What Are Some Common Code Smells That Indicate Poor Testability, And How Do You Refactor Them?

Recently, there has been a notable shift towards automation testing in the software development industry. This approach offers numerous benefits, such as faster and more reliable testing, boosted test coverage, and diminished manual efforts. Nonetheless, the success of automation testing heavily relies on the quality of the code being tested. Inadequately written code has the potential to yield code smells, which serve as indicators of potential issues within the codebase.

These code smells affect the code’s maintainability and readability and hinder the application’s testability. Code smells are tangible and perceptible evidence that something is amiss with the app’s underlying code. It can degrade the app’s performance and increase the technical debt if left unaddressed. Further, this makes it difficult for the software development teams to furnish value over time and deliver the software faster to the market.

What is Code Smell?

A code smell is an issue in source code that is not a bug or is strictly technically wrong. The code will still compile and function as expected. However, it highlights a deviation from established design principles that could result in future complications. Simply put, code smell is a sign that the source code is cluttered and does not meet the best practice standards.

Code smell highlights the presence of tie-ups in the codebase that require immediate attention. If not, they can diminish the code quality, maintainability, and readability. Besides, smelly code can become rotten code if not taken care of in the earlier stages. One of the reasons for code rot is technical debt. Therefore, occasionally checking and rectifying them is advisable to prevent technical debt and code rot.

Code Smells and their Solutions

Code smells, like refactorings and design patterns, have been cataloged for decades. Specific terminology is used to identify the most prevalent ones and is classified into distinct categories based on their characteristics. Tracking code smells provides you a fighting chance against issues in your code. You can witness concerning trends and act accordingly against them before they become a severe issue.

Here are a few common code smells that indicate poor testability and effective ways to refactor them:

Duplicate Code and Abstraction

Duplicated code is a code smell that indicates poor testability. This occurs when identical code is present in multiple sections, typically because the code is copied and pasted into different program parts. Although it may look innocuous, it becomes problematic as the software developer has to make numerous tweaks during feature updates.

Duplicated code diminishes the code maintainability and results in inconsistent application. This happens because the change was not applied uniformly. This significantly elongates the cycle time and is also a potential business risk.

To refactor duplicate code, developers can employ the abstraction principle. Abstraction involves identifying common patterns or functionalities in the duplicated code and creating reusable abstractions, such as functions, classes, or libraries, to encapsulate and handle those patterns. Leverage the power of loops or functions to make code appear once in a program. Utilize refactoring techniques, such as the pull-up method, extract method, and substitute algorithm.

Excessive Complexity

When code becomes excessively complex, it becomes easier to comprehend and maintain, posing challenges in writing adequate tests. To effectively resolve this matter, developers can employ the principle of separation of concerns to dissect the code into smaller, more manageable components. This approach authorizes for improved organization and enhances the overall maintainability of the codebase.

Breaking down complex functionalities into smaller functions or classes makes it easier to test each component individually and pinpoint any potential issues. Besides, refactoring techniques such as extracting methods or entangling design patterns can help simplify the code and improve its testability.

Long Test Methods and Readability


The long test methods and poor readability occur when the test method has too long and complex lines of code. It becomes difficult to understand the purpose and functionality of each test. There is no specific number of code lines that are considered to be long. Some consider it twenty-five, while others think fifty is excessively long.

The long test method code smell transgresses the single responsibility principle. This approach poses challenges when incorporating new features or updating existing ones. It becomes harder to understand, test, and debug the code. This increases the cyclomatic complexity and leads to unexpected bugs.

To refactor long test methods and improve readability, developers can break down the tests into smaller, more focused units. This can be achieved by extracting setup and teardown code into separate methods, using descriptive method and variable names, and organizing the tests logically and cohesively. Also, remove parameters and local variables before extracting a method.

Tight Coupling and Dependency Injection

Tight coupling refers to a design approach where classes and modules depend heavily on one another, making it difficult to isolate and test individual components. This can lead to the creation of intricate and fragile test cases that pose challenges in maintenance and modification. On the other hand, dependency injection promotes loose coupling by authorizing dependencies to be injected into a class from the outside.

By refactoring code to use dependency injection, developers can easily swap out dependencies with mock objects during testing. This enables more focused and independent unit tests. Further, this improves the testability of the code and enhances its overall flexibility, scalability, and maintainability.

Dead Code

The code becomes dead when the developers neglect to perform code cleanup, lack awareness of dead code, or permit remnants of deprecated code to linger. The code is currently unnecessary. However, it remains within the application. It can be a parameter, variable, field, class, or method. Dead code makes the application hard to understand, more security vulnerabilities, and increases bugs and errors.

The amount of dead code in the application indicates:

  • The way projects were managed
  • The team’s level of commitment towards addressing technical debt
  • The level of communication between the parties involved

Developers can replace the functionality of the application by removing the dead code. Utilize static analysis tools or integrated development environments (IDEs) such as Visual Studio to identify and eliminate unused code. These tools can effectively suggest and prompt the removal of any code not being utilized in the project. Developers can also use refactor code to swap out redundancies and maintain structure.

Complex Conditional Statements and Simplification


Complex conditional statements can often be a code smell that indicates poor testability. Writing comprehensive tests covering all possible scenarios becomes challenging when conditional statements become convoluted and filled with multiple nested conditions. Furthermore, the utilization of intricate conditional statements has the potential to result in code that is challenging to comprehend, decipher, and uphold.

To address this issue effectively, it is crucial to streamline and simplify these statements by breaking them into smaller, more manageable components. This can be attained by extracting conditional blocks into separate functions or utilizing switch statements where appropriate. By simplifying complex conditionals, the code becomes more testable, readable, maintainable, and less prone to errors.

Lazy Class

Lazy class code smell occurs when a class exists yet does not contribute to the behavior or function of the software. This leads to an elevation in the complexity of the code and results in a cluttered code base. As a result, the heightened cognitive load imposed on developers leads to increased expenditure of both time and financial resources.

If left unaddressed for a prolonged time, lazy class can result in future risk. Expanding the functionality of the lazy class may result in an overly complex or inadequately structured class.

To address this issue, implement constant code reviews to pinpoint and address lazy classes. Evaluate the legitimate purpose of the ‘lazy class’ within the codebase. It can be eliminated using the remove class technique if not necessary. Utilize the “inline class technique” to identify and consolidate a lazy class with another class that utilizes its functionality.

Hard-Coded Values and Variables

Hard-coded values refer to specific numbers, strings, or other literal values directly embedded into the code. This can make modifying or updating these values difficult without manually searching and replacing them throughout the codebase. Similarly, hard-coded variables can make writing comprehensive test cases that cover different scenarios and input variations challenging.

To refactor this code smell, extracting these hard-coded values and variables into reusable constants or configuration files is recommended. Doing so makes the code more flexible, maintainable, and easier to test, as any changes or updates can be made in a centralized location rather than scattered throughout the code.

Primitive Obsession

Primitive obsession is another type of code smell that developers can not identify intuitively. This happens when a primitive value assumes control over the logic within a class and is used to represent intricate concepts or behaviors. In simple words, primitive obsession occurs when a code depends too much on primitive values.

Relying solely on primitives for all tasks is deemed a flawed practice in professional settings. This leads to poor validation, readability, and abstraction.

Developers can address this issue by substituting the data value with the corresponding object if the primitive fields are logically connected. Implementing a parameter object is recommended to represent the data and enhance the overall code structure.

Lack of Modularity

When test code is tightly coupled with production code, isolating individual components for testing becomes challenging. To refactor this, developers can leverage cloud testing tools that furnish virtual test environments.

LambdaTest is a robust cloud testing platform designed to streamline and enhance the automated testing process for developers and testers. One key strength lies in its ability to automate complex and uncertain scenarios, providing a reliable solution for addressing varied testing requirements.

The platform AI-powered test execution and orchestration capabilities set it apart in automation testing. With LambdaTest, users can access an extensive grid of over 3000 real browsers and operating system combinations. This diverse testing environment provides comprehensive coverage, ensuring that applications are thoroughly tested across various configurations.

Using these tools, developers can create isolated test environments, guaranteeing that each component is tested in isolation without any dependencies on other modules. Cloud testing tools can also facilitate parallel test execution capabilities, authorizing developers to run multiple smaller tests simultaneously and reducing the overall complexity.


A code smell is a common issue developers face, implying the potential problem within a codebase. It is essential to address code smell early, or it can lower the code quality and hinder the entire development process.

Through proper use of design patterns, clean coding practices, and continuous refactoring, developers can improve their code’s testability and ultimately save time and resources in the long run. By prioritizing testability in the development process, developers can deliver high-quality, bug-free software to clients and maintain a competitive edge in the market.