nw-pbt-jvm

PBT JVM -- jqwik (Java/Kotlin) + ScalaCheck + ZIO Test

Framework Selection

Quick Start (jqwik)

import net.jqwik.api.*;

class SortProperties {
    @Property
    void sortPreservesLength(@ForAll List<Integer> list) {
        List<Integer> sorted = new ArrayList<>(list);
        Collections.sort(sorted);
        Assertions.assertEquals(list.size(), sorted.size());
    }
}
// Run: ./gradlew test (or mvn test)

Generator (Arbitrary) Cheat Sheet (jqwik)

@ForAll int x                          // any int
@ForAll @IntRange(min = 0, max = 99) int x
@ForAll @StringLength(min = 1, max = 50) String s
@ForAll @Size(min = 1, max = 10) List<Integer> list

// Custom provider
@Provide
Arbitrary<String> emails() {
    return Arbitraries.strings().alpha().ofMinLength(1).ofMaxLength(10)
        .map(name -> name + "@example.com");
}

// Combinators
Arbitraries.integers().between(0, 100)
Arbitraries.of("a", "b", "c")
Arbitraries.frequencyOf(Tuple.of(80, Arbitraries.integers()), Tuple.of(20, Arbitraries.just(0)))

// Combine
Combinators.combine(
    Arbitraries.strings().alpha().ofMinLength(1),
    Arbitraries.integers().between(1, 120)
).as((name, age) -> new User(name, age))

// Recursive
Arbitraries.recursive(
    () -> Arbitraries.of(JsonValue.NULL, JsonValue.TRUE),
    inner -> Arbitraries.maps(Arbitraries.strings(), inner).map(JsonValue::fromMap),
    5
)

Stateful Testing (jqwik)

@Property
void storeMatchesModel(@ForAll("storeActions") ActionSequence<MyStore> actions) {
    actions.run(new MyStore());
}

@Provide
ActionSequenceArbitrary<MyStore> storeActions() {
    return Arbitraries.sequences(
        Arbitraries.oneOf(
            Combinators.combine(Arbitraries.strings(), Arbitraries.integers())
                .as(PutAction::new),
            Arbitraries.strings().map(GetAction::new)
        )
    );
}

class PutAction implements Action<MyStore> {
    final String key; final int value;
    PutAction(String key, int value) { this.key = key; this.value = value; }
    @Override public MyStore run(MyStore store) { store.put(key, value); return store; }
}