testing - 处理测试中的代码重复

Question

在工作中，我尽可能多地实践测试驱动开发。我经常遇到的一件事是必须设置一堆 DTO，当它们的结构稍微复杂时，这就变成了很多代码。这样做的问题是代码通常很重复，我觉得它会分散测试的主要目的。例如，使用一个稍微做作和压缩的示例(在 java 中，jUnit + mockito):

class BookingServiceTest {

    private final static int HOUR_IN_MILLIS = 60 * 60 * 1000;
    private final static int LOCATION_ID = 1;
    @Mock
    private BookingLocationDao bookingLocationDao;

    @InjectMocks
    private BookingService service = new BookingService();

    @Test
    public void yieldsAWarningWhenABookingOverlapsAnotherInTheSameLocation() {
        // This part is a bit repetetive over many tests:
        Date now = new Date()
        Location location = new Location()
        location.setId(LOCATION_ID);

        Booking existingBooking = new Booking()
        existingBooking.setStart(now);
        existingBooking.setDuration(HOUR_IN_MILLIS);
        existingBooking.setLocation(location);
        // To here

        when(bookingLocationDao.findBookingsAtLocation(LOCATION_ID))
            .thenReturn(Arrays.asList(existingBooking));

        // Then again setting up a booking :\
        Booking newBooking = new Booking();
        newBooking.setStart(now);
        newBooking.setDuration(HOUR_IN_MILLIS / 2);
        newBooking.setLocation(location);               


        // Actual test...
        BookingResult result = service.book(newBooking);

        assertThat(result.getWarnings(), hasSize(1));
        assertThat(result.getWarnings().get(0).getType(), is(BookingWarningType.OVERLAPING_BOOKING));
    }

}

在这个例子中，设置并没有那么复杂，所以我不会考虑太多。然而，当需要更复杂的输入时，用于设置方法输入的代码往往会增加。在几个测试中使用类似的输入会加剧这个问题。将设置代码重构为单独的 TestUtil 类会有所帮助。那么问题是，在几个月后编写新测试时，很难找到这些实用程序类，从而导致重复。

1. 处理这种“复杂”DTO 以最大限度地减少测试设置中的代码重复的好方法是什么？
2. 您如何确保在使用类似代码时找到提取的 TestUtilities？
3. 我做错了吗？ :) 我是否应该以另一种方式构建我的软件以完全避免这种情况？如果是，怎么做？

Answer 1

有几种模式可以用来处理这种情况:

• > Object Mother
• > Test Data Builder

要深入讨论这些模式，请阅读优秀书籍 "Growing Object-oriented Software Guided by Tests"

测试数据生成器

为您希望促进实例化/设置的每个类创建一个构建器类。此类包含一系列方法，这些方法将正在构建的对象设置为特定状态。通常这些辅助方法会向构建器类返回一个实例，以便可以以流畅的方式链接调用。

// Example of a builder class:
public class InvoiceBuilder {
    Recipient recipient = new RecipientBuilder().build();
    InvoiceLines lines = new InvoiceLines(new InvoiceLineBuilder().build());
    PoundsShillingsPence discount = PoundsShillingsPence.ZERO;

    public InvoiceBuilder withRecipient(Recipient recipient) {
        this.recipient = recipient;
        return this;
    }

    public InvoiceBuilder withInvoiceLines(InvoiceLines lines) {
        this.lines = lines;
        return this;
    }

    public InvoiceBuilder withDiscount(PoundsShillingsPence discount) {
        this.discount = discount;
        return this;
    }

    public Invoice build() {
        return new Invoice(recipient, lines, discount);
    }
}

// Usage:
Invoice invoiceWithNoPostcode = new InvoiceBuilder()
    .withRecipient(new RecipientBuilder()
        .withAddress(new AddressBuilder()
            .withNoPostcode()
            .build())
        .build())
    .build();

对象母亲

对象母类是为不同的常见场景提供预制测试数据的类。

Invoice invoice = TestInvoices.newDeerstalkerAndCapeInvoice();

上面的例子是从 Nat Pryce's blog 借来的.