We propose component customization failures by proposing the inter-class test technique between the black-box class, which represents the 'implementation', and the white-box class, which represents the 'interface' for component customization failures. Our proposed test technique is based on a fault injection technique where a fault is injected into the 'interface' of the component. For our technique, we first extract the component customization patterns and fault injection targets. We then define the fault injection operators, which are applied to the fault injection targets. Since the fault injection operators can cover all possible failures that can occur within component customization, the proposed testing technique is suitable for component customization testing.