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