### Question:
ActivityDataIOEditorWidget implements ActivityDataIOEditorWidgetView.Presenter { public void removeAssignment(final AssignmentRow assignmentRow) { view.getAssignmentRows().remove(assignmentRow); if (view.getAssignmentRows().isEmpty()) { view.setNoneDisplayStyle(); } }  @PostConstruct void init(); @Override void handleAddClick(); void setIsSingleVar(final boolean isSingleVar); void setVariableType(final VariableType variableType); void setAllowDuplicateNames(final boolean allowDuplicateNames,
                                       final String duplicateNameErrorMessage); void removeAssignment(final AssignmentRow assignmentRow); void setData(final List<AssignmentRow> assignmentRows); List<AssignmentRow> getData(); VariableType getVariableType(); void setDataTypes(final ListBoxValues dataTypeListBoxValues); void setProcessVariables(final ListBoxValues processVarListBoxValues); void setDisallowedNames(final Set<String> disallowedNames,
                                   final String disallowedNameErrorMessage); boolean isDuplicateName(final String name); boolean isMultipleInstanceVariable(final String name); void setIsVisible(final boolean visible); Widget getWidget(); void setReadOnly(final boolean readOnly);  }### Answer:
@Test public void testRemoveAssignmentEmpty() { widget.removeAssignment(assignmentRowOne); widget.removeAssignment(assignmentRowTwo); widget.removeAssignment(assignmentRowThree); verify(view).setNoneDisplayStyle(); assertEquals(0, view.getAssignmentRows().size()); }
@Test public void testRemoveAssignmentNonEmpty() { widget.removeAssignment(assignmentRowOne); widget.removeAssignment(assignmentRowThree); verify(view, never()).setNoneDisplayStyle(); assertEquals(1, view.getAssignmentRows().size()); assertEquals(assignmentRowTwo, view.getAssignmentRows().get(0)); }