rspec/rules/S5841/java/rule.adoc

== Why is this an issue?

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()++`` in addition to calling the assertion, or by testing the list's content further. 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 and without testing the content.


Targetted methods:

* ``++allMatch++``
* ``++allSatisfy++``
* ``++doesNotContain++``
* ``++doesNotContainSequence++``
* ``++doesNotContainSubsequence++``
* ``++doesNotContainAnyElementsOf++``


=== Noncompliant code example

[source,java]
----
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

[source,java]
----
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).doesNotContain("error").isEmpty();
// or test the content of the list further
assertThat(logs).contains("warning").doesNotContain("error");
----

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