Desktop: keep a vault-visibility failure from closing the app, and leave a crash log when anything else does

tests/DodoSSH.Client.App.Tests/CrashLogTests.cs

@@ -0,0 +1,41 @@
+using DodoSSH.Client.App.Platform;
+using DodoSSH.Client.Session;
+
+namespace DodoSSH.Client.App.Tests;
+
+/// <summary>
+/// That the application leaves a record of why it died.
+/// </summary>
+/// <remarks>
+/// An exception nothing caught used to close the window and leave nothing at all behind. Installing the hooks
+/// here also installs them in the test process, which is harmless: they only write to this test's own
+/// directory, and only when something reaches the top.
+/// </remarks>
+public sealed class CrashLogTests : IDisposable
+{
+    private readonly string directory =
+        Path.Combine(Path.GetTempPath(), $"dodossh-crash-{Guid.CreateVersion7():N}");
+
+    public void Dispose()
+    {
+        if (Directory.Exists(directory))
+        {
+            Directory.Delete(directory, recursive: true);
+        }
+    }
+
+    [Fact]
+    public void AnExceptionThatReachesTheTop_IsWrittenToTheProfile()
+    {
+        var paths = new ClientPaths(directory);
+
+        CrashLog.Install(paths);
+        CrashLog.Write("UI thread", new InvalidOperationException("the thing nobody caught"));
+
+        var written = File.ReadAllText(paths.CrashLogFile);
+
+        written.ShouldContain("UI thread");
+        written.ShouldContain("the thing nobody caught");
+        written.ShouldContain(nameof(InvalidOperationException));
+    }
+}