Initial WebUSB tests in nodejs mode with webusb providing nodejs based transport

package.json

@@ -71,6 +71,7 @@
   },
   "devDependencies": {
     "canvas": "^2.7.0",
-    "prettier": "^2.2.1"
+    "prettier": "^2.2.1",
+    "webusb": "^2.2.0"
   }
 }

src/device/device.test.ts

@@ -0,0 +1,92 @@
+/**
+ * @jest-environment node
+ *
+ * Without node environment USB code fails with a buffer type check.
+ * It might be we could create a custom environment that was web but
+ * with a tweak to Buffer.
+ */
+import {
+  ConnectionStatus,
+  EVENT_STATUS,
+  MicrobitWebUSBConnection,
+} from "./device";
+import { USB } from "webusb";
+
+const describeDeviceOnly = process.env.TEST_MODE_DEVICE
+  ? describe
+  : describe.skip;
+
+describe("MicrobitWebUSBConnection (WebUSB unsupported)", () => {
+  it("notices if WebUSB isn't supported", () => {
+    (global as any).navigator = {};
+    const microbit = new MicrobitWebUSBConnection();
+    expect(microbit.status).toBe(ConnectionStatus.NOT_SUPPORTED);
+  });
+});
+
+describeDeviceOnly("MicrobitWebUSBConnection (WebUSB supported)", () => {
+  beforeAll(() => {
+    // Maybe we can move this to a custom jest environment?
+    (global as any).navigator = {
+      usb: new USB({}),
+    };
+  });
+
+  it("shows no device as initial status", () => {
+    const microbit = new MicrobitWebUSBConnection();
+    expect(microbit.status).toBe(ConnectionStatus.NO_AUTHORIZED_DEVICE);
+  });
+
+  it("connects and disconnects updating status and events", async () => {
+    const events: ConnectionStatus[] = [];
+    const connection = new MicrobitWebUSBConnection();
+    connection.on(EVENT_STATUS, (status: ConnectionStatus) =>
+      events.push(status)
+    );
+
+    await connection.connect();
+
+    expect(connection.status).toEqual(ConnectionStatus.CONNECTED);
+    expect(events).toEqual([ConnectionStatus.CONNECTED]);
+
+    // without this it breaks! something is up!
+    await new Promise((resolve) => setTimeout(resolve, 100));
+    await connection.disconnect();
+    connection.dispose();
+
+    expect(connection.status).toEqual(ConnectionStatus.NOT_CONNECTED);
+    expect(events).toEqual([
+      ConnectionStatus.CONNECTED,
+      ConnectionStatus.NOT_CONNECTED,
+    ]);
+  });
+
+  it("flashes using partial flashing when possible", async () => {
+    // Flash MakeCode hex that outputs serial.
+    // Flash MicroPython hex that outputs serial.
+    // Flash another MicroPython hex, assert that we got a small number of progress events.
+    // I think we need to rejig the interface to get flash data before writing this.
+  });
+
+  it("connects to flash and stays connected afterwards", () => {
+    // Is this actually sensible?
+  });
+
+  it("fires a serial reset event when stopping serial", () => {});
+
+  it("reinstates serial after flashing", () => {});
+
+  it("serial echo test", async () => {
+    // Flash a hex that echos serial
+    // Use serialWrite to write serial data.
+    // Assert same content is received.
+    // Useful to test unicode?
+  });
+
+  it("notices disconnects and updates status", () => {
+    // Might need a mock-style tests for this.
+  });
+
+  // Is it feasible to test many of the error cases?
+  // I think we'd need to pass a mock DAPWrapper.
+});