refactor-extract-and-isolate

Extract method refactoring isolates logic from a larger function into focused, named units. Identify boundaries within the function, create a new method with a clear name, move the code, update references, and add tests to verify behavior remains unchanged.

Extract a class when responsibilities are mixed or a class exceeds 300 lines. Identify distinct concerns, move related methods and state to a new class, and update references. This improves testability and maintainability.

Deep nesting and repeated logic signal extraction opportunities. Functions exceeding 20 lines, classes over 300 lines, or duplicated code blocks indicate mixed concerns. Refactoring isolates these patterns into focused units for clarity.

Yes. Refactoring identifies extraction boundaries, moves code into new units, and updates all references while maintaining original behavior. Adding tests before and after extraction verifies that functionality remains intact.

Extracting a method moves logic into a named function within the same scope. Extracting an interface creates an abstraction for multiple implementations, enabling dependency inversion and easier testing across different classes.

Yes. After extraction, add tests for the new isolated unit to verify correct behavior independently. Update existing tests to reflect refactored references, ensuring the original behavior and new boundaries are validated.