Forall
forall is a property-testing combinator that constructs a property by applying a predicate to values generated from specified generators.
Functional Programming in Scala, Second Edition
Prop.forAll is a ScalaCheck API function that constructs a property by applying a predicate to values generated by a Gen.
- How it is used
- States generated-input laws as composable properties for property-based testing.
- How deep it goes
- Derives the polymorphic signature and implements execution with random inputs, result reporting, exceptions, and exhaustive-domain refinement.
- Examples
- Uses list reversal laws, Boolean properties, sorted lists, maximums, and a deliberately falsified reverse-equals-self claim.
- What you can do after
- Build it from scratch as a generator-driven test loop that returns passing or falsified results with diagnostics.
Read how Functional Programming in Scala, Second Edition explains forall →
Learn Haskell by Example
forAll is a QuickCheck combinator that attaches an explicitly supplied generator to a property test.
- How it is used
- Attaches a custom `Gen` generator to a QuickCheck property when test inputs require explicit control.
- How deep it goes
- Shows a complete generator and property pairing, then defers reusable generation to `Arbitrary` instances.
- Examples
- Uses a nonempty alphabet, bounded rotation count, and selected alphabet character to test `alphabetRot` closedness.
- What you can do after
- Apply it via QuickCheck to test a predicate against deliberately generated cases.
Related concepts
- property-based testinguses · Property-based testing is a software-testing technique that generates varied inputs and checks whether specified general properties of the software’s behavior hold across them.
- generatoruses · A generator is a computational component or construct that produces data or values from inputs, representations, context, or specified constraints.
- predicateuses · A predicate is a condition, expression, or function evaluated against an input or context to determine whether a specified criterion holds.
- existential typeused by · An existential type hides a concrete type while exposing values and operations guaranteed by constraints on that type.
- exceptionuses · An exception is a runtime signal or object representing an abnormal condition that interrupts ordinary program flow and may be handled or propagated.
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