code: public void assertNotSame(Description description, Object actual, Object other) {
      if (actual == other) {
        String format = "expected not same:<%s>";
        throw failures.failure(description, new BasicErrorMessageFactory(format, actual));
      }
    }
docs: Asserts that two objects do not refer to the same instance.
  
  @param description the description of the <em>actual</em> object.
  @param actual the <em>actual</em> object.
  @param other the object to compare {@code actual} to.
  @throws AssertionError if the given objects refer to the same instance.