assertEquals(Country.CANADA, bimap2.get(Currency.DOLLAR));
    assertEquals(bimap1, bimap2);
    bimap2.inverse().put(Country.SWITZERLAND, Currency.FRANC);
    assertEquals(Country.SWITZERLAND, bimap2.get(Currency.FRANC));
    assertThat(bimap1.get(Currency.FRANC)).isNull();
    assertFalse(bimap2.equals(bimap1));

    /* Test that it can be empty. */

 * (unless there are {@link Double#NaN NaN} values, see below); otherwise, the result is the average
 * of the values which would appear at the indexes floor(x) and ceil(x) weighted by (1-frac(x)) and
 * frac(x) respectively. This is the same definition as used by Excel and by S, it is the Type 7
 * definition in <a
 * href="http://stat.ethz.ch/R-manual/R-devel/library/stats/html/quantile.html">R</a>, and it is
 * described by <a