junit-quickcheck is a library that supports writing and running property-based tests in JUnit, inspired by QuickCheck for Haskell.
Property-based tests capture characteristics, or "properties", of the output
of code that should be true given arbitrary inputs that meet certain criteria.
For example, imagine a function that produces a list of the prime factors of
a positive integer n greater than 1. Regardless of the specific value of
n, the function must give a list whose members are all primes, must
equal n when all multiplied together, and must be different from the
factorization of a positive integer m greater than 1 and not equal to
n.
Rather than testing such properties for all possible inputs, junit-quickcheck and other QuickCheck kin generate some number of random inputs, and verify that the properties hold at least for the generated inputs. This gives us some reasonable assurance over time that the properties hold true for any valid inputs.
Documentation for the current stable version
import com.pholser.junit.quickcheck.Property;
import com.pholser.junit.quickcheck.runner.JUnitQuickcheck;
import org.junit.runner.RunWith;
import static org.junit.Assert.*;
@RunWith(JUnitQuickcheck.class)
public class StringProperties {
@Property public void concatenationLength(String s1, String s2) {
assertEquals(s1.length() + s2.length(), (s1 + s2).length());
}
}After browsing the documentation, have a look at some
examples in module junit-quickcheck-examples. These are built
with junit-quickcheck.