tests: add UI smoke test for custom slash commands

Author: ammar-agent

tests/ui/slashCommands.integration.test.ts

@@ -0,0 +1,54 @@
+/**
+ * UI smoke test for custom executable slash commands (.mux/commands/*).
+ *
+ * This test uses the mock AI router (via createAppHarness) to avoid calling real LLMs.
+ * It validates the end-to-end UI flow:
+ * - User sends `/<name>`
+ * - mux discovers and runs `.mux/commands/<name>` in the workspace
+ * - stdout becomes the user message sent to the model
+ */
+
+import * as fs from "fs/promises";
+import * as path from "path";
+
+import { preloadTestModules } from "../ipc/setup";
+
+import { createAppHarness } from "./harness";
+
+async function createCustomCommand(options: {
+  workspacePath: string;
+  name: string;
+  script: string;
+}): Promise<void> {
+  const commandsDir = path.join(options.workspacePath, ".mux", "commands");
+  await fs.mkdir(commandsDir, { recursive: true });
+
+  const commandPath = path.join(commandsDir, options.name);
+  await fs.writeFile(commandPath, options.script);
+  await fs.chmod(commandPath, 0o755);
+}
+
+describe("Custom Slash Commands UI (mock router)", () => {
+  beforeAll(async () => {
+    await preloadTestModules();
+  });
+
+  test("runs a custom command and sends stdout as the message", async () => {
+    const app = await createAppHarness({ branchPrefix: "slash-ui" });
+
+    try {
+      await createCustomCommand({
+        workspacePath: app.metadata.namedWorkspacePath,
+        name: "hello",
+        script: '#!/usr/bin/env bash\necho "Hello from custom command"',
+      });
+
+      await app.chat.send("/hello");
+
+      // The command output should become the user message sent to the model.
+      await app.chat.expectTranscriptContains("Mock response: Hello from custom command");
+    } finally {
+      await app.dispose();
+    }
+  }, 60_000);
+});