QuickTheories vs scalaprops

QuickTheories is a free, open-source property-based testing library for Java 8. It checks general properties and invariants by generating random valid inputs, then automatically searches for smaller or simpler values that still fail a property. The library reports the seed for a falsified property, and tests can use fixed seeds for deterministic runs. Its generator DSL creates common Java types, constrains values, and combines or converts generators for custom types. QuickTheories works with JUnit, TestNG, and other test frameworks; `checkAssert` supports assertion libraries such as AssertJ and Hamcrest. The `forAll` API handles theories over one to four generated values. System properties configure seeds, example counts, and shrink attempts, while named profiles can reuse settings. An experimental coverage feature targets new code paths, but may reduce performance by about 10% and interfere with JaCoCo or other coverage systems. The project uses the Apache-2.0 license.

Scalaprops is a free Scala property-based testing library for Linux. It generates test data, including non-constant scala.FunctionN values through Cogen, and lets each test define flexible parameters. Law checking is configurable, with identifiers that may use types other than String. Scalaz integration supplies laws plus Gen and Cogen instances for Scalaz types. Randomness uses an immutable generator rather than mutable scala.util.Random. Failed tests report their starting seed, which can be passed again with --seed= for repeatable runs. The README states support for Scala.js and Scala Native, using Mersenne Twister by default on JVM and Scala Native and Tiny Mersenne Twister on Scala.js. An sbt plugin adds scalapropsOnly selection by test class, method, and parameter. ScalapropsFramework and sbt are listed test runners. Parallel test execution is unsupported.