diff --git a/tests/backend/common.js b/tests/backend/common.js
new file mode 100644
index 000000000..666d69eca
--- /dev/null
+++ b/tests/backend/common.js
@@ -0,0 +1,43 @@
+function m(mod) { return __dirname + '/../../src/' + mod; }
+
+const log4js = require(m('node_modules/log4js'));
+const server = require(m('node/server'));
+const settings = require(m('node/utils/Settings'));
+const supertest = require(m('node_modules/supertest'));
+const webaccess = require(m('node/hooks/express/webaccess'));
+
+const backups = {};
+let inited = false;
+
+exports.agent = null;
+exports.baseUrl = null;
+exports.httpServer = null;
+exports.logger = log4js.getLogger('test');
+
+exports.init = async function() {
+  if (inited) return exports.agent;
+  inited = true;
+
+  // Note: This is only a shallow backup.
+  backups.settings = Object.assign({}, settings);
+  // Start the Etherpad server on a random unused port.
+  settings.port = 0;
+  settings.ip = 'localhost';
+  exports.httpServer = await server.start();
+  exports.baseUrl = `http://localhost:${exports.httpServer.address().port}`;
+  exports.logger.debug(`HTTP server at ${exports.baseUrl}`);
+  // Create a supertest user agent for the HTTP server.
+  exports.agent = supertest(exports.baseUrl);
+  // Speed up authn tests.
+  backups.authnFailureDelayMs = webaccess.authnFailureDelayMs;
+  webaccess.authnFailureDelayMs = 0;
+
+  after(async function() {
+    webaccess.authnFailureDelayMs = backups.authnFailureDelayMs;
+    await server.stop();
+    // Note: This does not unset settings that were added.
+    Object.assign(settings, backups.settings);
+  });
+
+  return exports.agent;
+};
diff --git a/tests/backend/specs/socketio.js b/tests/backend/specs/socketio.js
index 6a4541d74..e17af09fc 100644
--- a/tests/backend/specs/socketio.js
+++ b/tests/backend/specs/socketio.js
@@ -1,36 +1,17 @@
 function m(mod) { return __dirname + '/../../../src/' + mod; }
 
 const assert = require('assert').strict;
+const common = require('../common');
 const io = require(m('node_modules/socket.io-client'));
-const log4js = require(m('node_modules/log4js'));
 const padManager = require(m('node/db/PadManager'));
 const plugins = require(m('static/js/pluginfw/plugin_defs'));
-const server = require(m('node/server'));
 const setCookieParser = require(m('node_modules/set-cookie-parser'));
 const settings = require(m('node/utils/Settings'));
-const supertest = require(m('node_modules/supertest'));
-const webaccess = require(m('node/hooks/express/webaccess'));
 
-const logger = log4js.getLogger('test');
+const logger = common.logger;
 let agent;
-let baseUrl;
-let authnFailureDelayMsBackup;
 
-before(async function() {
-  authnFailureDelayMsBackup = webaccess.authnFailureDelayMs;
-  webaccess.authnFailureDelayMs = 0; // Speed up tests.
-  settings.port = 0;
-  settings.ip = 'localhost';
-  const httpServer = await server.start();
-  baseUrl = `http://localhost:${httpServer.address().port}`;
-  logger.debug(`HTTP server at ${baseUrl}`);
-  agent = supertest(baseUrl);
-});
-
-after(async function() {
-  webaccess.authnFailureDelayMs = authnFailureDelayMsBackup;
-  await server.stop();
-});
+before(async function() { agent = await common.init(); });
 
 // Waits for and returns the next named socket.io event. Rejects if there is any error while waiting
 // (unless waiting for that error event).
@@ -75,7 +56,7 @@ const connect = async (res) => {
   }).join('; ');
 
   logger.debug('socket.io connecting...');
-  const socket = io(`${baseUrl}/`, {
+  const socket = io(`${common.baseUrl}/`, {
     forceNew: true, // Different tests will have different query parameters.
     path: '/socket.io',
     // socketio.js-client on node.js doesn't support cookies (see https://git.io/JU8u9), so the
diff --git a/tests/backend/specs/webaccess.js b/tests/backend/specs/webaccess.js
index 7bce670c4..68d98a7c5 100644
--- a/tests/backend/specs/webaccess.js
+++ b/tests/backend/specs/webaccess.js
@@ -1,32 +1,13 @@
 function m(mod) { return __dirname + '/../../../src/' + mod; }
 
 const assert = require('assert').strict;
-const log4js = require(m('node_modules/log4js'));
+const common = require('../common');
 const plugins = require(m('static/js/pluginfw/plugin_defs'));
-const server = require(m('node/server'));
 const settings = require(m('node/utils/Settings'));
-const supertest = require(m('node_modules/supertest'));
-const webaccess = require(m('node/hooks/express/webaccess'));
 
 let agent;
-const logger = log4js.getLogger('test');
-let authnFailureDelayMsBackup;
 
-before(async function() {
-  authnFailureDelayMsBackup = webaccess.authnFailureDelayMs;
-  webaccess.authnFailureDelayMs = 0; // Speed up tests.
-  settings.port = 0;
-  settings.ip = 'localhost';
-  const httpServer = await server.start();
-  const baseUrl = `http://localhost:${httpServer.address().port}`;
-  logger.debug(`HTTP server at ${baseUrl}`);
-  agent = supertest(baseUrl);
-});
-
-after(async function() {
-  webaccess.authnFailureDelayMs = authnFailureDelayMsBackup;
-  await server.stop();
-});
+before(async function() { agent = await common.init(); });
 
 describe('webaccess: without plugins', function() {
   const backup = {};