Test Driven Development with Meteor - SitePoint

Meteor: A JavaScript Framework for Rapid Realtime Web App Development and its Testing Framework, Laika

Meteor has rapidly gained popularity as a JavaScript framework for building real-time single-page web applications. Its speed and ease of use make it attractive for both prototyping and high-volume production apps. However, the absence of a comprehensive, built-in testing framework initially posed a challenge. This article introduces Laika, a solution designed to address this need.

Key Features of Laika

Laika is a robust testing framework specifically built for Meteor applications. Its key strengths include:

• Full-Stack Testing: Laika enables testing of both server-side and client-side code, crucial given Meteor's tightly coupled architecture.
• Multi-Client Support: It allows testing with multiple clients, accurately simulating real-world scenarios involving concurrent users and real-time data updates.
• Isolated Testing Environment: Each test runs in a separate application instance with a clean database, ensuring test isolation and preventing interference between tests. While this enhances accuracy, it can lead to slightly slower test execution.
• Mocha Integration: Laika leverages the popular Mocha JavaScript testing framework, inheriting its features and providing familiarity for developers already using Mocha. It extends Mocha's capabilities to handle Meteor-specific functionalities like real-time data synchronization.

Beyond Prototypes: Testing Production-Ready Meteor Apps

While Meteor's early days focused on rapid prototyping, its capabilities now support large-scale production applications. However, rigorous testing is paramount before deploying such applications. Laika fills this gap by providing a user-friendly and well-documented solution for comprehensive testing.

Setting Up Laika

Before using Laika, ensure you have the following prerequisites installed:

• Node.js
• PhantomJS (for client-side testing)
• MongoDB (Laika requires a separate MongoDB instance for each test)

Remember to run MongoDB with optimizations for Laika using the command: mongod --smallfiles --noprealloc --nojournal

Finally, install Laika globally using: sudo npm install -g laika

Getting Started with Laika: A Practical Example

Let's illustrate Laika's usage with a simple Meteor application that manages a Posts collection. The following demonstrates testing the insertion of a document from a client and its observation on the server:

<code class="language-javascript">var assert = require('assert');

suite('Posts', function() {
  ltest('using both client and the server', function(done, server, client) {
    server.eval(function() {
      Posts.find().observe({
        added: addedNewPost
      });

      function addedNewPost(post) {
        emit('post', post);
      }
    });

    server.once('post', function(post) {
      assert.equal(post.title, 'hello title');
      done();
    });

    client.eval(function() {
      Posts.insert({title: 'hello title'});
    });
  });
});</code>

This code showcases Laika's ability to interact with both the server and client using server.eval() and client.eval(), respectively. The emit() function sends data between the tested code and the test itself.

After creating your tests, navigate to your project directory and run Laika. The output will show the test results.

Laika's Internal Mechanics

Laika employs several techniques to achieve its functionality:

• Isolated Testing: Each test runs in an isolated environment with a fresh database.
• TCP Communication (Server): Laika injects code into the Meteor server and communicates via a TCP connection for code evaluation and result retrieval.
• PhantomJS (Client): Laika utilizes PhantomJS to create headless browser instances for client-side testing.
• Mocha Integration: Laika builds upon the Mocha testing framework.

Error Handling and Synchronous Testing with evalSync()

Laika provides robust error handling, reporting errors encountered during test execution. While it doesn't pinpoint exact line numbers, it identifies the failing test and context. For simpler, synchronous tests, Laika offers the evalSync() method, simplifying the code and avoiding callback hell. However, remember that evalSync() is only available within the main test callback.

Conclusion

Laika offers a powerful and user-friendly solution for testing Meteor applications. Its features, including full-stack testing, multi-client support, and isolated test environments, make it an invaluable tool for developers building robust and reliable Meteor applications. The project is open-source and available on GitHub.

(FAQs section omitted for brevity, as it is largely unrelated to the core functionality of Laika and the provided text.)

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