Instrument filtering, test

Author: mtodd

lib/html/pipeline.rb

@@ -84,10 +84,23 @@ def call(html, context = {}, result = nil)
       context = @default_context.merge(context)
       context = context.freeze
       result ||= @result_class.new
-      result[:output] = @filters.inject(html) { |doc, filter| filter.call(doc, context, result) }
+      result[:output] =
+        @filters.inject(html) do |doc, filter|
+          instrument "call_filter.html_pipeline", :filter => filter.name do
+            filter.call(doc, context, result)
+          end
+        end
       result
     end
 
+    def instrument(event, payload = nil, &block)
+      return yield unless instrumentation_service
+      instrumentation_service.instrument event, payload do
+        yield
+      end
+    end
+    attr_accessor :instrumentation_service
+
     # Like call but guarantee the value returned is a DocumentFragment.
     # Pipelines may return a DocumentFragment or a String. Callers that need a
     # DocumentFragment should use this method.

test/helpers/mocked_instrumentation_service.rb

@@ -0,0 +1,11 @@
+class MockedInstrumentationService
+  attr_reader :events
+  def initialize(events = [])
+    @events = events
+  end
+  def instrument(event, payload = nil)
+    res = yield
+    events << [event, payload, res]
+    res
+  end
+end

test/html/pipeline_test.rb

@@ -0,0 +1,31 @@
+require "test_helper"
+require "helpers/mocked_instrumentation_service"
+
+class HTML::PipelineTest < Test::Unit::TestCase
+  Pipeline = HTML::Pipeline
+  class TestFilter
+    def self.call(input, context, result)
+      input
+    end
+  end
+
+  def setup
+    @context = {}
+    @result_class = Hash
+    @pipeline = Pipeline.new [TestFilter], @context, @result_class
+  end
+
+  def test_filter_instrumentation
+    service = MockedInstrumentationService.new
+    @pipeline.instrumentation_service = service
+    filter("hello")
+    event, payload, res = service.events.pop
+    assert event, "event expected"
+    assert_equal "call_filter.html_pipeline", event
+    assert_equal TestFilter.name, payload[:filter]
+  end
+
+  def filter(input)
+    @pipeline.call(input)
+  end
+end