Showed the Rust compiler actually used on the information page (#1160)

app/Tests/Tools/RuntimeInfoResponseTests.cs

@@ -0,0 +1,40 @@
+using System.Text.Json;
+
+using AIStudio.Tools.Rust;
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks that the app reads what the runtime tells about itself, the Rust compiler which built it among it.
+/// </summary>
+/// <remarks>
+/// RuntimeInfo in runtime/src/environment.rs names its fields in snake case, and the information page shows
+/// the Rust compiler from it. A name which the app spelled differently would leave the page saying "unknown"
+/// without failing anywhere. The app asks for this answer while it starts, so an answer without the compiler,
+/// as a runtime older than the app sends it, must not fail either. The answers are read with the options of
+/// RustService itself.
+/// </remarks>
+[TestFixture]
+public sealed class RuntimeInfoResponseTests
+{
+    [Test]
+    public void TheAppReadsTheRustCompilerWhichBuiltTheRuntime()
+    {
+        var response = JsonSerializer.Deserialize<RuntimeInfoResponse>("""{"working_directory":"/samples/work","executable_path":"/samples/app/mindwork-ai-studio","linux_package_type":"Flatpak","installation_kind":"User","rust_version":"1.98.1 (commit a1b2c3d4e)"}""", RustService.JSON_OPTIONS);
+
+        Assert.That(response, Is.EqualTo(new RuntimeInfoResponse("/samples/work", "/samples/app/mindwork-ai-studio", LinuxPackageType.FLATPAK, InstallationKind.USER, "1.98.1 (commit a1b2c3d4e)")));
+    }
+
+    [Test]
+    public void ARuntimeOlderThanTheAppNamesNoRustCompiler()
+    {
+        var response = JsonSerializer.Deserialize<RuntimeInfoResponse>("""{"working_directory":"/samples/work","executable_path":"/samples/app/mindwork-ai-studio","linux_package_type":"NotApplicable","installation_kind":"Development"}""", RustService.JSON_OPTIONS);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(response.InstallationKind, Is.EqualTo(InstallationKind.DEVELOPMENT));
+            Assert.That(response.RustVersion, Is.Null);
+        }
+    }
+}