green

TDD Green Phase

You are now in the Green Phase of TDD. Follow these instructions to make the failing test pass with MINIMAL code.

Your Mission

1. Implement the minimal code necessary to make the failing test pass
2. Use the simplest possible solution (hardcoded values are acceptable)
3. Avoid adding features for future tests
4. Verify all tests pass
5. NO optimization, NO refactoring yet

Context: $ARGUMENTS

Green Phase Rules

• Minimal code only: Just enough to pass the current test
• Baby steps: Make the smallest possible change
• No future features: Don't implement what future tests might need
• Simple is better: Hardcoded returns are perfectly fine
• Tests must pass: Verify all tests are green
• No refactoring yet: Save improvements for Refactor phase

Process

Step 1: Analyze the Failing Test

Understand what the test expects:

• What input does the test provide?
• What output does it expect?
• What is the simplest way to produce that output?

Step 2: Write Minimal Implementation

Implement only what's needed to make the current test pass:

// For first test "should return 0 for empty input":
export const calculate = (input: string): number => {
  return 0; // Minimal - just make the test pass
};

// For second test "should return number for single input":
export const calculate = (input: string): number => {
  if (input === "") return 0;
  return parseInt(input); // Still simple
};

// For third test "should add two numbers":
export const calculate = (input: string): number => {
  if (input === "") return 0;
  const numbers = input.split(",");
  if (numbers.length === 1) return parseInt(numbers[0]);
  return parseInt(numbers[0]) + parseInt(numbers[1]); // Only now add logic
};

Step 3: Run Tests

Run npm test and verify:

• Current test now passes ✅
• All previous tests still pass ✅

Step 4: Verify No Over-Implementation

Check yourself:

• ❓ Did I implement features for future tests? → Remove them
• ❓ Did I add logic not demanded by current test? → Remove it
• ❓ Did I optimize prematurely? → Simplify
• ❓ Did I refactor existing code? → Revert, save for Refactor phase