Added Jest for testing both front and backend

server/presenters/__snapshots__/user.test.js.snap

@@ -0,0 +1,8 @@
+exports[`test presents a user 1`] = `
+Object {
+  "avatarUrl": "http://example.com/avatar.png",
+  "id": "123",
+  "name": "Test User",
+  "username": "testuser"
+}
+`;

server/presenters/user.js

@@ -0,0 +1,15 @@
+const presentUser = (ctx, user) => {
+  ctx.cache.set(user.id, user);
+
+  return new Promise(async (resolve, _reject) => {
+    const data = {
+      id: user.id,
+      name: user.name,
+      username: user.username,
+      avatarUrl: user.slackData.image_192,
+    };
+    resolve(data);
+  });
+};
+
+export default presentUser;

server/presenters/user.test.js

@@ -0,0 +1,19 @@
+import presentUser from './user';
+
+import ctx from '../../__mocks__/ctx';
+
+it('presents a user', async () => {
+  const user = await presentUser(
+    ctx,
+    {
+      id: '123',
+      name: 'Test User',
+      username: 'testuser',
+      slackData: {
+        image_192: 'http://example.com/avatar.png',
+      },
+    },
+  );
+
+  expect(user).toMatchSnapshot();
+});