Adds basic TestableHttpMessageHandler.

Author: dnperfors

src/HttpClientTestHelpers/TestableHttpMessageHandler.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace HttpClientTestHelpers
+{
+    /// <summary>
+    /// A testable HTTP message handler that captures all requests and always returns the same response.
+    /// </summary>
+    public class TestableHttpMessageHandler : HttpMessageHandler
+    {
+        private readonly ConcurrentQueue<HttpRequestMessage> httpRequestMessages = new ConcurrentQueue<HttpRequestMessage>();
+        private HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
+
+        /// <summary>
+        /// Gets the collection of captured requests made using this HttpMessageHandler.
+        /// </summary>
+        public IEnumerable<HttpRequestMessage> Requests => httpRequestMessages;
+
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            httpRequestMessages.Enqueue(request);
+            return Task.FromResult(response);
+        }
+
+        /// <summary>
+        /// Configure the <see cref="HttpResponseMessage"/> that should be returned for each request.
+        /// </summary>
+        /// <param name="httpResponseMessage"></param>
+        public void RespondWith(HttpResponseMessage httpResponseMessage)
+        {
+            response = httpResponseMessage ?? throw new ArgumentNullException(nameof(httpResponseMessage));
+        }
+    }
+}

test/HttpClientTestHelpers.Tests/.editorconfig

@@ -1,3 +1,6 @@
 [*.cs]
 # CA1707: Identifiers should not contain underscores
 dotnet_diagnostic.CA1707.severity = none
+
+# CA2007: Consider calling ConfigureAwait on the awaited task
+dotnet_diagnostic.CA2007.severity = silent

test/HttpClientTestHelpers.Tests/TestableHttpMessageHandlerTests.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Net;
+using System.Net.Http;
+using System.Threading.Tasks;
+
+using Xunit;
+
+namespace HttpClientTestHelpers.Tests
+{
+    public class TestableHttpMessageHandlerTests
+    {
+        [Fact]
+        public async Task SendAsync_WhenRequestsAreMade_LogsRequests()
+        {
+            using var sut = new TestableHttpMessageHandler();
+            using var client = new HttpClient(sut);
+            using var request = new HttpRequestMessage(HttpMethod.Get, "https://example.com");
+
+            _ = await client.SendAsync(request);
+
+            Assert.Contains(request, sut.Requests);
+        }
+
+        [Fact]
+        public async Task SendAsync_WhenMultipleRequestsAreMade_AllRequestsAreLogged()
+        {
+            using var sut = new TestableHttpMessageHandler();
+            using var client = new HttpClient(sut);
+            using var request1 = new HttpRequestMessage(HttpMethod.Get, "https://example1.com");
+            using var request2 = new HttpRequestMessage(HttpMethod.Post, "https://example2.com");
+            using var request3 = new HttpRequestMessage(HttpMethod.Delete, "https://example3.com");
+            using var request4 = new HttpRequestMessage(HttpMethod.Head, "https://example4.com");
+
+            _ = await client.SendAsync(request1);
+            _ = await client.SendAsync(request2);
+            _ = await client.SendAsync(request3);
+            _ = await client.SendAsync(request4);
+
+            Assert.Equal(new[] { request1, request2, request3, request4 }, sut.Requests);
+        }
+
+        [Fact]
+        public async Task SendAsync_ByDefault_ReturnsHttpStatusCodeOK()
+        {
+            using var sut = new TestableHttpMessageHandler();
+            using var client = new HttpClient(sut);
+
+            var result = await client.GetAsync(new Uri("https://example.com"));
+
+            Assert.Equal(HttpStatusCode.OK, result.StatusCode);
+        }
+
+        [Fact]
+        public async Task SendAsync_WhenRespondWithIsSet_SetRespondIsUsed()
+        {
+            using var sut = new TestableHttpMessageHandler();
+            using var response = new HttpResponseMessage(HttpStatusCode.NotFound);
+            sut.RespondWith(response);
+            using var client = new HttpClient(sut);
+
+            var result = await client.GetAsync(new Uri("https://example.com"));
+
+            Assert.Equal(HttpStatusCode.NotFound, result.StatusCode);
+            Assert.Same(response, result);
+        }
+
+#nullable disable
+        [Fact]
+        public void RespondWith_NullValue_ThrowsArgumentNullException()
+        {
+            using var sut = new TestableHttpMessageHandler();
+            var exception = Assert.Throws<ArgumentNullException>(() => sut.RespondWith(null));
+            Assert.Equal("httpResponseMessage", exception.ParamName);
+        }
+#nullable restore
+    }
+}