AssertJ 检查列表包含 X 项但均为空

Question

我查看了 AssertJ 示例 (https://github.com/joel-costigliola/assertj-examples/blob/master/assertions-examples/src/test/java/org/assertj/examples/IterableAssertionsExamples.java)，但找不到以下示例：-

断言列表的大小为 X，例如3
断言所有项目都是 null

例如

List<String> items= Arrays.asList(null, null, null);
assertThat(items).hasSize(3).containsOnlyNulls();

Note - containsOnlyNulls doesn't exist but this is essentially what I'm trying to test for. Can this be achieved in AssertJ?

Answer 1

您可以使用

// need to cast to String
assertThat(items).hasSize(3).containsOnly((String) null);

或

assertThat(items).filteredOn(item -> item == null).hasSize(3);

- 编辑 -

containsOnlyNulls 断言已添加到 AssertJ 3.9.0+

示例：

// assertion will pass
Iterable<String> items = Arrays.asList(null, null, null);
assertThat(items).containsOnlyNulls();

// assertion will fail because items2 contains a not null element
Iterable<String> items2 = Arrays.asList(null, null, "notNull");
assertThat(items2).containsOnlyNulls();

// assertion will fail since an empty iterable does not contain any elements and therefore no null ones.
Iterable<String> empty = new ArrayList<>();
assertThat(empty).containsOnlyNulls();

AssertJ 检查列表包含 X 项但均为空

AssertJ check list contains X items but are all null

assertj