如何将复杂对象列表的成员与 Hamcrest 进行比较？

Question

假设我有一个 List<A> 其中

class A {
    private Integer val;
    private String name;
}

在我的测试用例中，我得到了这个列表，其大小和内容不确定。我想做的是比较我知道必须在列表中的两个列表元素的 val 字段与给定的 name 字段；

List<A> list = logic.getList();
assertThat(list, allOf(hasItems(hasProperty("name", equalTo("first")), 
                       hasItems(hasProperty("val", equalTo(***value from another member with name = "second"))));

我怎样才能做到这一点，或者这甚至可以通过 Hamcrest Matchers 实现？

Answer 1

编写自定义匹配器清理您的测试逻辑：

public class AMatcher extends TypeSafeMatcher<A> {
   A actual;
   public AMatcher(A actual) { this.actual = actual; }

   protected boolean matchesSafely(A a) {
      return a.equals(actual);  // or compare individual fields...
   } 

   public void describeTo(Description d) {
      d.appendText("should match "+actual); // printed out when a match isn't found.
   }
}

然后，使用它：

assertThat(list, allOf(new AMatcher(a1), new AMatcher(a2)));

或者，如果您不想创建 A 的实例来创建匹配器，请创建一个采用 'name' 和 'val' 参数的 AMatcher 构造函数。

Answer 2

您可以根据需要实施自定义 Matcher，例如检查某些具有名称的项目是否具有相同的值字段：

final class FooTest {

    static final class Foo {

        final int val;
        final String name;

        // all args constructor
    }

    // custom matcher
    static final class FoosHasSameValues extends TypeSafeMatcher<List<Foo>> {

        private final Set<String> names;

        // all args constructor

        FoosHasSameValues(final String... names) {
            this(new HashSet<>(Arrays.asList(names)));
        }

        @Override
        protected boolean matchesSafely(final List<Foo> items) {
            final List<Integer> values = items.stream()
                // filter only items with specified names
                .filter(i -> this.names.contains(i.name))
                // select only values
                .map(i -> i.val)
                .collect(Collectors.toList());
            if (values.size() != this.names.size()) {
                // matching failed if list doesn't contains all
                // needed items with names
                return false;
            }
            // check 
            return values.stream().distinct().limit(2).count() <= 1;
        }

        @Override
        public void describeTo(final Description description) {
            description.appendText("has items [")
                .appendValue(String.join(", ", this.names))
                .appendText("] with same values");
        }
    }

    @Test
    void testMatchers() throws Exception {
        MatcherAssert.assertThat(
            Arrays.asList(
                new Foo("first", 1),
                new Foo("second", 1),
                new Foo("third", 2)
            ),
            new FoosHasSameValues("first", "second")
        );
    }
}

如何将复杂对象列表的成员与 Hamcrest 进行比较？

How to compare members of a list of complex objects with Hamcrest?

java

junit

assert

matcher

hamcrest