Lens app source code (#119)

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

spec/src/main/port_spec.ts

@@ -0,0 +1,39 @@
+import { EventEmitter } from 'events'
+
+class MockServer extends EventEmitter {
+  listen = jest.fn((obj) => {
+    if(obj.port < 9003) {
+      this.emit('error', new Error("fail!"))
+    } else {
+      this.emit('listening', {})
+    }
+    return this
+  })
+  unref = jest.fn()
+  close = jest.fn((cb) => {
+    cb()
+  })
+}
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const net = require("net")
+jest.mock("net")
+
+import * as port from "../../../src/main/port"
+
+describe("getFreePort", () => {
+  beforeEach(() => {
+    net.createServer.mockReturnValue(new MockServer)
+  })
+
+  afterEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it("fails for an invalid range", async () => {
+    return expect(port.getFreePort(1, 2)).rejects.toMatch('free port')
+  })
+
+  it("finds the next free port", async () => {
+    return expect(port.getFreePort(9000, 9005)).resolves.toBe(9003)
+  })
+})