Add around_test hook so instrumentation can be scoped per test

lib/inferno/test_runner.rb

@@ -59,44 +59,56 @@ def existing_test_result(runnable)
     end
 
     def run_test(test, scratch)
-      inputs = load_inputs(test)
-      input_json_string = inputs_as_json(test, inputs)
-
-      test_instance =
-        test.new(
-          inputs:,
-          test_session_id: test_session.id,
-          scratch:,
-          suite_options: test_session.suite_options_hash
-        )
+      around_test(test) do
+        inputs = load_inputs(test)
+        input_json_string = inputs_as_json(test, inputs)
 
-      result = evaluate_runnable_result(test, test_instance, inputs)
+        test_instance =
+          test.new(
+            inputs:,
+            test_session_id: test_session.id,
+            scratch:,
+            suite_options: test_session.suite_options_hash
+          )
 
-      outputs = save_outputs(test_instance)
-      output_json_string = JSON.generate(outputs)
+        result = evaluate_runnable_result(test, test_instance, inputs)
 
-      if result == 'wait'
-        test_runs_repo.mark_as_waiting(test_run.id, test_instance.identifier, test_instance.wait_timeout)
-      end
+        outputs = save_outputs(test_instance)
+        output_json_string = JSON.generate(outputs)
 
-      test_result = persist_result(
-        {
-          messages: test_instance.messages,
-          requests: test_instance.requests,
-          result:,
-          result_message: test_instance.result_message,
-          input_json: input_json_string,
-          output_json: output_json_string
-        }.merge(test.reference_hash)
-      )
+        if result == 'wait'
+          test_runs_repo.mark_as_waiting(test_run.id, test_instance.identifier, test_instance.wait_timeout)
+        end
 
-      # If running a single test, update its parents' results. If running a
-      # group or suite, #run_group handles updating the parents.
-      return test_result if test_run.test_id.blank?
+        test_result = persist_result(
+          {
+            messages: test_instance.messages,
+            requests: test_instance.requests,
+            result:,
+            result_message: test_instance.result_message,
+            input_json: input_json_string,
+            output_json: output_json_string
+          }.merge(test.reference_hash)
+        )
 
-      update_parent_result(test.parent)
+        # If running a single test, update its parents' results. If running a
+        # group or suite, #run_group handles updating the parents.
+        update_parent_result(test.parent) if test_run.test_id.present?
 
-      test_result
+        test_result
+      end
+    end
+
+    # Wraps the execution of a single test. Override or prepend this method to run
+    # instrumentation around each test, for example to emit a distinct trace, span,
+    # or timing metric per test instead of one that spans the whole run. The default
+    # implementation just yields.
+    #
+    # @param test [Class] the test being run (an Inferno::Entities::Test subclass)
+    # @yield executes the test and returns its result
+    # @return the value returned by the block
+    def around_test(_test)
+      yield
     end
 
     def check_inputs(test, _test_instance, inputs)

spec/inferno/test_runner_spec.rb

@@ -93,6 +93,35 @@ def error_results_message(error_results)
         expect(output['type']).to be_present
       end
     end
+
+    it 'wraps each test with #around_test' do
+      wrapped = []
+      allow(runner).to receive(:around_test).and_wrap_original do |_original, test, &block|
+        wrapped << test
+        block.call
+      end
+
+      results = runner.start
+      test_results = results.select { |result| result.runnable < Inferno::Entities::Test }
+
+      expect(wrapped).to_not be_empty
+      expect(wrapped).to all(be < Inferno::Entities::Test)
+      expect(wrapped.length).to eq(test_results.length)
+    end
+  end
+
+  describe '#around_test' do
+    let(:test_run) do
+      repo_create(:test_run, runnable: { test_group_id: 'demo-simple_group' }, test_session_id: test_session.id)
+    end
+
+    it 'yields by default' do
+      expect { |block| runner.around_test(nil, &block) }.to yield_control
+    end
+
+    it 'returns the value of the block by default' do
+      expect(runner.around_test(nil) { :test_result }).to eq(:test_result)
+    end
   end
 
   describe 'when running wait group' do