function assertRectsEqual(expected, actual) {
  if (!GoogRect.equals(expected, actual)) {
    assertEquals(expected, actual);
  }
}
Produce legible assertion results. If two rects are not equal, the error
message will be of the form
"Expected <(1, 2 - 10 x 10)> (Object) but was <(3, 4 - 20 x 20)> (Object)"