all counters starting with `user_`' do
+      described_class.each_counter do |counter|
+        expect(counter).to start_with('user_')
+      end
+    end
+
+    it 'yields counter method, name and description' do
+      described_class.each_counter do |method, name, description|
+        expect(method).to eq "#{name}_counter"
+        expect(description).to start_with('Counter of')
+      end
+    end
   end
 end