QuickTheories

What QuickTheories is

QuickTheories is a free property-based testing library for Java 8, described as a Java version of QuickCheck. It tests properties by generating random valid inputs, while its generator DSL supports common Java types and can constrain, combine, or convert generators for custom types. When a property fails, the library looks for smaller or simpler inputs that still produce the failure, without requiring custom shrinking code for each type. It reports the seed for a failing property, and developers can set a fixed seed for repeatable runs. QuickTheories works with JUnit, TestNG, or another test framework; its checkAssert method can use assertion libraries such as AssertJ and Hamcrest. The forAll API supports theories using one to four generated values. System properties configure seeds, example counts, and shrink attempts, while named profiles let users reuse configurations. An experimental coverage feature can guide searches toward new code paths, but may reduce performance by about 10% and interfere with JaCoCo or other coverage systems. It is licensed under Apache-2.0 and was produced at NCR Edinburgh as part of its graduate training program.