Foreword
The chapters presented here are a concise summary of more theoretical and high-level knowledge. It is recommended that you are familiar with writing very basic tests and mocks, and understand the concepts of polymorphism and dependency injection before reading on.
The ultimate goal of testing is to reduce costs and increase productivity. Development with testing is faster and safer than without.
Benefits of Testing
- Quality Assurance
- Automated Testing: Minimizes the need for human source code checking or manual testing, providing a cost-effective way to ensure continuous quality assurance and the correct functioning of software at all times.
- Early Feedback: Tests provide immediate bug feedback. This is especially true for detecting accidentally introduced bugs caused by code changes. The earlier bugs are detected, the cheaper they are to fix. This also eliminates the fear of introducing bugs when writing or modifying code.
- Bug Location Detection: Tests identify bug locations, saving debugging time.
- Testable Design
- Writing tests automatically forces developers to apply specific design best practices, resulting in a testable design that improves code and architecture testability, an important quality criterion.
- Documentation
- Always Up To Date: Tests serve as the most up-to-date form of code documentation, capturing the expected behavior of the production code in its current state or of a third-party library.
- Code Is Best Documentation: Good tests are quick and easy to understand because they are written in an expressive language that developers speak fluently. In addition, the actual documentation is often simply skipped over.
- Behavior Is Easier Than Implementation: Tests are a clearer representation of behavior than the implementation itself. Tests specify the input for a given code and assert the expected output, providing an intuitive understanding that's easier to grasp than the intricacies of production code. Simply put, what code does is easier to understand than how it does it.
What should be tested?
Every functionality you expect the software to provide at any moment. You should test:
- Functional Requirements
- High-level business use cases defined by the customer in project requirements. Tests are essentially requirements translated into code. And customer requirements are typically translated into acceptance tests.
- Non-Functional Requirements
- Lower-level technical use cases derived from high-level business use cases that are not directly visible to end users, but form the backbone of software functionality. This includes the expected behavior of the underlying components, modules and units.
- Border cases that could theoretically occur, such as maximum/minimum values, nulls, invalid input outside the permissible value range, zeroes, negative numbers, empty lists, values with special meaning, exceptions, etc.
- Performance requirements
- Security requirements
Related Topics
See also the articles on Test-Driven Development and Acceptance Testing.