Refactoring in TDD: Rename Method

This snippet demonstrates the 'Rename Method' refactoring technique in TDD. This refactoring involves changing the name of a method to better reflect its purpose. This is crucial for code clarity and maintainability. A poorly named method can be confusing and make it difficult for others (and your future self) to understand what the method does. The TDD approach ensures that renaming the method doesn't break any existing functionality, as all tests should still pass after the rename.

Original Code (Before Refactoring)

Here, the method `doCalc` is not very descriptive. It doesn't clearly indicate that it's performing an addition. The tests verify that the method returns the correct sum.

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class Calculator {

    public int doCalc(int a, int b) {
        return a + b;
    }
}

class CalculatorTest {
    @Test
    void testDoCalc() {
        Calculator calculator = new Calculator();
        assertEquals(5, calculator.doCalc(2, 3));
    }
}

Refactored Code (After Rename Method)

The method `doCalc` has been renamed to `add`, which more accurately reflects its functionality. The test `testDoCalc` has also been renamed to `testAdd` to match the method name. The tests still pass, ensuring the functionality remains the same.

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class Calculator {

    public int add(int a, int b) {
        return a + b;
    }
}

class CalculatorTest {
    @Test
    void testAdd() {
        Calculator calculator = new Calculator();
        assertEquals(5, calculator.add(2, 3));
    }
}

Concepts Behind the Snippet

• TDD: Emphasizes writing tests before implementing code.
• Refactoring: Improves code structure without changing external behavior.
• Rename Method: A refactoring technique for improving method names to accurately reflect their purpose.
• Code Clarity: Making the code easier to understand.

Real-Life Use Case

Consider a method named `processData` in a data processing application. If the method specifically performs data validation, renaming it to `validateData` would make its purpose much clearer to other developers.

Best Practices

• Choose descriptive names: Method names should clearly indicate what the method does.
• Follow naming conventions: Adhere to the project's naming conventions (e.g., using verbs for method names).
• Update all references: Ensure that all references to the method are updated after renaming it.

When to Use Them

Use 'Rename Method' when:

• The method name is not descriptive enough.
• The method name is misleading or inaccurate.
• The method name does not follow the project's naming conventions.

Pros

• Improved code readability and understanding.
• Reduced confusion and errors.

Cons

• Can be time-consuming if the method is used in many places.
• Requires careful attention to detail to avoid breaking existing functionality.

Interview Tip

Be prepared to explain why choosing descriptive names is crucial for maintainable code, and to discuss how TDD helps guarantee you don't break existing functionality when refactoring by renaming methods.