Fixing EnvironmentTypes.TEST Is Undefined In Jest Tests

Hey everyone! Today, we're diving deep into a peculiar issue some of us have encountered while running Jest tests in our frontend projects, specifically within the Open edX environment. It revolves around a TypeError where EnvironmentTypes.TEST comes up as undefined, causing our tests to fail right when they're trying to load modules. This issue isn't consistent across all tests, making it even more of a head-scratcher. Let's break down what's happening and how we can tackle it.

Understanding the Problem

So, what's the deal with this TypeError: Cannot read properties of undefined (reading 'TEST')? It usually pops up in our test configuration files, like site.config.test.tsx. The error message tells us that we're trying to access the TEST property of an EnvironmentTypes object, but for some reason, it's coming back as undefined during the Jest test run. Check the below code:

TypeError: Cannot read properties of undefined (reading 'TEST')

       9 |   logoutUrl: 'http://localhost:8000/logout',
    > 10 |   environment: EnvironmentTypes.TEST,

This typically happens because the site.config.test.tsx file is trying to use EnvironmentTypes.TEST before the module that defines EnvironmentTypes has been properly loaded and initialized by Jest. It’s like trying to use a tool before it’s even been taken out of the box!

This problem was notably observed during the conversion of frontend-app-account to frontend-base and while creating the new MFE for the instructor dashboard. It’s a sneaky issue that can creep into our projects during significant architectural changes or when setting up new modules.

Why Does This Happen?

To really get to the bottom of this, let's explore some of the potential causes:

• Configuration File Problem: The most common culprit is that our site.config.test.tsx file is trying to access EnvironmentTypes.TEST, but during the Jest execution, the EnvironmentTypes object is either undefined or hasn't been properly loaded from the @openedx/frontend-base package. This could be due to incorrect import paths, circular dependencies, or other configuration mishaps.
• Module Loading Order: Jest has its own way of loading modules, and sometimes the order in which it does this can cause issues. If EnvironmentTypes hasn't been exported or isn't available when the config file tries to use it, we'll run into this error. This is often related to how modules are imported and the order in which Jest processes them.

Diving Deeper: Potential Causes and Solutions

To effectively resolve this issue, we need to consider a few key factors and explore potential solutions. Let's break it down:

1. Configuration File Issues

It's possible that the site.config.test.tsx file isn't correctly importing or accessing EnvironmentTypes. To fix this, ensure that the import paths are accurate and that there are no typos. Verify that the @openedx/frontend-base package is correctly installed and that the EnvironmentTypes export is indeed available. Sometimes, a simple reinstallation of the package can resolve underlying issues.

2. Module Loading Order

Jest's module loading order can sometimes cause headaches. To address this, ensure that EnvironmentTypes is exported and available before site.config.test.tsx tries to use it. You can use Jest's setupFiles or setupFilesAfterEnv configuration options to ensure that certain modules are loaded before others. This can help guarantee that EnvironmentTypes is available when site.config.test.tsx needs it.

3. Circular Dependencies

Circular dependencies can lead to unpredictable loading behavior. Check your project for any circular dependencies involving EnvironmentTypes or site.config.test.tsx. Tools like madge can help detect circular dependencies in your codebase. Once identified, refactor your code to eliminate these dependencies, ensuring a clear and linear module loading order.

4. Jest Configuration

Review your Jest configuration file (jest.config.js or similar) to ensure that it is correctly set up to handle the @openedx/frontend-base package. Check the moduleNameMapper and transform options to ensure that Jest knows how to handle the modules in your project. Incorrect configurations can prevent Jest from correctly loading modules, leading to the TypeError.

Quick Fix vs. Long-Term Solution

While a workaround like environment: EnvironmentTypes.TEST ?? 'test' can temporarily solve the issue, it's essential to understand why this is happening and address the root cause. Relying on a workaround without investigating the underlying problem can lead to more significant issues down the line.

The suggested workaround of using the nullish coalescing operator (??) provides a default value when EnvironmentTypes.TEST is undefined. This prevents the TypeError and allows the tests to run. However, it's crucial to recognize that this is merely a temporary fix.

Long-Term Strategies

To truly resolve this issue, follow these steps:

1. Inspect the Module Loading Order: Use Jest's debugging tools to trace the order in which modules are loaded. This can help identify when EnvironmentTypes is being loaded and whether it's available before site.config.test.tsx tries to access it.
2. Refactor Dependencies: If you find that site.config.test.tsx is being loaded before EnvironmentTypes, refactor your dependencies to ensure that EnvironmentTypes is loaded first. This might involve moving import statements or restructuring your module exports.
3. Update Jest Configuration: Ensure that your Jest configuration is correctly set up to handle the @openedx/frontend-base package. Verify that the moduleNameMapper and transform options are correctly configured.

Practical Example

Let's walk through a practical example to illustrate how to resolve this issue. Suppose your jest.config.js file looks like this:

module.exports = {
  // ... other configurations
  moduleNameMapper: {
    '^@openedx/frontend-base(.*){{content}}#39;: '<rootDir>/node_modules/@openedx/frontend-base/$1',
  },
};

Ensure that the moduleNameMapper correctly points to the @openedx/frontend-base package in your node_modules directory. If it doesn't, update the path accordingly.

Additionally, ensure that your site.config.test.tsx file imports EnvironmentTypes correctly:

import { EnvironmentTypes } from '@openedx/frontend-base';

const siteConfig = {
  logoutUrl: 'http://localhost:8000/logout',
  environment: EnvironmentTypes.TEST,
};

export default siteConfig;

If the import path is incorrect, update it to match the correct location of EnvironmentTypes in the @openedx/frontend-base package.

Conclusion

Encountering TypeError: undefined EnvironmentTypes.TEST during Jest tests can be frustrating, but with a systematic approach, it can be resolved. By understanding the potential causes, such as configuration file issues, module loading order, and circular dependencies, and by applying the appropriate solutions, you can ensure that your tests run smoothly and reliably.

Remember, while workarounds can provide temporary relief, it's essential to address the root cause to prevent future issues. By following the steps outlined in this guide, you can effectively troubleshoot and resolve this problem in your Open edX frontend projects. Happy coding, and may your tests always pass!