Add basic test of ASP.NET Core request metric (#2186)

* Add basic test of ASP.NET Core request metric

* Remove netcoreapp2.1

* Clarify comments

Co-authored-by: Cijo Thomas <cithomas@microsoft.com>

test/OpenTelemetry.Instrumentation.AspNetCore.Tests/MetricTests.cs

@@ -0,0 +1,129 @@
+// <copyright file="MetricTests.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.Testing;
+using OpenTelemetry.Metrics;
+using OpenTelemetry.Tests;
+using OpenTelemetry.Trace;
+#if NETCOREAPP3_1
+using TestApp.AspNetCore._3._1;
+#else
+using TestApp.AspNetCore._5._0;
+#endif
+using Xunit;
+
+namespace OpenTelemetry.Instrumentation.AspNetCore.Tests
+{
+    public class MetricTests
+        : IClassFixture<WebApplicationFactory<Startup>>, IDisposable
+    {
+        private readonly WebApplicationFactory<Startup> factory;
+        private MeterProvider meterProvider = null;
+
+        public MetricTests(WebApplicationFactory<Startup> factory)
+        {
+            this.factory = factory;
+        }
+
+        [Fact]
+        public void AddAspNetCoreInstrumentation_BadArgs()
+        {
+            MeterProviderBuilder builder = null;
+            Assert.Throws<ArgumentNullException>(() => builder.AddAspNetCoreInstrumentation());
+        }
+
+        [Fact]
+        public async Task RequestMetricIsCaptured()
+        {
+            var metricItems = new List<MetricItem>();
+            var metricExporter = new TestExporter<MetricItem>(ProcessExport);
+
+            void ProcessExport(Batch<MetricItem> batch)
+            {
+                foreach (var metricItem in batch)
+                {
+                    metricItems.Add(metricItem);
+                }
+            }
+
+            this.meterProvider = Sdk.CreateMeterProviderBuilder()
+                .AddAspNetCoreInstrumentation()
+                .AddMetricProcessor(new PushMetricProcessor(exporter: metricExporter, exportIntervalMs: 10, isDelta: true))
+                .Build();
+
+            using (var client = this.factory.CreateClient())
+            {
+                var response = await client.GetAsync("/api/values");
+                response.EnsureSuccessStatusCode();
+            }
+
+            // Wait for at least two exporter invocations
+            WaitForMetricItems(metricItems, 2);
+
+            this.meterProvider.Dispose();
+
+            // There should be more than one result here since we waited for at least two exporter invocations.
+            // The exporter continues to receive a metric even if it has not changed since the last export.
+            var requestMetrics = metricItems
+                .SelectMany(item => item.Metrics.Where(metric => metric.Name == "http.server.request_count"))
+                .ToArray();
+
+            Assert.True(requestMetrics.Length > 1);
+
+            var metric = requestMetrics[0] as ISumMetric;
+            Assert.NotNull(metric);
+            Assert.Equal(1L, metric.Sum.Value);
+
+            var method = new KeyValuePair<string, object>(SemanticConventions.AttributeHttpMethod, "GET");
+            var scheme = new KeyValuePair<string, object>(SemanticConventions.AttributeHttpScheme, "http");
+            var statusCode = new KeyValuePair<string, object>(SemanticConventions.AttributeHttpStatusCode, 200);
+            var flavor = new KeyValuePair<string, object>(SemanticConventions.AttributeHttpFlavor, "HTTP/1.1");
+            Assert.Contains(method, metric.Attributes);
+            Assert.Contains(scheme, metric.Attributes);
+            Assert.Contains(statusCode, metric.Attributes);
+            Assert.Contains(flavor, metric.Attributes);
+            Assert.Equal(4, metric.Attributes.Length);
+
+            for (var i = 1; i < requestMetrics.Length; ++i)
+            {
+                metric = requestMetrics[i] as ISumMetric;
+                Assert.NotNull(metric);
+                Assert.Equal(0L, metric.Sum.Value);
+            }
+        }
+
+        public void Dispose()
+        {
+            this.meterProvider?.Dispose();
+        }
+
+        private static void WaitForMetricItems(List<MetricItem> metricItems, int count)
+        {
+            Assert.True(SpinWait.SpinUntil(
+                () =>
+                {
+                    Thread.Sleep(10);
+                    return metricItems.Count >= count;
+                },
+                TimeSpan.FromSeconds(1)));
+        }
+    }
+}

test/OpenTelemetry.Instrumentation.AspNetCore.Tests/OpenTelemetry.Instrumentation.AspNetCore.Tests.csproj

@@ -19,6 +19,7 @@
     <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.Instrumentation.AspNetCore\OpenTelemetry.Instrumentation.AspNetCore.csproj" />
     <Compile Include="$(RepoRoot)\test\OpenTelemetry.Tests\Shared\EventSourceTestHelper.cs" Link="EventSourceTestHelper.cs" />
     <Compile Include="$(RepoRoot)\test\OpenTelemetry.Tests\Shared\TestEventListener.cs" Link="TestEventListener.cs" />
+    <Compile Include="$(RepoRoot)\test\OpenTelemetry.Tests\Shared\TestExporter.cs" Link="TestExporter.cs" />
     <Compile Include="$(RepoRoot)\test\OpenTelemetry.Tests\Shared\InMemoryEventListener.cs" Link="InMemoryEventListener.cs" />
   </ItemGroup>