AssertJ：从提取列表 Returns 列表中检索第一项

Question

我正在尝试验证提取列表中的第一项。但是 AssertJ return 是 List 而不是来自 .first().

的预期对象

给定以下示例

public class AssertJTests
{
    @Test
    @DisplayName("Region Asia should only have one Country, Malaysia")
    public void assertRegion()
    {
        Region asia = new Region()
            .setName("Asia")
            .setCountries(Lists.newArrayList("Malaysia"));

        Consumer<Region> regionRequirement = region ->
            assertThat(region)
                .extracting(Region::getName)
                .containsOnly("Asia");

        Consumer<String> countryRequirement = country ->
            assertThat(country)
                .isEqualToIgnoringCase("Malaysia");

        assertThat(asia)
            .isInstanceOfSatisfying(Region.class, regionRequirement)
            .extracting(Region::getCountries)
            .hasSize(1)
            .first()
            .isInstanceOfSatisfying(String.class, countryRequirement);
}

    protected static class Region
    {
        private String name;

        private List<String> countries;

        List<String> getCountries()
        {
            return countries;
        }

        Region setCountries(final List<String> pCountries)
        {
            countries = pCountries;
            return this;
         }

         String getName()
         {
            return name;
         }

         Region setName(final String pName)
         {
             name = pName;
             return this;
          }
    }
}

我期待 .first() 到 return String，但 return 变成了 List<String>。出现以下错误：

java.lang.AssertionError: [List check first element] Expecting: <["Malaysia"]> to be an instance of: <java.lang.String> but was instance of: <java.util.ArrayList>

Answer 1

extracting 对于 Object 断言提取被测对象（此处为 asia）属性，从而产生 List 个提取的属性值。您的代码导致仅提取一个属性，因此结果是一个包含一个值的列表，事实证明该值也是一个列表，在 extracting 之后您最终得到的是一个 List一个元素是 asia.countries.

Answer 2

您可以使用 API 的 contains 和 extracting 方法断言。

例如：

@Test
public void oneDateShouldNotAfterAnotherDate() {
    
    Set<String> errors = ...;

    Assertions
            .assertThat(errors)
            .isNotEmpty()   
            .contains("OneDate_ShouldNot_After_AnotherDate");
    
    /*
        If you need assert specific field of object. Then:
     */
    Set<Error> errors = ...;

    Assertions
            .assertThat(errors)
            .isNotEmpty()
            .extracting("message")
            .contains("OneDate_ShouldNot_After_AnotherDate");
}

Answer 3

聚会晚了几年但是

.flatExtracting("countries")

应该对你有用

AssertJ：从提取列表 Returns 列表中检索第一项

AssertJ: Retrieving First Items From Extracting List Returns List Instead

java

assertj