How to Deal with Flaky Tests and Unreliable Test Environments

Causes, Solutions, Best Practices and Tips

Flaky tests are tests that sometimes pass and sometimes fail without any apparent reason. Unreliable test environments are test environments that are unstable, inconsistent, or prone to errors. Both of these problems can cause frustration, confusion, and wasted time for testers and developers.

Flaky tests and unreliable test environments can undermine the confidence and trust in the testing process and ultimately affect the quality and delivery of the software product. Therefore, it is important to identify, prevent, and fix these issues as soon as possible.

Personally, I have been dealt some serious blows from both issues, that’s why in this article, I discuss some of the common causes and solutions for flaky tests and unreliable test environments and share some best practices and tips to avoid them in the future.

Common causes of flaky tests

Flaky tests can have various causes, depending on the type, scope, and complexity of the tests. Some of the common causes are:

• Timing issues. This happens when the test depends on the execution time or order of the test steps, or when the test does not wait for the expected conditions or events to occur. For example, a test may fail if it tries to access an element that is not yet loaded, or if it expects a certain output that is delayed by a network call.
• External dependencies. This happens when the test relies on external factors that are outside the control of the test, such as third-party services, databases, APIs, or hardware devices. For example, a test may fail if the external service is down, slow, or returns unexpected data, or if the database connection is lost or corrupted.
• Non-deterministic behaviour. This happens when the test involves random, dynamic, or unpredictable elements that can affect the test outcome. For example, a test may fail if it uses a random number generator, or if it depends on the user input, system date, or environment variables.
• Test code bugs. This happens when the test code itself has errors, typos, or logical flaws that can cause the test to fail. For example, a test may fail if it has a wrong assertion, a missing parameter, or a syntax error.

Common causes of unreliable test environments

Unreliable test environments can also have various causes, depending on the configuration, setup, and maintenance of the test environments. Some of the common causes are:

• Inconsistent test data. This happens when the test data is not aligned with the test scenarios, or when the test data is not refreshed, cleaned, or isolated properly. For example, a test may fail if it uses outdated, invalid, or conflicting data, or if it modifies the data that is shared by other tests.
• Configuration drift. This happens when the test environment settings or parameters are not consistent with the production environment, or when the test environment is not updated or synchronized regularly. For example, a test may fail if it uses a different version, library, or framework than the production environment, or if it runs on a different operating system, browser, or device than the intended target.
• Resource contention. This happens when the test environment resources are insufficient, overloaded, or shared by multiple tests or users. For example, a test may fail if it runs out of memory, disk space, or network bandwidth, or if it competes with other tests or users for the same resource.

Solutions for flaky tests and unreliable test environments

Flaky tests and unreliable test environments can be challenging to diagnose and fix, as they may not be reproducible or traceable easily. However, there are some general steps and strategies that can help to resolve these issues effectively. These are:

• Identify and isolate the problem. The first step is to find out which tests are flaky, and which test environments are unreliable, and isolate them from the rest of the test suite or test pipeline. This can be done by using tools such as test reports, logs, dashboards, or analytics, or by manually running the tests multiple times under different conditions or settings. This can help to narrow down the scope and source of the problem and prevent it from affecting other tests or environments.
• Analyze and debug the problem. The next step is to analyze and debug the problem and identify the root cause and the possible solution. This can be done by using tools such as debuggers, breakpoints, or print statements, or by inspecting the test code, test data, test environment, or test output. This can help to understand the logic and behaviour of the test and pinpoint the exact location and reason of the failure.
• Fix and verify the problem. The final step is to fix and verify the problem and ensure that the test is stable and reliable. This can be done by applying the appropriate solution, such as modifying the test code, test data, test environment, or test configuration, or by using techniques such as retries, timeouts, waits, mocks, stubs, or spies. This can help to eliminate the flakiness or unreliability of the test and confirm that the test passes consistently and correctly.

Best practices and tips to avoid flaky tests and unreliable test environments

Flaky tests and unreliable test environments can be costly and time-consuming to deal with, and can have a negative impact on the testing quality and efficiency. Therefore, it is better to prevent them from happening in the first place, or at least minimize their occurrence and severity. Here are some best practices and tips to avoid flaky tests and unreliable test environments:

• Design and write good tests. A good test is a test that is clear, concise, consistent, and complete. It should follow the testing principles and standards, such as the AAA pattern (Arrange, Act, Assert), the FIRST principles (Fast, Independent, Repeatable, Self-validating, Timely), and the SMART criteria (Specific, Measurable, Achievable, Relevant, Time-bound). It should also follow the testing best practices and guidelines, such as the test pyramid, the test automation framework, and the test naming convention. A good test can help to reduce the complexity and ambiguity of the test, and improve the readability and maintainability of the test code.
• Use reliable and realistic test data. A reliable and realistic test data is a test data that is valid, accurate, and representative of real-world scenarios and expectations. It should be generated, managed, and maintained properly, using tools such as test data generators, test data factories, or test data management systems. It should also be refreshed, cleaned, and isolated regularly, using techniques such as test data reset, test data cleanup, or test data sandboxing. May I add here that your browser cache should always be cleared before you start a new test. A reliable and realistic test data can help to ensure the consistency and relevance of the test, and avoid the errors and conflicts caused by the test data.
• Maintain and monitor test environments. A well-maintained and well-monitored test environment is a test environment that is stable, consistent, and aligned with the production environment. It should be configured, set up, and updated regularly, using tools such as configuration management, infrastructure as code, or continuous integration. It should also be monitored and measured regularly, using tools such as performance monitoring, resource utilization, or health checks. A well-maintained and well-monitored test environment can help to ensure the availability and reliability of the test, and avoid the failures and discrepancies caused by the test environment.
• Review and refactor test code. A well-reviewed and well-refactored test code is a test code that is clean, simple, and efficient. It should be reviewed and verified regularly, using tools such as code reviews, code analysis, or code coverage. It should also be refactored and improved regularly, using techniques such as code smells, code duplication, or code complexity. A well-reviewed and well-refactored test code can help to ensure the quality and performance of the test, and avoid the bugs and flaws caused by the test code.

TL;DR

Flaky tests and unreliable test environments are common and serious problems that can affect the testing process and the software product. They can be caused by various factors, such as timing issues, external dependencies, non-deterministic behaviour, test code bugs, inconsistent test data, configuration drift, or resource contention. They can be solved by following some general steps and strategies, such as identifying and isolating the problem, analyzing and debugging the problem, fixing and verifying the problem. They can also be avoided by following some best practices and tips, such as designing and writing good tests, using reliable and realistic test data, maintaining and monitoring test environments, reviewing and refactoring test code.

By dealing with flaky tests and unreliable test environments effectively, we can improve the stability and reliability of our tests, and enhance the confidence and trust in our testing process. This can ultimately lead to a better quality and delivery of our software product.

I hope you find this article helpful. Let me know in the comments.