swift-tdd

Swift TDD Command

This command invokes the swift-tdd-guide agent to enforce test-driven development methodology for iOS projects.

What This Command Does

1. Define Protocols - Establish contracts and interfaces first
2. Write Tests First - Create failing tests using Swift Testing (RED)
3. Implement Minimal Code - Write just enough to pass (GREEN)
4. Refactor - Improve code while keeping tests green (REFACTOR)
5. Verify Coverage - Ensure 80%+ test coverage

When to Use

Use /swift-tdd when:

• Implementing new iOS features
• Adding new ViewModels, UseCases, or Repositories
• Fixing bugs (write test that reproduces bug first)
• Refactoring existing Swift code
• Building critical business logic

How It Works

The swift-tdd-guide agent will:

1. Define protocols for dependencies and contracts
2. Write tests that will FAIL (because code doesn't exist yet)
3. Run tests and verify they fail for the right reason
4. Write minimal implementation to make tests pass
5. Run tests and verify they pass
6. Refactor code while keeping tests green
7. Check coverage and add more tests if below 80%

TDD Cycle

RED → GREEN → REFACTOR → REPEAT

RED:      Write a failing test using #expect
GREEN:    Write minimal code to pass
REFACTOR: Improve code, keep tests passing
REPEAT:   Next feature/scenario

Example Usage

User: /swift-tdd I need a use case to calculate market liquidity score

Agent (swift-tdd-guide):
# TDD Session: Market Liquidity Score Calculator

## Step 1: Define Protocol (SCAFFOLD)

```swift
// Domain/UseCases/LiquidityCalculator.swift
import Foundation

struct MarketData: Sendable {
    let totalVolume: Double
    let bidAskSpread: Double
    let activeTraders: Int
    let lastTradeTime: Date
}

protocol LiquidityCalculating: Sendable {
    func calculateScore(for market: MarketData) -> Double
}

// Placeholder implementation
struct LiquidityCalculator: LiquidityCalculating {
    func calculateScore(for market: MarketData) -> Double {
        fatalError("Not implemented")
    }
}

Step 2: Write Failing Test (RED)

// Tests/Domain/LiquidityCalculatorTests.swift
import Testing
@testable import MyApp