Test Driven Development by Robert C. Martin
What Is Test Driven Development (TDD)?
Test Driven Development (TDD) is a core practice of agile software development where tests are written before the actual code. Coined and popularized by experts like Robert C. Martin (Uncle Bob), TDD helps ensure code correctness, improves design, and builds confidence during refactoring.
Robert C. Martin’s TDD Cycle: Red-Green-Refactor
1. Red — Write a Failing Test
Start by writing a unit test for the feature or behavior you want to implement. This test should fail initially because the functionality doesn’t exist yet.
2. Green — Write the Minimum Code to Pass
Write just enough code to make the failing test pass. Don’t worry about design or duplication yet—just get it to work.
3. Refactor — Clean the Code
Once the test passes, improve the code structure while keeping the tests green. Refactor without changing behavior.
Benefits of TDD
- Better Code Quality: Forces you to think before coding.
- Fewer Bugs: Catch issues early through automated tests.
- Safe Refactoring: Tests act as a safety net when changing code.
- Improved Design: Encourages loosely coupled, modular code.
Real-World Example (C#)
✅ Step 1: Write the Failing Test
// CalculatorTests.cs
[TestMethod]
public void Add_ReturnsSumOfTwoNumbers()
{
var calculator = new Calculator();
var result = calculator.Add(2, 3);
Assert.AreEqual(5, result);
}
✅ Step 2: Make It Pass
// Calculator.cs
public class Calculator
{
public int Add(int a, int b)
{
return a + b;
}
}
✅ Step 3: Refactor (If Needed)
In this case, the code is already clean, but in more complex scenarios, you'd now improve the structure, naming, or performance.
Common TDD Mistakes to Avoid
- Writing too many tests before implementation
- Skipping the refactoring step
- Writing overly specific or fragile tests
- Not running tests frequently
Uncle Bob’s Advice on TDD
"The only way to go fast, is to go well." — Robert C. Martin
Uncle Bob emphasizes that TDD isn’t just a testing technique—it's a design and development discipline that helps teams build better software faster and with confidence.
Conclusion
Test Driven Development as taught by Robert C. Martin brings discipline and clarity to modern software development. By following the Red-Green-Refactor cycle, developers can create well-designed, reliable, and maintainable applications.
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