Property-based testing
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
test domain rules over many generated inputs with jqwik.
Planned topics
- Example tests check chosen inputs; property tests state a rule that must hold for any valid input.
- jqwik generates many random inputs and shrinks failures to a minimal case.
- Good properties for Shop: total equals the sum of its lines; adding then removing an item restores the order; total is never negative.
- Define generators (
@Provide) that produce valid domain objects only. - Keep the seed from failures to reproduce them.
Draft outline details
Demonstration
@Property
void totalIsSumOfLines(@ForAll("orders") Order o) {
assertThat(o.total()).isEqualTo(o.lines().stream().mapToLong(Line::cents).sum());
}Check your understanding
What does shrinking do?
Show answer
Reduces a failing input to the smallest one that still fails.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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