Add ArchUnit - a Java architecture test framework
Found it in the ThoughtWorks technology radar 2018 tool section:
@@ -166,6 +166,7 @@ This is a collection of static analysis tools and code quality checkers. Pull re
* [Haxe Checkstyle](https://github.com/HaxeCheckstyle/haxe-checkstyle) - A static analysis tool to help developers write Haxe code that adheres to a coding standard.
## Java
+* [ArchUnit](https://www.archunit.org/) - Unit test your Java architecture
* [Checker Framework](https://github.com/typetools/checker-framework/) - Pluggable type-checking for Java http://checkerframework.org/
* [checkstyle](https://github.com/checkstyle/checkstyle) - checking Java source code for adherence to a Code Standard or set of validation rules (best practices)
* [ckjm](http://www.spinellis.gr/sw/ckjm/) - calculates Chidamber and Kemerer object-oriented metrics by processing the bytecode of compiled Java files
