answers {
    thirdArg<(String) -> Unit>().invoke("text")
}

answers {
    thirdArg<(String) -> Boolean>().invoke("text")
}

Unit cannot be cast to java.lang.Boolean

fun doSomething(
    data1: Int,
    data2: String,
    onSuccess: (String) -> Unit,
    onError: (Throwable) -> Unit
): Boolean

thirdArg<(String) -> Unit>

Type mismatch.
Required:
Boolean
Found:
Unit

answers {
    thirdArg<(String) -> Unit>().invoke("text")
    Unit
}

Boolean