added testcases for uninstrumentation for starlette with metrics

Author: rahulmukherjee68

Diff for: instrumentation/opentelemetry-instrumentation-starlette/tests/test_starlette_instrumentation.py

@@ -145,6 +145,43 @@ def test_starlette_metrics(self):
                                 attr, _recommended_attrs[metric.name]
                             )
         self.assertTrue(number_data_point_seen and histogram_data_point_seen)
+    
+    def test_basic_post_request_metric_success(self):
+        start = default_timer()
+        self._client.post("/foobar")
+        duration = max(round((default_timer() - start) * 1000), 0)
+        metrics_list = self.memory_metrics_reader.get_metrics_data()
+        for metric in (
+            metrics_list.resource_metrics[0].scope_metrics[0].metrics
+        ):
+            for point in list(metric.data.data_points):
+                if isinstance(point, HistogramDataPoint):
+                    self.assertEqual(point.count, 1)
+                    self.assertAlmostEqual(duration, point.sum, delta=30)
+                if isinstance(point, NumberDataPoint):
+                    self.assertEqual(point.value, 0)
+
+    def test_metric_uninstrument(self):
+        # instrumenting class and creating app to send request
+        self._instrumentor.instrument()
+        app = self._create_starlette_app()
+        client = TestClient(app)
+        client.get("/foobar")
+        # uninstrumenting class and creating the app again
+        self._instrumentor.uninstrument()
+        app = self._create_starlette_app()
+        client = TestClient(app)
+        client.get("/foobar")
+
+        metrics_list = self.memory_metrics_reader.get_metrics_data()
+        for metric in (
+            metrics_list.resource_metrics[0].scope_metrics[0].metrics
+        ):
+            for point in list(metric.data.data_points):
+                if isinstance(point, HistogramDataPoint):
+                    self.assertEqual(point.count, 1)
+                if isinstance(point, NumberDataPoint):
+                    self.assertEqual(point.value, 0)
 
     @staticmethod
     def _create_starlette_app():