Assertions comparing an object to itself are more likely to be bugs due to developer’s carelessness.
This rule raises an issue when the actual expression matches the expected expression.
Noncompliant code example
assertThat(actual).isEqualTo(actual); // Noncompliant
Compliant solution
assertThat(actual).isEqualTo(expected);
Exceptions
In a unit test validating the equals(...) and hashCode() methods, it’s legitimate to compare an object to itself. This
rule does not raise an issue for isEqualTo, assertEquals or hasSameHashCodeAs when the unit test name contains
(case insensitive): equal, hash_?code, object_?method. For example, in tests with the following names:
test_equals, testEqual, test_hashCode, test_hash_code, test_object_methods.
class MyClassTest {
@Test
void test_equals_and_hash_code() {
MyClass obj = new MyClass();
assertThat(obj).isEqualTo(obj); // Compliant
assertThat(obj).hasSameHashCodeAs(obj); // Compliant
}
}
