double[] vals = singleton().values().toDoubleArray();
assertThat(vals.length, equalTo(1));
assertThat(vals[0], closeTo(Math.PI));
DoubleRBTreeSet s = new DoubleRBTreeSet(simpleVector().values());
assertThat(s, equalTo(new DoubleRBTreeSet(new double[]{1.5, 3.5, 2})));
}