Delete Account: started adding unit tests

__mocks__/gatsby-plugin-firebase/constants/functions.js

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+const deleteUserFunctionName = 'deleteUser';
+
+const defaultDelayInMilliseconds = 2000;
+
+class Functions {
+  static get deleteUserFunctionName() {
+    return deleteUserFunctionName;
+  }
+
+  static get defaultDelayInMilliseconds() {
+    return defaultDelayInMilliseconds;
+  }
+}
+
+export default Functions;

__mocks__/gatsby-plugin-firebase/functions/functions.js

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+/* eslint-disable no-underscore-dangle */
+import { v4 as uuidv4 } from 'uuid';
+
+import FunctionsConstants from '../constants/functions';
+import HttpsCallableResult from './httpsCallableResult';
+import { delay } from '../../../src/utils/index';
+
+const singleton = Symbol('');
+const singletonEnforcer = Symbol('');
+
+const deleteUser = async () => {
+  await delay(FunctionsConstants.defaultDelayInMilliseconds);
+
+  return new HttpsCallableResult(true);
+};
+
+class Functions {
+  constructor(enforcer) {
+    if (enforcer !== singletonEnforcer) {
+      throw new Error('Cannot construct singleton');
+    }
+
+    this._uuid = uuidv4();
+
+    this._httpsCallables = {};
+    this._httpsCallables[
+      FunctionsConstants.deleteUserFunctionName
+    ] = deleteUser;
+  }
+
+  static get instance() {
+    if (!this[singleton]) {
+      this[singleton] = new Functions(singletonEnforcer);
+    }
+
+    return this[singleton];
+  }
+
+  get uuid() {
+    return this._uuid;
+  }
+
+  httpsCallable(name) {
+    if (!name) {
+      throw new Error('name must be provided.');
+    } else if (typeof name !== 'string') {
+      throw new Error('name should be a string.');
+    }
+
+    return this._httpsCallables[name];
+  }
+}
+
+export default Functions;

__mocks__/gatsby-plugin-firebase/functions/httpsCallableResult.js

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+/* eslint-disable no-underscore-dangle */
+import { v4 as uuidv4 } from 'uuid';
+
+class HttpsCallableResult {
+  constructor(data) {
+    this._uuid = uuidv4();
+    this._data = data;
+  }
+
+  get data() {
+    return this._data;
+  }
+
+  get uuid() {
+    return this._uuid;
+  }
+}
+
+export default HttpsCallableResult;