Running end-to-end tests for Dockerized Javascript applications

21 Sep 2023

docker

End-to-end (E2E) testing is crucial to ensure that your Dockerized JavaScript application functions as intended. In this blog post, we will explore the steps to set up and run E2E tests for your Dockerized JavaScript applications.

Prerequisites

Before we dive into the steps, make sure you have the following prerequisites in place:

Node.js and NPM installed on your machine
Docker installed and running

Step 1: Set up your E2E Testing Framework

To perform E2E testing, you will need a testing framework. One popular choice is Cypress, which provides a simple and powerful way to test your JavaScript applications.

To set up Cypress, open your terminal and navigate to your project directory. Run the following command to install Cypress as a development dependency:

npm install cypress --save-dev

Step 2: Configure Cypress for Docker

By default, Cypress is not able to run tests inside a Docker container. To address this, you need to make a small configuration adjustment.

Create a new file called cypress.json in your project’s root directory. Add the following content to the file:

{
  "browser": "chrome",
  "chromeWebSecurity": false
}

This configuration allows Cypress to use Chrome as the browser and disable web security, which is necessary when running tests inside a Docker container.

Step 3: Write your E2E Tests

With Cypress set up and configured, it’s time to write your E2E tests. Cypress offers a rich set of APIs and utilities to interact with elements, simulate user actions, and assert expected outcomes.

Create a new directory called cypress inside your project’s root directory. Within the cypress directory, create another directory called integration. This is where your test files will reside.

Inside the integration directory, create a new JavaScript file, e.g., example.spec.js. In this file, you can write your test cases using Cypress’s API.

Here’s an example E2E test using Cypress:

describe('Example Test', () => {
  it('Visits the homepage and asserts the title', () => {
    cy.visit('/');
    cy.title().should('eq', 'My Application');
  });
});

Step 4: Dockerize your JavaScript Application

To run your application and E2E tests inside a Docker container, you need to create a Dockerfile. This file specifies the base image, application dependencies, and commands to run.

Create a new file called Dockerfile in your project’s root directory. Add the following content to the file:

# Use a lightweight Node.js image
FROM node:alpine

# Set the working directory
WORKDIR /app

# Copy the package.json and package-lock.json files
COPY package*.json ./

# Install application dependencies
RUN npm install

# Copy the application code
COPY . .

# Expose a port (if necessary)
# EXPOSE 3000

# Run the E2E tests
CMD ["npm", "run", "e2e"]

Ensure that your application code and E2E tests are present in the same directory as the Dockerfile.

Step 5: Build and Run your Docker Container

With the Dockerfile in place, it’s now time to build and run your Docker container.

Open your terminal and navigate to your project’s root directory. Run the following command to build the Docker container:

docker build -t my-app .

Once the container is built, you can execute the following command to run the E2E tests:

docker run -it my-app

Conclusion

In this blog post, we have explored the steps to set up and run end-to-end tests for Dockerized JavaScript applications. With the right framework and proper configuration, you can ensure the robustness and reliability of your applications in a Dockerized environment.

#javascript #docker