src/main/java/org/fest/assertions/internal/Collections.java
public void assertContainsNull(Description description, Collection<?> actual) {
    assertNotNull(description, actual);
    if (!actual.contains(null)) {
      throw failures.failure(description, ShouldContainNull.shouldContainNull(actual));
    }
  }
public void assertContainsNull(Description description, Collection<?> actual) {
    assertNotNull(description, actual);
    if (!actual.contains(null)) {
      throw failures.failure(description, ShouldContainNull.shouldContainNull(actual));
    }
  }
public void assertContainsNull ( Description description , Collection < ? > actual ) { assertNotNull ( description , actual ) ; if ( ! actual . contains ( null ) ) { throw failures . failure ( description , ShouldContainNull . shouldContainNull ( actual ) ) ; } }
Asserts that the given {@code Collection} contains {@code null}.

@param description contains information about the assertion.
@param actual      the given {@code Collection}.
@throws AssertionError if the given {@code Collection} is {@code null}.
@throws AssertionError if the given {@code Collection} does not contain null.
Asserts that the given { @code Collection } contains { @code null } .