What are some common code smells that indicate poor testability and how do you refactor them?

If we consider each module like a variable with different possible options and then switch cases accordingly, we can generate scenarios quickly, and from there we can move to more complex scenarios. Doing so at least gives a list of combinations to check instead of complicating the whole process.

Lengthy methods often signal low testability, making it challenging to isolate and test specific logic units. Refactoring long methods into smaller, task-focused functions facilitates the creation of more efficient unit tests.

Common code smells indicating poor testability include large classes/methods, tight coupling, lack of abstraction, complex conditional logic, inadequate error handling, and poorly named variables/functions. Refactor by breaking down large units, reducing dependencies, using abstraction layers, simplifying logic, improving error handling, and using meaningful names, adhering to SOLID principles and design patterns for better testability.

Common code smells indicating poor testability include long methods, complex conditional logic, and tight coupling. Refactor by breaking down methods into smaller, cohesive units, simplifying conditional logic, and decoupling dependencies through dependency injection or abstraction. Aim for single responsibility principle and clear separation of concerns for better testability.

?? Inappropriate Intimacy: - Classes/modules know too much about each other - Tight coupling, reduced modularity - Difficult mocking/stubbing ??? Refactoring: - Encapsulate field: private fields, public accessors/mutators - Move method/field: to appropriate class/module

When a class exhibits excessive intimacy with another, it complicates the creation of independent tests. Reduce dependency between classes by applying principles such as inversion of control or dependency injection, thereby improving testability.

Inappropriate intimacy occurs when classes/modules have excessive knowledge or access to each other's internal details, leading to tight coupling and reduced testability. Refactor by using encapsulation (private fields with public accessors/mutators), moving methods/fields to appropriate classes/modules, and applying SOLID principles for better modularity and testability.

Inappropriate intimacy in code refers to a situation where classes or functions know too much about each other's internal details, leading to tightly coupled code. This violates the principle of encapsulation and makes the codebase more difficult to maintain, as changes in one part can unexpectedly affect others. It often results in brittle code that’s hard to extend or refactor without introducing bugs. To reduce inappropriate intimacy, aim for well-defined interfaces and clear boundaries between classes or modules. Use principles like Dependency Injection, and strive for loose coupling by interacting through abstractions rather than concrete implementations.

"Feature envy" occurs when a class overly relies on another's attributes, leading to unwanted coupling. Abstract the logic related to features to make classes more independent and, consequently, more testable.

?? Feature Envy: - Method/class uses more data/functionality from another class/module - Indicates poor cohesion - Hard to test, lacks focus on responsibility/logic ??? Refactoring: - Move method/field: to class/module it's envious of - Extract class: encapsulate data/functionality in a new class/module

Feature envy occurs when a method or class relies more on data/functionality from another class/module than its own, leading to poor cohesion and difficult testing. Refactor by moving methods/fields to the appropriate class/module using the move method/field technique or extracting a new class/module using the extract class technique. This improves cohesion, focuses on responsibilities, and enhances testability.

?? Primitive Obsession: - Use primitive types for complex concepts - Lack validation, formatting, behavior - Code/logic duplication ??? Refactoring: - Introduce parameter object: class/module for related parameters - Replace data value with object: class/module for complex concepts represented by primitive types

Classes excessively manipulating primitive types can be challenging to test. Abstract logic related to primitive types into specific methods or helper classes to enhance testability and code readability.

Primitive obsession occurs when primitive types represent complex concepts, making testing difficult due to lack of validation, formatting, and behavior. Refactor using techniques like introduce parameter object (group related parameters in a class/module) or replace data value with object (use a class/module for complex concepts). This reduces duplication, improves validation, and enhances testability and maintainability.

Modifying multiple classes simultaneously during changes indicates low testability. Apply principles like the Open/Closed Principle to avoid the need for widespread changes, making test writing and maintenance more straightforward.

?? Shotgun Surgery: - Single change requires many small changes in different classes/modules - Indicates high coupling, low cohesion - Hard to test, poorly structured system ??? Refactoring: - Move method/field: to single class/module affected by change - Extract class: encapsulate affected functionality in new class/module

Shotgun surgery occurs when a single change requires multiple small changes in different parts of the system, indicating high coupling and low cohesion. Refactor by using the move method/field technique to consolidate changes in a single class/module or by using the extract class technique to encapsulate affected functionality in a new class/module. This improves modularity, reduces coupling, and makes testing easier and more efficient.

Classes that don't do enough may indicate low testability, as they don't provide specific functionalities to test. Refactor lazy classes by consolidating related functionalities, ensuring each class has a clear and testable responsibility.

?? Lazy Class: - Class/module doesn't justify its existence - Adds unnecessary complexity - Hard to test, lacks clear tests ??? Refactoring: - Inline class: merge with another class/module - Collapse hierarchy: remove subclass/superclass with no added value

Lazy class refers to a class or module that doesn't justify its existence due to minimal functionality, adding unnecessary complexity to the system and complicating testing. Refactor by using the inline class technique to merge it with another class/module or collapse hierarchy by eliminating redundant subclasses/superclasses. These techniques streamline the system, reduce complexity, and improve testability by focusing on essential functionality.