test: add tests for getPort

Author: adriandlam

packages/core/src/util.test.ts

@@ -343,3 +343,96 @@ describe('parseDurationToDate', () => {
     });
   });
 });
+
+describe('getPort', () => {
+  const createServer = () =>
+    http.createServer((_request, response) => {
+      response.end();
+    });
+
+  const startServer = async (port: number, host = '127.0.0.1') => {
+    const server = createServer().listen(port, host);
+    await new Promise<void>((resolve) => {
+      server.on('listening', resolve);
+    });
+    return server;
+  };
+
+  it('should return undefined when process is not listening on any port', () => {
+    // This test assumes the test process itself isn't listening on any port
+    const port = getPort();
+    expect(port).toBeUndefined();
+  });
+
+  it('should detect port when server is listening', async () => {
+    // Use a high port number to avoid conflicts
+    const testPort = 50000 + Math.floor(Math.random() * 10000);
+    const server = await startServer(testPort);
+
+    // Give the OS a moment to register the port
+    await new Promise((resolve) => setTimeout(resolve, 100));
+
+    const detectedPort = getPort();
+    expect(detectedPort).toBe(testPort);
+
+    server.close();
+  });
+
+  it('should return smallest port when listening on multiple ports', async () => {
+    const port1 = 50000 + Math.floor(Math.random() * 5000);
+    const port2 = port1 + 100;
+    const port3 = port1 + 200;
+
+    const server1 = await startServer(port1);
+    const server2 = await startServer(port2);
+    const server3 = await startServer(port3);
+
+    // Give the OS a moment to register the ports
+    await new Promise((resolve) => setTimeout(resolve, 100));
+
+    const detectedPort = getPort();
+    expect(detectedPort).toBe(port1); // Should return the smallest
+
+    server1.close();
+    server2.close();
+    server3.close();
+  });
+
+  it('should work with IPv6 localhost', async () => {
+    const testPort = 50000 + Math.floor(Math.random() * 10000);
+    let server: http.Server | undefined;
+
+    try {
+      server = await startServer(testPort, '::1');
+
+      // Give the OS a moment to register the port
+      await new Promise((resolve) => setTimeout(resolve, 100));
+
+      const detectedPort = getPort();
+      expect(detectedPort).toBe(testPort);
+    } catch {
+      // IPv6 might not be available on all systems, skip the test
+      if (server) server.close();
+      return;
+    }
+
+    if (server) server.close();
+  });
+
+  it('should handle 0.0.0.0 binding', async () => {
+    const testPort = 50000 + Math.floor(Math.random() * 10000);
+    const server = createServer().listen(testPort, '0.0.0.0');
+
+    await new Promise<void>((resolve) => {
+      server.on('listening', resolve);
+    });
+
+    // Give the OS a moment to register the port
+    await new Promise((resolve) => setTimeout(resolve, 100));
+
+    const detectedPort = getPort();
+    expect(detectedPort).toBe(testPort);
+
+    server.close();
+  });
+});