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Test-driven development (TDD)

tdd

Test-driven development (TDD) is a software development methodology that emphasizes writing automated tests before writing the code that will be tested. The goal of TDD is to catch bugs early and ensure that the code meets its requirements. In this blog post, we'll walk through an example of TDD to show how it works in practice.

Step 1: Write a test #

The first step in TDD is to write a test that describes the behavior you want your code to have. For example, let's say we're building a simple calculator that can add two numbers together. We'll start by writing a test that checks that the calculator can add two numbers together correctly.

def test_calculator_addition():
    calculator = Calculator()
    result = calculator.add(2, 3)
    assert result == 5

Step 2: Run the test and see it fail #

Next, we'll run the test and see that it fails because the Calculator class doesn't exist and the add method is not defined. This is expected, since we haven't written any code yet.

Step 3: Write the code #

Now that we have a failing test, we'll write the code to make the test pass. In this case, we'll create a Calculator class and an add method that adds two numbers together.

class Calculator:
    def add(self, x, y):
        return x + y

Step 4: Run the test again and see it pass #

After writing the code, we'll run the test again. This time, the test should pass because the code correctly adds two numbers together.

Step 5: Repeat #

We can continue to add more tests and more functionality to the calculator, following the same pattern of writing a test, seeing it fail, writing the code, and seeing the test pass.

Conclusion #

In this example, we've shown how TDD can be used to guide the development of a small piece of code. By writing tests first, we can be sure that our code is correct and that it meets the requirements we've set out. Additionally, because we've written tests, we can be confident that future changes to the code won't break existing functionality.

TDD is a powerful tool for software development, and by following these steps, you can use it to build high-quality code that is easy to maintain and extend.