🧪 TDD — More Than Just Writing Tests First

There’s something beautiful about writing code that you’re confident in — not because it “worked on your machine,” but because it was born through a cycle of thoughtful feedback.
That’s what TDD — or Test-Driven Development — brings to the table.

But let’s be honest.
Most developers know TDD “in theory,” yet very few practice it consistently.
Why?
Because it feels slower. Because it requires discipline. Because writing tests first feels unnatural.

But I’ll argue this: Not doing TDD might feel faster, but it rarely is.
What it buys you in speed now, it robs you in refactors, regressions, and late-night production fixes later.

Let’s walk through an example and see what it really feels like in practice.

🧱 The Core Loop of TDD

TDD is a cycle. Always.

1. Write a failing test (Red)
2. Write the minimum code to make it pass (Green)
3. Refactor with confidence (Refactor)
4. Repeat 🔁

🧠 Problem Statement

Let’s say we’re writing a simple utility class in Java:

Implement a StringCalculator with a method add(String numbers).
The method should take a comma-separated string of numbers and return their sum.

🧪 Step 1: Write the First Test (Red)

@Test
void shouldReturnZeroWhenInputIsEmpty() {
    StringCalculator calc = new StringCalculator();
    int result = calc.add("");
    assertEquals(0, result);
}

This test doesn’t compile yet. That’s fine. That’s expected.

🧱 Step 2: Write Just Enough Code (Green)

public class StringCalculator {
    public int add(String numbers) {
        return 0;
    }
}

✅ Test passes.
Yeah, it’s a dumb implementation. But it’s fine for now.
Remember: “You’re not building the full feature. You’re earning the right to write more code.”

🧪 Step 3: Next Test Case

@Test
void shouldReturnNumberWhenSingleNumberIsProvided() {
    StringCalculator calc = new StringCalculator();
    int result = calc.add("5");
    assertEquals(5, result);
}

🔴 This fails.

✅ Now, Update Implementation

public int add(String numbers) {
    if (numbers.isEmpty()) return 0;
    return Integer.parseInt(numbers);
}

🟢 Green again.

🧪 Step 4: Handle Multiple Numbers

@Test
void shouldReturnSumWhenMultipleNumbersAreProvided() {
    StringCalculator calc = new StringCalculator();
    int result = calc.add("1,2,3");
    assertEquals(6, result);
}

🔴 Red. Good.

✅ Refactor to Handle It

public int add(String numbers) {
    if (numbers.isEmpty()) return 0;
    String[] parts = numbers.split(",");
    int sum = 0;
    for (String part : parts) {
        sum += Integer.parseInt(part);
    }
    return sum;
}

🟢 Green.

You see the pattern?
You’re always working in short, quick cycles.
You’re never guessing. Never hacking.

You write code only when a test demands it.

💡 Why This Matters (a lot)

TDD isn’t just about tests. It’s a way of thinking. Your design improves because:

• You think in use cases, not implementation
• You handle edge cases early
• You build just enough — not more

It also pays dividends in long-term maintenance. Refactors are easier. Bugs are rare. The team moves with trust.

☕️ Real-Life Application

You might not use TDD for everything. Sometimes, you’re spiking or exploring.

But for anything with business logic, anything with edge cases — it’s a game-changer.

So start small. Write the failing test first. See how it shapes the code you write.

Conclusion

You might hate TDD at first. It feels like training wheels.
But the truth is — most of us crash more than we admit.

Maybe it's time we put them on.