1 files changed, 60 insertions, 0 deletions
diff --git a/activesupport/test/notifications/instrumenter_test.rb b/activesupport/test/notifications/instrumenter_test.rb
new file mode 100644
index 0000000000..d5c9e82e9f
--- /dev/null
+++ b/activesupport/test/notifications/instrumenter_test.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/notifications/instrumenter"
+
+module ActiveSupport
+  module Notifications
+    class InstrumenterTest < ActiveSupport::TestCase
+      class TestNotifier
+        attr_reader :starts, :finishes
+
+        def initialize
+          @starts   = []
+          @finishes = []
+        end
+
+        def start(*args);  @starts << args; end
+        def finish(*args); @finishes << args; end
+      end
+
+      attr_reader :instrumenter, :notifier, :payload
+
+      def setup
+        super
+        @notifier     = TestNotifier.new
+        @instrumenter = Instrumenter.new @notifier
+        @payload = { foo: Object.new }
+      end
+
+      def test_instrument
+        called = false
+        instrumenter.instrument("foo", payload) {
+          called = true
+        }
+
+        assert called
+      end
+
+      def test_instrument_yields_the_payload_for_further_modification
+        assert_equal 2, instrumenter.instrument("awesome") { |p| p[:result] = 1 + 1 }
+        assert_equal 1, notifier.finishes.size
+        name, _, payload = notifier.finishes.first
+        assert_equal "awesome", name
+        assert_equal Hash[result: 2], payload
+      end
+
+      def test_start
+        instrumenter.start("foo", payload)
+        assert_equal [["foo", instrumenter.id, payload]], notifier.starts
+        assert_empty notifier.finishes
+      end
+
+      def test_finish
+        instrumenter.finish("foo", payload)
+        assert_equal [["foo", instrumenter.id, payload]], notifier.finishes
+        assert_empty notifier.starts
+      end
+    end
+  end
+end