added tests to project

CursorLang.Tests/Infrastructure/FakeHttp.cs

@@ -0,0 +1,41 @@
+using System.Net;
+using System.Net.Http;
+using System.Text;
+
+namespace CursorLang.Tests.Infrastructure;
+
+/// <summary>
+/// The network as the test writes it: the answer is decided here rather than
+/// by a repository somewhere.
+/// </summary>
+internal sealed class FakeHttpHandler : HttpMessageHandler
+{
+    private readonly Func<HttpRequestMessage, HttpResponseMessage> _reply;
+
+    internal FakeHttpHandler(Func<HttpRequestMessage, HttpResponseMessage> reply) => _reply = reply;
+
+    internal List<HttpRequestMessage> Requests { get; } = [];
+
+    internal static FakeHttpHandler Json(string json) => new(_ => new HttpResponseMessage(HttpStatusCode.OK)
+    {
+        Content = new StringContent(json, Encoding.UTF8, "application/json"),
+    });
+
+    internal static FakeHttpHandler Status(HttpStatusCode status) =>
+        new(_ => new HttpResponseMessage(status));
+
+    internal static FakeHttpHandler Bytes(byte[] content) => new(_ => new HttpResponseMessage(HttpStatusCode.OK)
+    {
+        Content = new ByteArrayContent(content),
+    });
+
+    internal HttpClient CreateClient() => new(this);
+
+    protected override Task<HttpResponseMessage> SendAsync(
+        HttpRequestMessage request,
+        CancellationToken cancellationToken)
+    {
+        Requests.Add(request);
+        return Task.FromResult(_reply(request));
+    }
+}