fix: show why a client tunnel failed to start (Plugin-Tunnels#2)

src/backend/tests/electron/c2s-runtime.test.ts

@@ -145,6 +145,35 @@ describe("client tunnel runtime authentication", () => {
     expect(sockets).toHaveLength(1);
   });
 
+  it("keeps the relay's reason when it closes after an error", async () => {
+    const { context, runtimes, sockets } = setup();
+    const runtime = { status: { connected: true } };
+    runtimes.set("web", runtime);
+    const test = context.testC2SRelay(
+      { name: "web" },
+      "127.0.0.1",
+      8443,
+      null,
+      runtime,
+    );
+    await vi.waitFor(() => expect(sockets).toHaveLength(1));
+    sockets[0].emit(
+      "message",
+      Buffer.from(
+        JSON.stringify({
+          type: "error",
+          error: "Target 127.0.0.1:8443 refused",
+        }),
+      ),
+      false,
+    );
+    sockets[0].close();
+    expect(await test).toMatchObject({ success: false });
+    expect(runtimes.get("web").status.reason).toBe(
+      "Target 127.0.0.1:8443 refused",
+    );
+  });
+
   it("keeps the tunnel connected when one of its connections fails", async () => {
     const { context, runtimes, sockets } = setup();
     runtimes.set("web", { status: { connected: true, status: "CONNECTED" } });