Hamcrest的hasItems、contains和containsInAnyOrder有何不同？

Question

Collection<String> c = ImmutableList.of("one", "two", "three");
assertThat(c, hasItems("one", "two", "three");
assertThat(c, contains("one", "two", "three");
assertThat(c, containsInAnyOrder("one", "two", "three");

Answer 1

hasitems检查：

在检查的可迭代上连续传递至少产生一个项，该项等于指定的项中的相应项。

也就是说，它确保集合以任意顺序至少包含这些项。所以，

assertThat(c, hasItems("one", "two"));

assertThat(c, hasItems("three", "two", "one"));

assertThat(c, contains("one", "two")); // Fails

这将失败，因为剩下的“three”不匹配。

assertThat(c, contains("three", "two", "one")); // Fails

此操作失败，因为相应的项不匹配。

另一个相关的匹配器containsinanyOrder检查是否确实存在这些项，但以任何顺序：

assertThat(c, containsInAnyOrder("one", "two")); // Fails

assertThat(c, containsInAnyOrder("three", "two", "one"));