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  • Test Heroes Consulting

The 6 Principles of Test Automation: Building Quality and Reliable Software

In software development, tests play a vital role in ensuring that code functions as intended. Traditionally, tests were conducted manually, similar to automobile crash tests that verify the safety of vehicles. However, manual testing is expensive and time-consuming, often causing delays in product launches. To overcome these challenges, automated software testing has emerged as a cost-effective solution. By implementing test automation, developers can receive continuous feedback, detect issues early in the production cycle, and achieve quicker iterations, resulting in improved design, higher quality, and safer product launches. In this article, we will explore six key principles that can help developers navigate the world of test automation and enhance their software development process.

Principle 1: Tests should improve quality

Quality is a subjective concept that can be challenging to define numerically. Nevertheless, the software industry employs various metrics to measure quality, including the number of defects, code coverage, CI error rate, and test failure rate. Automated tests play a crucial role in improving these quality metrics. By running hundreds or thousands of tests continuously, automated testing can identify defects before they reach the production stage. It alerts developers to potential problems and ensures that the system aligns with user expectations. With the ability to capture defects early, developers can create a solid design foundation that promotes quality.

Principle 2: Tests should reduce the risk of failures

While code review and pair programming are valuable practices, they cannot guarantee the absence of bugs or errors. To reliably identify and mitigate risks, developers must build a comprehensive automated test suite. Automated tests offer the advantage of examining the entire application, catching errors before they cause any harm. They also help in identifying regressions and enable the application to be tested across different devices and environments, which would be prohibitively expensive to achieve manually. Additionally, automated tests can scan the project's codebase for errors and security vulnerabilities, even when third-party dependencies are involved, reducing risks further.

Principle 3: Tests help in understanding the code

Developers often encounter situations where they struggle to comprehend their own code or code written by others. Reading tests can be an excellent way to understand a system, as they serve as practical examples of how things work. By referring to the test suite, developers can gain insights into how an API should respond or explore specific functionalities. Tests also provide the flexibility to comment out certain lines of code to identify which test fails or experiment with code improvements and refactorings. The knowledge gained from tests enhances developers' understanding of the system, leading to better code comprehension and maintenance.

Principle 4: Automated tests should be easy to write

While some tests start as manual tests and later transition to automation, this approach often results in complex, slow, and cumbersome tests. The ideal scenario occurs when tests and code work synergistically, encouraging developers to produce modular code that simplifies and granularizes the tests. Test simplicity is crucial to avoid the creation of tests for tests or introducing failures within the test suite, which can lead to false positives and flakiness. Many testing frameworks employ Domain Specific Languages (DSLs) to define tests using plain English. These frameworks, such as Cucumber with its Gherkin language, promote code readability and separate the production code from the tests. Adhering to fundamental principles, including having one assertion per test, keeping code separate from tests, maintaining test independence, minimizing test overlap, and preserving code encapsulation, contributes to effective and maintainable automated tests.

Principle 5: Tests should be easy to run

For automated tests to be efficient, developers should be able to run them seamlessly and without relying on extensive checklists or manual interventions. Modern developer tools, including sophisticated IDEs, offer features that automatically detect file changes and initiate the test suite. Similarly, command-line programs like nodemon, live reload, fswatch, or testmon can provide the same automation capabilities. To facilitate easy test execution, certain conditions must be met. Tests should be idempotent, ensuring that they do not have side effects and can be safely run multiple times. Determinism is essential, where tests consistently produce the same results given the same inputs. Test independence enables developers to run tests in any order, while lightweight tests execute within a reasonable time on the developer's machine. Granularity allows developers to run specific portions of the test suite. Furthermore, integrating testing into the continuous integration pipeline ensures that tests are run automatically with each commit, providing instant feedback and early detection of failures.

Principle 6: An automated test suite should require low maintenance

By adhering to the previous principles, developers can achieve a test suite that requires minimal maintenance. Test automatization allows machines to handle the repetitive and tedious aspects of testing, enabling developers to focus on creative and rewarding work. A positive feedback loop is established when tests are easy to write and frequently executed. Developers appreciate the value that automation brings to their work, motivating them to write and maintain tests effectively. Although periodic maintenance is necessary to keep the test suite in good shape, it should be minimal. Recommendations for maintaining the test suite include writing an optimal number of tests, choosing appropriate test types based on the situation, ensuring test reliability and avoiding flaky tests, and prioritizing test speed to prevent delays in development.


The misconception that testing is expensive stems from an inadequate understanding of the costs associated with poor quality. Bugs and defects, when left unaddressed, can have a substantial impact on the value of a product. However, building and refining an automated test suite can serve as a foundation for exceptional software quality and an excellent developer experience. By implementing the six principles of test automation outlined in this article, developers can improve quality metrics, reduce the risk of failures, enhance code comprehension, simplify test writing, streamline test execution, and achieve a low-maintenance test suite. Embracing these principles will empower developers to deliver outstanding software that meets user expectations while ensuring a smooth and efficient software development process.

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