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What is the key to writing effective unit tests?

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Unit testing is a fundamental practice in software development that involves verifying the functionality of individual components or units of code. Unit tests can help you catch bugs early, improve code quality, and facilitate refactoring and maintenance. But what is the key to writing effective unit tests that actually add value to your project and not just increase complexity and overhead? In this article, you will learn some essential principles and tips to follow when writing unit tests, as well as some common pitfalls to avoid.

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Paras Sidhu

Senior Engineer @ LinkedIn ????
Baubak Gandomi

Senior QE Architect
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Freelance Software Engineer @ Toptal | Solving Problems and Building Scalable Solutions

1 Define clear and specific test cases

The first step to writing effective unit tests is to define clear and specific test cases that cover the expected behavior and outcomes of your code. Test cases should be based on the requirements and specifications of your code, not on its implementation details. You should also consider different scenarios, edge cases, and inputs that might affect your code's performance and functionality. A good way to define test cases is to use the AAA pattern: Arrange, Act, and Assert. This means that you should set up the initial conditions and inputs for your test, execute the code or method under test, and verify the results or effects of your code.

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Paras Sidhu

Senior Engineer @ LinkedIn ????
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A very fundamental rule is to test the behavior and not the implementation. Many developers get biased and just try to test if their implementation work correctly. It may not be the correct indicator of if the class's behavior is as intended. While writing unit tests, think why would someone use the public APIs which are to be tested? What behavior would the consumer expect?

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2 Follow naming and organization conventions

The next step to writing effective unit tests is to follow naming and organization conventions that make your tests easy to read, understand, and maintain. You should use descriptive and consistent names for your test classes, methods, and variables that indicate what they are testing and what they expect. You should also organize your tests in a logical and hierarchical structure that reflects the structure of your code. For example, you can use folders, namespaces, or categories to group your tests by functionality, feature, or module. You should also use test frameworks and tools that support your naming and organization conventions and provide useful features such as annotations, assertions, and runners.

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3 Write isolated and independent tests

Another key to writing effective unit tests is to write isolated and independent tests that do not depend on each other or on external factors. Isolated and independent tests are easier to run, debug, and maintain, as they do not cause side effects or interfere with other tests. To achieve isolation and independence, you should avoid using shared or global state, such as static variables, singletons, or databases, in your tests. Instead, you should use mocks, stubs, or fakes to simulate or replace the dependencies or interactions of your code with other components or systems. You should also use setup and teardown methods to initialize and clean up the resources or state needed for each test.

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Baubak Gandomi

Senior QE Architect
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Unit tests are all about abstraction. By this, I mean that a unit test, ideally and for the most part, should only have two actors: * Test * The code you test It means that if the test fails, you need to only look at one source of error. Sometimes we tend include data in files for processing. Inb these cases you are actually introducing an additional actor that could be prone to errors. Ideall you should avoid system proprties, and static variable, as thy caus problems in general, and are brittle during parallelsim. However, if you have. to you need to have a propoer cleanup policy. If you have system variables, it is a good idea to have a dedicated handler, or even better, abstract them from the executor code.

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4 Write maintainable and reusable tests

One more key to writing effective unit tests is to write maintainable and reusable tests that can adapt to changes in your code and requirements without breaking or requiring extensive modifications. Maintainable and reusable tests are more reliable and valuable, as they can ensure the quality and functionality of your code over time. To write maintainable and reusable tests, you should follow the DRY principle: Don't Repeat Yourself. This means that you should avoid duplicating code or logic in your tests, and instead use helper methods, constants, or data sources to abstract and centralize common or complex operations or values. You should also follow the SOLID principles: Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion. These principles can help you design your code and tests in a modular, flexible, and extensible way.

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Baubak Gandomi

Senior QE Architect
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One way of writing reuseable tests, is for the tests scripts to avoid directly accessing the system under test. This means that you divide the test code into two parts. The test script itself which is purely functional, and the code that accesses the system, which can be reused in other tests. One intuition is that if your test has complexity you need to extract it into a helper. BDD coding would naturally have this, but also the page object pattern follows this principle.

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5 Write readable and expressive tests

The last key to writing effective unit tests is to write readable and expressive tests that convey the intent and meaning of your tests clearly and concisely. Readable and expressive tests are easier to comprehend, review, and communicate, as they can tell a story about your code and its behavior. To write readable and expressive tests, you should use meaningful and consistent names, formatting, and indentation for your tests. You should also use fluent and natural language for your assertions, such as BDD (Behavior-Driven Development) or Gherkin syntax, that describe the expected outcomes or effects of your code in terms of given, when, and then. You should also use comments and documentation to explain the purpose and context of your tests, especially when they are complex or unconventional.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Porin ?usti?

Freelance Software Engineer @ Toptal | Solving Problems and Building Scalable Solutions
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One important thing with tests is that they need to grow with your codebase. You need to be diligent to update your tests as you write new features or add new functionality to old features. If you don't do that you will have the false confidence that your codebase is tested but in fact it will be only partially tested full of potential bugs.

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What is the key to writing effective unit tests?

1

2

3

4

5

6

1 Define clear and specific test cases

2 Follow naming and organization conventions

3 Write isolated and independent tests

4 Write maintainable and reusable tests

5 Write readable and expressive tests

6 Here’s what else to consider

Computer Science

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What is the key to writing effective unit tests?

1

2

3

4

5

6

1 Define clear and specific test cases

2 Follow naming and organization conventions

3 Write isolated and independent tests

4 Write maintainable and reusable tests

5 Write readable and expressive tests

6 Here’s what else to consider

Computer Science

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