@Test
    public void testInnerSelfJoin() {
        BiPredicate<Object, Object> TRUE = (t, u) -> true;

        assertEquals(asList(),
            Seq.of().innerSelfJoin(TRUE).toList());

        assertEquals(asList(
            tuple(1, 1),
            tuple(2, 2)),
            Seq.of(1, 2).innerSelfJoin((t, u) -> t == u).toList());

        assertEquals(asList(
            tuple(1, 2)),
            Seq.of(1, 2).innerSelfJoin((t, u) -> t * 2 == u).toList());
    }
@author Lukas Eder
@author Roman Tkalenko
jOOL/src/test/java/org/jooq/lambda/SeqTest.java