Report a simulator that crashes or closes right after the start

The exit code, read with its signal or NTSTATUS, and the last lines of the
error stream - or of log.txt when it stayed silent. The stream is captured
only while the starter stays to read it.

StarterNG.Tests/SimulatorExitTests.cs

@@ -0,0 +1,65 @@
+using StarterNG.Application;
+using StarterNG.Infrastructure.Adapters;
+using StarterNG.Tests.Fakes;
+
+namespace StarterNG.Tests;
+
+public class SimulatorExitTests
+{
+    private static readonly TimeSpan Session = TimeSpan.FromMinutes(20);
+
+    [Fact]
+    public void A_session_ended_cleanly_is_no_failure()
+    {
+        Assert.False(new SimulatorExit(0, Session, []).Failed);
+    }
+
+    [Fact]
+    public void An_error_code_is_a_failure()
+    {
+        Assert.True(new SimulatorExit(1, Session, []).Failed);
+    }
+
+    [Fact]
+    public void A_window_that_only_flashed_is_a_failure_even_with_a_clean_code()
+    {
+        var exit = new SimulatorExit(0, TimeSpan.FromSeconds(0.2), []);
+
+        Assert.True(exit.Failed);
+        Assert.True(exit.Quick);
+    }
+
+    [Theory]
+    [InlineData(139, "139 (SIGSEGV)")]
+    [InlineData(134, "134 (SIGABRT)")]
+    [InlineData(-1073741819, "0xC0000005 (access violation)")]
+    [InlineData(3, "3")]
+    public void The_code_says_what_killed_it(int code, string described)
+    {
+        Assert.Equal(described, new SimulatorExit(code, Session, []).DescribeCode());
+    }
+
+    [Fact]
+    public void Colour_codes_and_blank_lines_are_dropped_from_the_errors()
+    {
+        var exit = new SimulatorExit(1, Session, ["\u001b[31mBad file: texture\u001b[0m", "", "   "]);
+
+        Assert.Equal(["Bad file: texture"], exit.CleanErrors);
+    }
+
+    [Fact]
+    public async Task A_real_process_leaves_its_exit_code_and_error_stream()
+    {
+        var launcher = new SystemProcessLauncher(new TestInstallation().Log);
+        var (shell, script) = OperatingSystem.IsWindows()
+            ? ("cmd", new[] { "/c", "echo boom 1>&2 & exit 3" })
+            : ("/bin/sh", new[] { "-c", "echo boom >&2; exit 3" });
+
+        var process = launcher.Start(shell, script, null, captureErrors: true, out string? error);
+        Assert.Null(error);
+        await process!.WaitForExitAsync();
+
+        Assert.Equal(3, process.ExitCode);
+        Assert.Equal("boom", Assert.Single(process.ErrorTail).Trim());
+    }
+}

StarterNG.Tests/StartSimulationTests.cs

@@ -54,6 +54,30 @@ public class StartSimulationTests
         Assert.Equal(installation.Paths.Root, launcher.WorkingDirectory);
     }
 
+    [Fact]
+    public void The_error_stream_is_kept_only_while_the_starter_stays_to_read_it()
+    {
+        var (start, launcher, installation) = Rig(files => files.WithExecutable(Build));
+
+        start.Execute(freeFly: true, saveSettings: false);
+        Assert.True(launcher.CapturedErrors);
+
+        // Closing right after the launch would leave the pipe with no reader.
+        installation.SettingsStore.Settings.AutoCloseStarter = true;
+        start.Execute(freeFly: true, saveSettings: false);
+        Assert.False(launcher.CapturedErrors);
+    }
+
+    [Fact]
+    public void The_end_of_the_simulator_log_is_read_for_a_silent_crash()
+    {
+        var (start, _, _) = Rig(files => files
+            .WithExecutable(Build)
+            .WithFile(TestInstallation.At("log.txt"), "first\r\nsecond\r\n\r\nthird\r\n"));
+
+        Assert.Equal(new[] { "second", "third" }, start.SimulatorLogTail(2));
+    }
+
     [Fact]
     public void A_file_that_cannot_be_run_is_not()
     {
@@ -102,10 +126,13 @@ public class StartSimulationTests
 
         public IReadOnlyList<string>? Arguments { get; private set; }
 
+        public bool? CapturedErrors { get; private set; }
+
         public IProcessHandle? Start(string executablePath, IReadOnlyList<string> arguments, string? workingDirectory,
-                                     out string? error)
+                                     bool captureErrors, out string? error)
         {
             Executable = executablePath;
+            CapturedErrors = captureErrors;
             Arguments = arguments;
             WorkingDirectory = workingDirectory;
             error = null;
@@ -121,6 +148,10 @@ public class StartSimulationTests
     {
         public bool HasExited => false;
 
+        public int? ExitCode => null;
+
+        public IReadOnlyList<string> ErrorTail => Array.Empty<string>();
+
         public Task WaitForExitAsync(CancellationToken cancellationToken = default) => Task.CompletedTask;
     }
 }