Achieve 100% Branch Coverage in Jest for Conditional Logic

Testing is crucial for ensuring code quality and reliability. While line coverage indicates that all lines of code have been executed, branch coverage goes a step further by ensuring that all possible execution paths (branches) within conditional statements are tested. This challenge focuses on achieving 100% branch coverage in Jest for a given TypeScript function.

Problem Description

You are provided with a TypeScript function that contains conditional logic (if statements, ternary operators, etc.). Your task is to write Jest tests that guarantee every possible branch of the conditional logic within this function is executed at least once. This means for every if statement, you must test both the condition being true and the condition being false. Similarly, for other conditional structures, all outcomes must be covered.

What needs to be achieved: Write a set of Jest tests for the provided processUserData function that results in 100% branch coverage when run with Jest's coverage reporting.

Key requirements:

• Tests must be written in TypeScript.
• Tests must use the Jest testing framework.
• The tests should cover all branches of the conditional logic within the processUserData function.
• The tests should pass when run with jest --coverage.

Expected behavior: Upon running jest --coverage, the generated coverage report should show 100% branch coverage for the processUserData function.

Important edge cases to consider:

• Input values that trigger different conditional paths.
• Boundary conditions for numeric or string inputs.
• Null or undefined inputs if applicable (though the provided function has defined types).

Examples

Let's assume the following TypeScript function:

// src/userUtils.ts
export function processUserData(user: { name: string; age: number; isActive: boolean }): string {
  let message = `Hello, ${user.name}!`;

  if (user.age < 18) {
    message += " You are a minor.";
  } else if (user.age >= 18 && user.age < 65) {
    message += " You are an adult.";
  } else {
    message += " You are a senior.";
  }

  if (user.isActive) {
    message += " Your account is active.";
  } else {
    message += " Your account is inactive.";
  }

  return message;
}

Example 1: Testing a young, active user

Input:

const user1 = { name: "Alice", age: 16, isActive: true };

Expected Output (when processUserData(user1) is called):

"Hello, Alice! You are a minor. Your account is active."

Example 2: Testing an adult, inactive user

Input:

const user2 = { name: "Bob", age: 30, isActive: false };

Expected Output (when processUserData(user2) is called):

"Hello, Bob! You are an adult. Your account is inactive."

Example 3: Testing a senior, active user

Input:

const user3 = { name: "Charlie", age: 70, isActive: true };

Expected Output (when processUserData(user3) is called):

"Hello, Charlie! You are a senior. Your account is active."

Example 4: Testing a senior, inactive user

Input:

const user4 = { name: "David", age: 70, isActive: false };

Expected Output (when processUserData(user4) is called):

"Hello, David! You are a senior. Your account is inactive."

Constraints

• The provided processUserData function in src/userUtils.ts must be tested.
• Your test file should be named userUtils.test.ts and placed in a __tests__ directory or alongside the source file, as per Jest's convention.
• You must achieve exactly 100% branch coverage. No more, no less.

Notes

• Remember that branch coverage requires testing all possible outcomes of a conditional statement. For an if/else if/else structure, you need to ensure each condition path is hit. For an if/else, you need to test both the if block and the else block.
• Consider the different age ranges (under 18, 18-64, 65+) and the isActive status.
• You will need to set up Jest and TypeScript in your project if you haven't already. A typical Jest setup for TypeScript involves installing jest, ts-jest, and @types/jest. You'll also need a jest.config.js file.
• To check your coverage, run jest --coverage. The output will include a coverage/lcov-report/index.html file that provides a detailed breakdown. Your goal is to see "100%" for branch coverage for userUtils.ts.
• Think about the specific input values that will push execution down each distinct branch.