Add tests and detect WhatsApp Web updates (#686)

* test setup, add initializer tests

* test sending messages

* add script to check latest version

* add github action

* use env vars

* configure environment with .env file

* add test for sticker name and author

* add DownloadManager model

* test chats and contacts

* test for number utility functions

* throw error if no remote id has been set

* Update .version

tests/helper.js

@@ -0,0 +1,40 @@
+const path = require('path');
+const Client = require('../src/Client');
+const Util = require('../src/util/Util');
+
+require('dotenv').config();
+
+const remoteId = process.env.WWEBJS_TEST_REMOTE_ID;
+if(!remoteId) throw new Error('The WWEBJS_TEST_REMOTE_ID environment variable has not been set.');
+
+function getSessionFromEnv() {
+    const envSession = process.env.WWEBJS_TEST_SESSION;
+    if(envSession) return JSON.parse(envSession);
+
+    const envSessionPath = process.env.WWEBJS_TEST_SESSION_PATH;
+    if(envSessionPath) {
+        const absPath = path.resolve(process.cwd(), envSessionPath);
+        return require(absPath);
+    }
+    
+    throw new Error('No session found in environment.');
+}
+
+function createClient({withSession, options: additionalOpts}={}) {
+    const options = {};
+    if(withSession) {
+        options.session = getSessionFromEnv();
+    }
+
+    return new Client(Util.mergeDefault(options, additionalOpts || {}));
+}
+
+function sleep(ms) {
+    return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+module.exports = {
+    sleep, 
+    createClient,
+    remoteId
+};