@Test
public void getChildNodesInLevelOrderThrowsExceptionWhenMapNotContainsDn() {

    // given
    var childNodeDn = "child";
    var rootNode = new LdapUserNode()
            .setDirectReportsDn(List.of(childNodeDn));
    var expectedMessage = String.format("Child node with DN '%s' not found!", childNodeDn);
    // when / then
    assertThatThrownBy(() -> userUpdater.getChildNodesInLevelOrder(rootNode, Collections.emptyMap()))
            .isInstanceOf(IllegalArgumentException.class)
            .hasMessage(expectedMessage);
}