Added mocked Mailgun client to browser test env

refs https://github.com/TryGhost/Ghost/pull/15959

- To be able to test and intercept emails we need a mock in test environment - avoids making calls to the Mailgun API

ghost/core/test/e2e-browser/utils/global-setup.js

@@ -64,7 +64,8 @@ const setup = async (playwrightConfig) => {
         await startGhost({
             frontend: true,
             server: true,
-            backend: true
+            backend: true,
+            mockMailgun: true
         });
     }
 

ghost/core/test/utils/e2e-framework.js

@@ -40,6 +40,7 @@ const supertest = require('supertest');
  * @param {Boolean} [options.backend] Boot the backend
  * @param {Boolean} [options.frontend] Boot the frontend
  * @param {Boolean} [options.server] Start a server
+ * @param {Boolean} [options.mockMailgun] Mock mailgun client module
  * @returns {Promise<Express.Application>} ghost
  */
 const startGhost = async (options = {}) => {
@@ -56,13 +57,20 @@ const startGhost = async (options = {}) => {
     const defaults = {
         backend: true,
         frontend: false,
-        server: false
+        server: false,
+        mockMailgun: false
     };
 
     // Ensure the state of all data, including DB and caches
     await resetData();
 
     const bootOptions = Object.assign({}, defaults, options);
+    if (bootOptions.mockMailgun) {
+        const rewire = require('rewire');
+        const bulkEmail = rewire('../../core/server/services/bulk-email');
+        let mockMailgunClient = require('./mocks/MailgunClientMock');
+        bulkEmail.__set__('_mailgunClient', mockMailgunClient);
+    }
 
     const ghostServer = await boot(bootOptions);
 

ghost/core/test/utils/mocks/MailgunClientMock.js

@@ -0,0 +1,27 @@
+const ObjectID = require('bson-objectid').default;
+
+class MockMailgunClient {
+    getInstance() {
+        return {};
+    }
+
+    /**
+     *
+     * @param {Promise<{id}>}
+     */
+    async send() {
+        return {
+            id: `mailgun-mock-id-${ObjectID().toHexString()}`
+        };
+    }
+
+    /**
+     * Act as if always configured on test environment
+     * @returns true
+     */
+    isConfigured() {
+        return true;
+    }
+}
+
+module.exports = new MockMailgunClient();