Testing

Kt-Math aims at giving the same results as java.math on every platform, exceptions included. Rather than hand-picked expectations, most of its tests are differential: they run the same operations on Kt-Math and on java.math, and compare the outcomes.

On the JVM

TestAgainstJavaMath runs every operation of the interfaces, on many inputs (small and huge numbers, edge cases, every rounding mode), both on the Kotlin port and on java.math, and compares results and exception types. CI runs it on Java 8, 17, 21 and 25.

On JavaScript and Kotlin/Native

java.math isn't available there, so the JVM computes the expected outcomes once: generateDifferentialCases runs the named operations of DifferentialOps on java.math and writes cases and outcomes to a file, which the JS and native tests replay on Kt-Math. CI runs them on Node.js, Linux, Windows, macOS and the iOS, watchOS and tvOS simulators.

BigDecimalMath and BigRational are compared with big-math itself in the same way.

Usage tests

The API is also exercised as users of each language see it: in Java (JUnit), plain JavaScript (Node's test runner, on the npm package as published) and C (against the Kotlin/Native shared library). The examples of this website are quoted from those tests.