AssertJ assertions allMatch and doesNotContains on an empty list always returns true whatever the content of the predicate. Despite being correct, you should make explicit if you expect an empty list or not, by adding isEmpty()/isNotEmpty() before calling the assertion. It will justify the useless predicate to improve clarity or increase the reliability of the test.

This rule raises an issue when any of the methods listed are used without asserting that the list is empty or not.

Targetted methods:

Noncompliant Code Example

List<String> logs = getLogs();

assertThat(logs).allMatch(e -> e.contains(“error”)); // Noncompliant, this test pass if logs are empty!
assertThat(logs).doesNotContain("error"); // Noncompliant, do you expect any log?

Compliant Solution

List<String> logs = getLogs();

assertThat(logs).isNotEmpty().allMatch(e -> e.contains(“error”));
// Or
assertThat(logs).hasSize(5).allMatch(e -> e.contains(“error”));
// Or
assertThat(logs).isEmpty();

// Despite being redundant, this is also acceptable since it explains why you expect an empty list
assertThat(logs).isEmpty().doesNotContain("error");