kotlin.test / kotlin.test / assertFalse assertFalse Common JVM JS Native 1.0 inline fun assertFalse ( message : String ? = null , block : ( ) -> Boolean ) : Unit (source) Asserts that the given block returns false . Common JVM JS Native 1.0 fun assertFalse ( actual : Boolean , message : String ? = null ) : Unit (source) Asserts that the expression is false with an optional message .