是否有一个Hamcrest匹配器来检查Collection是否为空还是null？

Question

是否有Hamcrest匹配器检查参数既不是空集合也不是空？

我想我总是可以使用

both(notNullValue()).and(not(hasSize(0))

但我想知道是否有更简单的方法,我错过了它.

Answer 1

您可以组合匹配器IsCollectionWithSize和OrderingComparison匹配器:

@Test
public void test() throws Exception {
    Collection<String> collection = ...;
    assertThat(collection, hasSize(greaterThan(0)));
}

• 为collection = null你得到

  java.lang.AssertionError: 
  Expected: a collection with size a value greater than <0>
      but: was null
  

• 为collection = Collections.emptyList()你得到

  java.lang.AssertionError: 
  Expected: a collection with size a value greater than <0>
      but: collection size <0> was equal to <0>
  

• 对于collection = Collections.singletonList("Hello world")测试通行证.

编辑:

刚刚注意到以下approch 无法正常工作:

assertThat(collection, is(not(empty())));

我想的越多,如果你想明确地测试null,我会推荐OP写的语句略有改动的版本.

assertThat(collection, both(not(empty())).and(notNullValue()));