describe("peek functions",
{
    ee <- expect_equal

    test_that("peek and peekleft work correctly with deques", {
        d <- deque(1, 2, 3)
        ee(peek(d), 3)
        ee(peekleft(d), 1)
        ee(peek(deque()), NULL)
        ee(peekleft(deque()), NULL)
        ee(peek(deque(), default = 1), 1)
        ee(peekleft(deque(), default = 0), 0)
        ee(peek_at2(d), NULL)
        ee(peek_at2(d, default = 1), 1)
    })
})