问Java 8函数中的运行时异常

EN

public final class MainClass {
    public MainClass(
            final Function<InputModel, OutputModel> businessLogic,
            final Converter<Input, InputModel> inputConverter,
            final Converter<OutputModel, Output> outputConverter) {
        this.businessLogic = requireNonNull(businessLogic, "businessLogic is null.");
        this.inputConverter = requireNonNull(inputConverter, "inputConverter is null.");
        this.outputConverter = requireNonNull(outputConverter, "outputConverter is null.");
    }

    /**
     * Request Handler.
     */
    public Output handleRequest(final Input input) {
        requireNonNull(input, "input is null.");

        log.info("input request: {}", input);

        try {
            return inputConverter
                    .andThen(businessLogic)
                    .andThen(outputConverter)
                    .apply(input);
        } catch (final Exception ex) {
            throw new InternalServiceException(ex.getMessage(), ex);
        }
    }
}

public final class TestClass {

    @Mock
    private Function<InputModel, OutputModel> mockedBusinessLogic;

    @Mock
    private Converter<Input, InputModel> mockedInputConverter;

    @Mock
    private Converter<OutputModel, Output> mockedOutputConverter;

    private MainClass mainClass = new MainClass(mockedBusinessLogic, mockedInputConverter, mockedOutputConverter);

    @Test
    public void handleRequest_SHOULD_throwException_WHEN_inputConverter_throwsException() {
        final RuntimeException inputConverterException = new NullPointerException(EXCEPTION_MESSAGE);

        // what should I mock here? apply or convert.. apply for `Converter` seems to be deprecated.
        when(mockedInputConverter.convert(input))
                .thenThrow(inputConverterException);

        final Exception exception = assertThrows(
                InternalServiceException.class,
                () -> mainClass.handleRequest(input)
        );

        assertThat(exception.getMessage(), is(EXCEPTION_MESSAGE));
        assertThat(exception.getCause(), is(inputConverterException));
    }
}