feat: auto port selection when default port is busy

src/shared/port-utils.test.ts

@@ -0,0 +1,105 @@
+import { describe, it, expect, beforeAll, afterAll } from "bun:test"
+import {
+  isPortAvailable,
+  findAvailablePort,
+  getAvailableServerPort,
+  DEFAULT_SERVER_PORT,
+} from "./port-utils"
+
+describe("port-utils", () => {
+  describe("isPortAvailable", () => {
+    it("#given unused port #when checking availability #then returns true", async () => {
+      const port = 59999
+      const result = await isPortAvailable(port)
+      expect(result).toBe(true)
+    })
+
+    it("#given port in use #when checking availability #then returns false", async () => {
+      const port = 59998
+      const blocker = Bun.serve({
+        port,
+        hostname: "127.0.0.1",
+        fetch: () => new Response("blocked"),
+      })
+
+      try {
+        const result = await isPortAvailable(port)
+        expect(result).toBe(false)
+      } finally {
+        blocker.stop(true)
+      }
+    })
+  })
+
+  describe("findAvailablePort", () => {
+    it("#given start port available #when finding port #then returns start port", async () => {
+      const startPort = 59997
+      const result = await findAvailablePort(startPort)
+      expect(result).toBe(startPort)
+    })
+
+    it("#given start port blocked #when finding port #then returns next available", async () => {
+      const startPort = 59996
+      const blocker = Bun.serve({
+        port: startPort,
+        hostname: "127.0.0.1",
+        fetch: () => new Response("blocked"),
+      })
+
+      try {
+        const result = await findAvailablePort(startPort)
+        expect(result).toBe(startPort + 1)
+      } finally {
+        blocker.stop(true)
+      }
+    })
+
+    it("#given multiple ports blocked #when finding port #then skips all blocked", async () => {
+      const startPort = 59993
+      const blockers = [
+        Bun.serve({ port: startPort, hostname: "127.0.0.1", fetch: () => new Response() }),
+        Bun.serve({ port: startPort + 1, hostname: "127.0.0.1", fetch: () => new Response() }),
+        Bun.serve({ port: startPort + 2, hostname: "127.0.0.1", fetch: () => new Response() }),
+      ]
+
+      try {
+        const result = await findAvailablePort(startPort)
+        expect(result).toBe(startPort + 3)
+      } finally {
+        blockers.forEach((b) => b.stop(true))
+      }
+    })
+  })
+
+  describe("getAvailableServerPort", () => {
+    it("#given preferred port available #when getting port #then returns preferred with wasAutoSelected=false", async () => {
+      const preferredPort = 59990
+      const result = await getAvailableServerPort(preferredPort)
+      expect(result.port).toBe(preferredPort)
+      expect(result.wasAutoSelected).toBe(false)
+    })
+
+    it("#given preferred port blocked #when getting port #then returns alternative with wasAutoSelected=true", async () => {
+      const preferredPort = 59989
+      const blocker = Bun.serve({
+        port: preferredPort,
+        hostname: "127.0.0.1",
+        fetch: () => new Response("blocked"),
+      })
+
+      try {
+        const result = await getAvailableServerPort(preferredPort)
+        expect(result.port).toBeGreaterThan(preferredPort)
+        expect(result.wasAutoSelected).toBe(true)
+      } finally {
+        blocker.stop(true)
+      }
+    })
+  })
+
+  describe("DEFAULT_SERVER_PORT", () => {
+    it("#given constant #when accessed #then returns 4096", () => {
+      expect(DEFAULT_SERVER_PORT).toBe(4096)
+    })
+  })
+})