Add test

Author: tmat

test/TestAssets/TestProjects/WatchHotReloadApp/Program.cs

@@ -8,6 +8,7 @@
 using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
+using System.Runtime.InteropServices;
 
 // <metadata update handler placeholder>
 

test/dotnet-watch.Tests/HotReload/ApplyDeltaTests.cs

@@ -721,6 +721,8 @@ class AppUpdateHandler
         [PlatformSpecificFact(TestPlatforms.Windows)]
         public async Task GracefulTermination_Windows()
         {
+            var tfm = ToolsetInfo.CurrentTargetFramework;
+
             var testAsset = TestAssets.CopyTestAsset("WatchHotReloadApp")
                .WithSource();
 
@@ -739,7 +741,7 @@ public async Task GracefulTermination_Windows()
 
             await App.WaitForOutputLineContaining(MessageDescriptor.WaitingForChanges);
 
-            await App.WaitUntilOutputContains(new Regex(@"dotnet watch 🕵️ \[.*\] Windows Ctrl\+C handling enabled."));
+            await App.WaitUntilOutputContains($"dotnet watch 🕵️ [WatchHotReloadApp ({tfm})] Windows Ctrl+C handling enabled.");
 
             await App.WaitUntilOutputContains("Started");
 
@@ -749,6 +751,37 @@ public async Task GracefulTermination_Windows()
             await App.WaitUntilOutputContains("exited with exit code 0.");
         }
 
+        [PlatformSpecificFact(TestPlatforms.AnyUnix)]
+        public async Task GracefulTermination_Unix()
+        {
+            var tfm = ToolsetInfo.CurrentTargetFramework;
+
+            var testAsset = TestAssets.CopyTestAsset("WatchHotReloadApp")
+               .WithSource();
+
+            var programPath = Path.Combine(testAsset.Path, "Program.cs");
+
+            UpdateSourceFile(programPath, src => src.Replace("// <metadata update handler placeholder>", """
+                using var termSignalRegistration = PosixSignalRegistration.Create(PosixSignal.SIGTERM, _ =>
+                {
+                    Console.WriteLine("SIGTERM detected! Performing cleanup...");
+                });
+                """));
+
+            App.Start(testAsset, [], testFlags: TestFlags.ReadKeyFromStdin);
+
+            await App.WaitForOutputLineContaining(MessageDescriptor.WaitingForChanges);
+
+            await App.WaitUntilOutputContains($"dotnet watch 🕵️ [WatchHotReloadApp ({tfm})] Posix signal handlers registered.");
+
+            await App.WaitUntilOutputContains("Started");
+
+            App.SendControlC();
+
+            await App.WaitForOutputLineContaining("SIGTERM detected! Performing cleanup...");
+            await App.WaitUntilOutputContains("exited with exit code 0.");
+        }
+
         [PlatformSpecificTheory(TestPlatforms.Windows, Skip = "https://github.com/dotnet/sdk/issues/49928")] // https://github.com/dotnet/sdk/issues/49307
         [CombinatorialData]
         public async Task BlazorWasm(bool projectSpecifiesCapabilities)