test refactoring to deal with time flakiness

Author: sbfaulkner

test/limiter/mixin_test.rb

@@ -4,6 +4,9 @@
 
 module Limiter
   class MixinTest < Minitest::Test
+    include FakeSleep
+    include AssertElapsed
+
     COUNT = 50
     RATE = 1
     INTERVAL = 1
@@ -26,34 +29,23 @@ def tick
 
     def setup
       super
-      RateQueue.send(:define_method, :sleep) { |i| Timecop.travel(Time.now + i) }
-    end
-
-    def teardown
-      RateQueue.send(:remove_method, :sleep)
-      super
+      @object = MixinTestClass.new
     end
 
     def test_method_is_rate_limited
-      object = MixinTestClass.new
-
-      start = Time.now
-
-      COUNT.times do
-        object.tick
+      assert_elapsed(COUNT.to_f / RATE - 1) do
+        COUNT.times do
+          @object.tick
+        end
       end
-
-      assert_equal (start.to_i + (COUNT / RATE) - 1).to_i, Time.now.to_i
     end
 
     def test_original_method_is_called
-      object = MixinTestClass.new
-
       COUNT.times do
-        object.tick
+        @object.tick
       end
 
-      assert_equal COUNT, object.ticks
+      assert_equal COUNT, @object.ticks
     end
   end
 end

test/limiter/rate_queue_test.rb

@@ -4,42 +4,36 @@
 
 module Limiter
   class RateQueueTest < Minitest::Test
+    include FakeSleep
+    include AssertElapsed
+
     COUNT = 50
     RATE = 1
     INTERVAL = 1
 
     def setup
       super
       @queue = RateQueue.new(RATE, interval: INTERVAL)
-      RateQueue.send(:define_method, :sleep) { |i| Timecop.travel(Time.now + i) }
-    end
-
-    def teardown
-      RateQueue.send(:remove_method, :sleep)
-      super
     end
 
     def test_shift_is_rate_limited
-      start = Time.now
-
-      COUNT.times do
-        @queue.shift
+      assert_elapsed(COUNT.to_f / RATE - 1) do
+        COUNT.times do
+          @queue.shift
+        end
       end
-
-      assert_equal (start.to_i + (COUNT / RATE) - 1).to_i, Time.now.to_i
     end
 
     def test_shift_is_rate_limited_across_multiple_threads
-      threads = Array.new(COUNT) do
-        Thread.new do
-          @queue.shift
-          Time.now
+      assert_elapsed(COUNT.to_f / RATE - 1) do
+        threads = Array.new(COUNT) do
+          Thread.new do
+            @queue.shift
+          end
         end
-      end
-
-      times = threads.map(&:value)
 
-      assert_equal (times.min + (COUNT / RATE) - 1).to_i, times.max.to_i
+        threads.each(&:join)
+      end
     end
   end
 end

test/test_helper.rb

@@ -5,3 +5,29 @@
 
 require 'minitest/autorun'
 require 'timecop'
+
+module Limiter
+  module FakeSleep
+    def setup
+      super
+      RateQueue.send(:define_method, :sleep) { |i| Timecop.travel(Time.now + i) }
+    end
+
+    def teardown
+      RateQueue.send(:remove_method, :sleep)
+      super
+    end
+  end
+
+  module AssertElapsed
+    def assert_elapsed(interval)
+      started_at = Time.now.to_f
+
+      yield
+
+      completed_at = Time.now.to_f
+
+      assert_in_delta started_at + interval, completed_at, 1.1
+    end
+  end
+end