Get basic test up and passing

This replaces the 'ws' library with built-in websockets so that we can mock a server and successfully connect to it. A simple test verifies that Unit is handling a message request and response as we expect it to.

tests/unit.test.ts

@@ -1,3 +1,45 @@
-describe("empty test", () => {
-  it("passes", () => {});
+import { Unit } from "../src/index";
+import * as messages from "../src/messages/messages";
+import WS from "jest-websocket-mock";
+
+function makeid(length: number) {
+  const characters =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+  const charactersLength = characters.length;
+
+  let result = "";
+  let counter = 0;
+  while (counter < length) {
+    result += characters.charAt(Math.floor(Math.random() * charactersLength));
+    counter += 1;
+  }
+
+  return result;
+}
+
+describe("basic message tests", () => {
+  let unit: Unit;
+  let mockServer: WS;
+  beforeEach(async () => {
+    mockServer = new WS("ws://localhost:6680");
+
+    unit = new Unit("localhost", 6680);
+    await unit.connect();
+    await mockServer.connected;
+  });
+
+  afterEach(async () => {
+    unit.close();
+    WS.clean();
+  });
+
+  it("can send a message and return its response", async () => {
+    const msg = messages.GetBodyStatus();
+    const sender = unit.send(msg);
+    await expect(mockServer).toReceiveMessage(JSON.stringify(msg));
+    const response = { messageID: msg.messageID, command: makeid(8) };
+    mockServer.send(JSON.stringify(response));
+    const clientResp = await sender;
+    expect(clientResp).toEqual(response);
+  });
 });