Fitness Functions
Fitness Functions are objective, automated tests or criteria used to measure and guide the architectural qualities of a software system, ensuring it continues to meet its goals as it evolves.
Goal
The primary goal of fitness functions is to provide a mechanism for continuously assessing and enforcing architectural decisions, ensuring the system remains robust, adaptable, and aligned with business objectives over time.
Context
There are so many architectural decisions to make when designing a system, and it's easy for the team to lose sight of the big picture. Fitness functions provide a way to codify and automate the evaluation of architectural decisions, ensuring that the system continues to meet its goals as it evolves.
Types
There are hundreds of 'ilities' that can be measured, but the most common fitness functions are:
| Type | Description |
|---|---|
| Modifiability | Measures the ease and speed of making changes to the system. |
| Scalability | Assesses the system's ability to handle increased loads efficiently. |
| Performance | Evaluates the system's response times and throughput under specific conditions. |
| Security | Tests the system against security benchmarks and vulnerability scans. |
| Availability | Measures uptime and the ability to recover from failures. |
Inputs
| Artifact | Description |
|---|---|
| User Stories | Detailed descriptions of the functionality, performance criteria, and interfaces needed for each component. |
| System Architecture | The high-level design of the system, including the components, interfaces, and interactions. |
Outputs
| Artifact | Description | Benefits |
|---|---|---|
| Automated Tests | A suite of automated tests that measure the system's compliance with architectural goals. | Ensures that architectural decisions are continuously enforced. |
Anti-patterns
- Over-Reliance on Manual Checks: Relying too heavily on manual reviews or checks for architectural compliance can lead to inconsistencies and oversights, as well as create a blocker in the path to production.
- One-Size-Fits-All Approach: Applying the same fitness functions across different contexts without considering the specific characteristics of each component or service.
- Ignoring Evolving Requirements: Failing to periodically review and adjust fitness functions as business needs and technologies change.