I stumbled upon the following snippet.
ArchRule myRule = classes()
.that().resideInAPackage("..core..")
.should().onlyBeAccessed().byAnyPackage("..controller..");
I wonder how I can negate this condition so, the test should check if the core package is not accessed by the controller package?
You can use ClassesShould.accessClassesThat(), which (as its JavaDoc suggests) usually makes more sense the negated way:
import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noClasses;
// ...
noClasses()
.that().resideInAPackage("..controller..")
.should().accessClassesThat().resideInAPackage("..core..");
You can also stick to classes() and use GivenClasses.should(…) or GivenClassesConjunction.should(…) with a flexible ArchCondition. For your case, it can be easily composed from pre-defined conditions and predicates:
import static com.tngtech.archunit.core.domain.JavaClass.Predicates.resideInAPackage;
import static com.tngtech.archunit.lang.conditions.ArchConditions.accessClassesThat;
import static com.tngtech.archunit.lang.conditions.ArchConditions.not;
import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.classes;
// ...
classes()
.that().resideInAPackage("..controller..")
.should(not(accessClassesThat(resideInAPackage("..core.."))));