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    Highlighting this section for programmers wanting testable, maintainable code that applies with or without PBT:

    Determinism: Make it possible to run the “system under test” deterministically, such that your tests can be reliable. This does not mean the code has to be pure, but you might need to stub or otherwise control side effects during your tests.

    No global state: In order for tests to be repeatable and independent of execution order, you might have to rollback database transactions, use temporary directories for generated files, stub out effects, etc.

    High cohesion: Strive for modules of high cohesion, with smaller units each having a single responsibility. Spreading closely related responsibilities thin across multiple modules makes the implementation harder to maintain and test.

    Low coupling: Decrease coupling between interface and implementation. This makes it easier to write tests that don’t depend on implementation details. You may then modify the implementation without modifying the corresponding tests.

    I find these guidelines universal for writing testable code in any programming language I’ve used professionally, regardless of paradigm or type system. They apply to both example-based and property-based testing.”