Add ‘mission’ CLI Command, Tests, And Documentation

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As we continue to develop our CLI application, it's essential to ensure that our codebase accurately reflects our mission-driven design. In this article, we'll delve into the process of implementing the mission CLI command, writing comprehensive tests, and updating our documentation to align with our mission.

Refactoring the CLI Stub: Implementing the Mission Command

The current CLI stub in src/lib/main.js only echoes arguments, failing to implement the documented mission command. To address this, we'll refactor the main(args) function into an async router. If the first argument is mission, we'll read the contents of MISSION.md and print them to stdout.

Refactoring main(args) into an Async Router

// src/lib/main.js
import { fileURLToPath } from 'url';
import { readFile } from 'fs/promises';

const missionFile = fileURLToPath(new URL('MISSION.md', import.meta.url));

async function main(args) {
  if (args[0] === 'mission') {
    try {
      const missionContent = await readFile(missionFile, 'utf8');
      console.log(missionContent);
      process.exit(0);
    } catch (error) {
      console.error(error);
      process.exit(1);
    }
  } else {
    // Preserve existing behavior for other commands
    console.log('Echoing arguments:', args.join(' '));
  }
}

export default main;

In this refactored code, we use fs/promises to read the contents of MISSION.md and fileURLToPath to locate the file. If the first argument is mission, we print the contents to stdout and exit with code 0. For other commands, we preserve the existing behavior by echoing the arguments.

Writing Comprehensive Tests: Verifying the Mission Command

To ensure that our implementation is correct, we'll write comprehensive tests for the mission command. We'll add a new describe block in tests/unit/main.test.js and write a test that stubs or spies on fs.promises.readFile to return a known string.

Writing Tests for the Mission Command

// tests/unit/main.test.js
import { describe, it, expect } from 'vitest';
import { main } from '../lib/main';
import { spy } from 'sinon';
import { readFile } from 'fs/promises';

describe('mission command', () => {
  it('prints the mission statement', async () => {
    const readFileSpy = spy(readFile);
    readFileSpy.resolves('# Mission Test');

    const stdout = await main(['mission']);
    expect(stdout).toContain('# Mission Test');
    expect(readFileSpy.calledOnce).toBe(true);
  });
});

In this test, we use vitest to write a test that invokes await main(['mission']) and asserts that stdout contains the stubbed content and the process does not throw. We also ensure that the test import uses the same mocks and restores them after.

Updating Documentation: Adding the Mission Command

To complete our implementation, we'll update our documentation to include the mission command. We'll add a Usage in README.md and link to MISSION.md in the README summary.

Updating README.md

# Usage

## Print the mission statement

```bash
npm run start mission

Mission Statement

Read our mission statement in MISSION.md.


In this updated documentation, we add a **Usage** section for the `mission` command and link to `MISSION.md` in the README summary.

**Conclusion**
----------

In this article, we've implemented the `mission` CLI command, written comprehensive tests, and updated our documentation to align with our mission-driven design. By following these steps, we've ensured that our codebase accurately reflects our mission and provides a seamless user experience.

**Running Tests and Verifying the Mission Text**
----------------------------------------------

To confirm that our tests pass and the mission text prints as expected, we'll run `npm test` and `npm run start mission`.

```bash
npm test
npm run start mission

In our previous article, we implemented the mission CLI command, wrote comprehensive tests, and updated our documentation to align with our mission-driven design. In this Q&A article, we'll address some common questions and provide additional insights into the implementation process.

Q: Why is it essential to implement the mission CLI command?

A: Implementing the mission CLI command is crucial because it reflects our mission-driven design. By including the mission command, we ensure that our codebase accurately represents our values and goals. This not only enhances our user experience but also reinforces our brand identity.

Q: How do I refactor the CLI stub to implement the mission command?

A: To refactor the CLI stub, you'll need to modify the main(args) function to check if the first argument is mission. If it is, you'll read the contents of MISSION.md and print them to stdout. You can use fs/promises to read the file and fileURLToPath to locate the file.

Q: What are the key differences between the refactored code and the original code?

A: The key differences between the refactored code and the original code are:

  • The main(args) function is now an async router.
  • The code checks if the first argument is mission and reads the contents of MISSION.md if it is.
  • The code preserves the existing behavior for other commands.

Q: How do I write comprehensive tests for the mission command?

A: To write comprehensive tests for the mission command, you'll need to add a new describe block in tests/unit/main.test.js. You'll then write a test that stubs or spies on fs.promises.readFile to return a known string. This will ensure that the mission command prints the correct content and exits with code 0.

Q: What are the benefits of using fs/promises and fileURLToPath in the refactored code?

A: Using fs/promises and fileURLToPath in the refactored code provides several benefits, including:

  • Improved performance: fs/promises is a promise-based API that allows for asynchronous file I/O.
  • Enhanced security: fileURLToPath helps prevent directory traversal attacks by ensuring that the file path is correctly resolved.

Q: How do I update the documentation to include the mission command?

A: To update the documentation, you'll need to add a Usage section in README.md and link to MISSION.md in the README summary. This will ensure that users can easily access the mission statement and understand how to use the mission command.

Q: What are the key takeaways from implementing the mission CLI command?

A: The key takeaways from implementing the mission CLI command are:

  • Implementing the mission command reflects our mission-driven design.
  • Refactoring the CLI stub requires checking if the first argument is mission and reading the contents of MISSION.md if it is.
  • Writing comprehensive tests involves stubbing or spying on fs.promises.readFile to return known string.
  • Updating the documentation requires adding a Usage section and linking to MISSION.md.

By following these steps and addressing these questions, you'll be able to implement the mission CLI command and enhance your user experience.