Jar's can be found here: https://bintray.com/robstoll/tutteli-jars/atrium/0.6.0
API Maturity: Almost Stable
Implementation Maturity: Development

I provide more or less a stable API for users of Atrium. Only the ReporterBuilder, which you use to build your own assertion verb might slightly change its API (so migrating will be just a few lines in one file).
There are most likely not any breaking changes in the API of the assertion functions/builders.
However, I do not provide yet a stable API for the core of Atrium -- this might affect you as well if you write your own assertion functions. It also affects you if you provide your own implementation of the core of Atrium.

New Features:

• isNumericallyEqualTo and isNotNumericallyEqualTo for BigDecimal
• isEqualIncludingScale and isNotEqualIncludingScale for BigDecimal
  => gives a hint in case of a failure where the assertion would have hold with isNumericallyEqualTo / isNotNumericallyEqualTo
• overload of toBe for BigDecimal which is deprecated, throws an UnsupportedOperationException and points the user to the above functions
• same same but different for the overload of notToBe for BigDecimal
• toBeWithErrorTolerance for floating point numbers (Float, Double, BigDecimal)
• isLessThan, isLessThanOrEquals etc. is now available for Comparable<T> and no longer only for Number
• containsRegex(...) as shortcut for contains.atLeast(1).regex(...)
• integrated contains not into the sophisticated contains assertion builder (for CharSequence and Iterable)
  => so that you see how many times it was contained when the assertion fails
• identification lambdas for Iterable with nullable types. For instance, listOf(null, 1).contains { toBe(1) } was not possible so far (only List<Int> was supported)
  • see API differences.md for examples.
• made AssertionPairFormatter configurable, one can now chose for instance a multi-line formatter instead of same-line (see README#your-first-assertion for an example)
• workaround for a Bug in Kotlin (please upvote it) which causes that returnValueOf cannot be used for methods with overloads.
• I generalised the DownCaster to a TypeTransformer which you can reuse by using the impl-function _typeTransformation. You find an example for Either in TypeTransformerSpec.
• I added a few issues with label help wanted so that you get an easy start to contribute to Atrium.

Breaking Changes:

• removed deprecated ReporterBuilder::withDetailedObjectFormatter

Deprecation:

• ReporterBuilder::withSameLineTextAssertionFormatter -> use the suggested replacement

Not included in this release yet

• sophisticated assertion builder for toBe with error tolerance for floating point numbers
• failure hint for toBe in conjuction with Float or Double
• simplify the creation of failure hints, make it reusable for users