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.
General
- Ultimate Goal of testing: Reduce costs and increase productivity. Development with testing is faster and safer than without.
- Definition 'Production Code': Code that provides functionality to meet project requirements.
- Definition 'Test Code': Often referred to as "tests", it is written to verify the correct functionality of the production code.
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 enforces design best practices, resulting in a 'testable design' and higher quality code. Good code and architecture are testable, and vice versa.
- Documentation
- Tests serve as the most current form of code documentation, capturing the expected behavior of the production code in its present state.
What should be tested?
Every functionality you expect the software to provide at any moment. You should test:
- Functional Requirements
- High-level use cases that are defined in project requirements. Tests are actually specification translated into code.
- Non-Functional Requirements
- Lower-level use cases derived from high-level project 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 functions, classes, modules, and components.
- Border cases that could theoretically occur, such as maximum/minimum values, nulls, invalid input, zeroes, negative numbers, empty lists, values with special meaning, exceptions, etc.
- Performance requirements
- Security requirements