Property-Based Testing
Property-based testing, also known as generative testing, describes properties that should be true for all valid test scenarios. A property-based test consists of a method for generating valid inputs (also known as a generator), and a function that takes a generated input. This function combines a generator with the function under test to decide whether the property holds for that particular input. With property-based testing, we automatically generate data across a wide search space to find unexpected problems.
Imagine a room-booking application. We should allow users to search for rooms suitable for families. Such rooms should have at least two beds. We could have a function that returns only those rooms that have at least two beds. With unit testing, we would need to write scenarios for the following:
- Zero beds
- One bed
- Two beds
- Three beds
- Four beds
- Five beds
- And other scenarios
If we wanted to test rooms with 20 beds...
