Testing Command-Line Arguments with Jest

This challenge focuses on how to effectively test functions that process command-line arguments in a Node.js environment using Jest. Being able to mock and manipulate arguments is crucial for ensuring your CLI applications behave as expected under various input conditions.

Problem Description

You are tasked with writing Jest tests for a hypothetical Node.js command-line interface (CLI) application. Specifically, you need to test a function, processArgs, which takes command-line arguments as input and returns a structured object representing the parsed arguments. Your tests should cover different scenarios, including valid arguments, missing arguments, and invalid argument types.

Key Requirements:

1. Mock process.argv: You will need to mock the global process.argv array in your Jest tests to simulate different command-line inputs.
2. Test processArgs function: Implement a processArgs function that parses an array of strings (representing command-line arguments) and returns a JavaScript object.
3. Test Cases: Write comprehensive Jest test cases for processArgs that cover:
   • Parsing of basic key-value arguments (e.g., --name John).
   • Handling of boolean flags (e.g., --verbose).
   • Parsing of arguments with values containing spaces (e.g., --message "Hello World").
   • Scenarios with missing required arguments.
   • Scenarios with invalid argument formats.
4. Return Structure: The processArgs function should return an object where keys are the argument names and values are the parsed argument values. Boolean flags should be represented as true if present, and false otherwise.

Expected Behavior:

• The processArgs function should correctly parse arguments provided in the format --key value or --flag.
• It should handle arguments with spaces in their values if they are properly quoted.
• It should indicate when required arguments are missing or when arguments are malformed.

Examples

Example 1: Basic Argument Parsing

Input: ['node', 'your_script.js', '--name', 'Alice', '--age', '30']
processArgs would receive: ['--name', 'Alice', '--age', '30'] (after removing node and script path)
Output: { name: 'Alice', age: '30' }
Explanation: The function correctly parses the '--name' and '--age' arguments and their corresponding values.

Example 2: Boolean Flag and Quoted Value

Input: ['node', 'your_script.js', '--verbose', '--message', 'This is a test message']
processArgs would receive: ['--verbose', '--message', 'This is a test message']
Output: { verbose: true, message: 'This is a test message' }
Explanation: The '--verbose' flag is treated as a boolean true. The '--message' argument with spaces is parsed correctly because it's treated as a single value.

Example 3: Missing Required Argument

Input: ['node', 'your_script.js', '--name', 'Bob']
processArgs would receive: ['--name', 'Bob']
(Assume 'age' is a required argument)
Output: { name: 'Bob', error: 'Missing required argument: age' }
Explanation: The function detects that the required 'age' argument is missing and returns an error message.

Example 4: Invalid Argument Format

Input: ['node', 'your_script.js', '--name', 'Charlie', 'extra_arg']
processArgs would receive: ['--name', 'Charlie', 'extra_arg']
Output: { name: 'Charlie', error: 'Invalid argument format: extra_arg' }
Explanation: The unexpected 'extra_arg' is identified as an invalid argument format.

Constraints

• Arguments will be provided as an array of strings.
• The processArgs function will receive the array of arguments, excluding the first two elements (which typically represent the Node.js executable path and the script path).
• The processArgs function should aim to parse arguments efficiently, but extreme performance optimizations are not the primary focus for this challenge.
• Assume arguments follow the pattern --key value or --flag.

Notes

• You'll need to create a Jest test file (e.g., processArgs.test.ts).
• Inside your test file, you can use jest.spyOn or jest.mock to mock process.argv.
• Remember that process.argv in a real Node.js environment will always include the Node.js executable path and the script path as the first two elements. Your processArgs function should likely operate on process.argv.slice(2).
• Consider how you'll define which arguments are "required" and how your function will signal errors. For this challenge, returning an error property in the output object is a simple way to represent this.