Firebase mock: added auth to new implementation

__mocks__/__tests__/gatsby-plugin-firebase_2.test.js

@@ -76,6 +76,7 @@ describe('database', () => {
         .ref(`resumes/${FirebaseMock.database().demoResumeId}`)
         .once('value')
     ).val();
+
     expect(resume).toBeTruthy();
     expect(resume.id).toEqual(FirebaseMock.database().demoResumeId);
   });
@@ -87,6 +88,7 @@ describe('database', () => {
     const resume = (
       await FirebaseMock.database().ref(`resumes/${resumeId}`).once('value')
     ).val();
+
     expect(resume).toBeNull();
   });
 
@@ -98,6 +100,7 @@ describe('database', () => {
         .ref(`users/${FirebaseMock.database().testUser.uid}`)
         .once('value')
     ).val();
+
     expect(user).toBeTruthy();
     expect(user.uid).toEqual(FirebaseMock.database().testUser.uid);
   });
@@ -109,6 +112,62 @@ describe('database', () => {
     const user = (
       await FirebaseMock.database().ref(`users/${userId}`).once('value')
     ).val();
+
     expect(user).toBeNull();
   });
 });
+
+describe('auth', () => {
+  beforeEach(() => {
+    FirebaseMock.auth().clearOnAuthStateChangedObservers();
+  });
+
+  it('reuses existing Auth instance', () => {
+    const auth1 = FirebaseMock.auth();
+    const auth2 = FirebaseMock.auth();
+
+    expect(auth1.uuid).toBeTruthy();
+    expect(auth2.uuid).toBeTruthy();
+    expect(auth1.uuid).toEqual(auth2.uuid);
+  });
+
+  it('returns test user when signing in anonymously', async () => {
+    const user = await FirebaseMock.auth().signInAnonymously();
+
+    expect(user).toBeTruthy();
+    expect(user).toEqual(FirebaseMock.database().testUser);
+  });
+
+  it('calls onAuthStateChanged observer with test user when signing in anonymously', async () => {
+    let user = null;
+    let error = null;
+    FirebaseMock.auth().onAuthStateChanged(
+      (_user) => {
+        user = _user;
+      },
+      (_error) => {
+        error = _error;
+      },
+    );
+
+    await FirebaseMock.auth().signInAnonymously();
+
+    expect(user).toBeTruthy();
+    expect(user).toEqual(FirebaseMock.database().testUser);
+    expect(error).toBeNull();
+  });
+
+  it('onAuthStateChanged unsubscribe removes observer', () => {
+    const observer = () => {};
+    const unsubscribe = FirebaseMock.auth().onAuthStateChanged(observer);
+    expect(unsubscribe).toBeTruthy();
+    expect(FirebaseMock.auth().onAuthStateChangedObservers.length).toEqual(1);
+    expect(FirebaseMock.auth().onAuthStateChangedObservers[0]).toEqual(
+      observer,
+    );
+
+    unsubscribe();
+
+    expect(FirebaseMock.auth().onAuthStateChangedObservers.length).toEqual(0);
+  });
+});

__mocks__/gatsby-plugin-firebase_2.js

@@ -2,6 +2,52 @@ import path from 'path';
 import fs from 'fs';
 import { v4 as uuidv4 } from 'uuid';
 
+class Auth {
+  static #instance = undefined;
+  #uuid = '';
+  #onAuthStateChangedObservers = [];
+
+  constructor() {
+    if (Auth.#instance) {
+      return Auth.#instance;
+    }
+
+    Auth.#instance = this;
+
+    this.#uuid = uuidv4();
+  }
+
+  get uuid() {
+    return this.#uuid;
+  }
+
+  get onAuthStateChangedObservers() {
+    return this.#onAuthStateChangedObservers;
+  }
+
+  clearOnAuthStateChangedObservers() {
+    this.#onAuthStateChangedObservers = [];
+  }
+
+  onAuthStateChanged(observer) {
+    this.#onAuthStateChangedObservers.push(observer);
+
+    return () => {
+      this.#onAuthStateChangedObservers = this.#onAuthStateChangedObservers.filter(
+        (observer) => observer !== observer,
+      );
+    };
+  }
+
+  async signInAnonymously() {
+    this.#onAuthStateChangedObservers.forEach((observer) =>
+      observer(Database.testUser),
+    );
+
+    return Promise.resolve(Database.testUser);
+  }
+}
+
 class DataSnapshot {
   #eventType = '';
   #reference = null;
@@ -127,6 +173,11 @@ class Reference {
 }
 
 class Database {
+  static testUser = {
+    email: 'test.user@noemail.com',
+    name: 'Test User',
+    uid: 'testuser123',
+  };
   static resumesPath = 'resumes';
   static usersPath = 'users';
   static #instance = undefined;
@@ -145,11 +196,7 @@ class Database {
   }
 
   get testUser() {
-    return {
-      email: 'test.user@noemail.com',
-      name: 'Test User',
-      uid: 'testuser123',
-    };
+    return Database.testUser;
   }
 
   get demoResumeId() {
@@ -253,6 +300,10 @@ const database = () => {
 */
 
 class FirebaseMock {
+  static auth() {
+    return new Auth();
+  }
+
   static database() {
     return new Database();
   }