Why is this an issue?

There’s no reason to use literal boolean values or nulls in assertions. Instead of using them with assertEquals, assertNotEquals and similar methods, you should be using assertTrue, assertFalse, assertNull or assertNotNull instead (or isNull etc. when using Fest). Using them with assertions unrelated to equality (such as assertNull) is most likely a bug.

Supported frameworks:

Noncompliant code example

Assert.assertTrue(true);  // Noncompliant
assertThat(null).isNull(); // Noncompliant

assertEquals(true, something()); // Noncompliant
assertNotEquals(null, something()); // Noncompliant

Compliant solution

assertTrue(something());
assertNotNull(something());