describe("add",
{
    ee <- expect_equal

    test_that("add.Container works correctly", {
        x <- container(1)
        ee(add(x, 2, x = 3), container(1, 2, x = 3))
        x_was_not_touched <- all.equal(x, container(1))
        expect_true(x_was_not_touched)

        ref_add(x, 2)
        ee(x, container(1, 2))
    })

    test_that("add works with sets", {
        x <- setnew(1)
        ee(add(x, 2, x = 3), setnew(1, 2, x = 3))
        x_was_not_touched <- all.equal(x, setnew(1))
        expect_true(x_was_not_touched)

        ref_add(x, 2)
        ee(x, setnew(1, 2))
    })

    test_that("add works with deques", {
        x <- deque(1)
        ee(add(x, 2, b = 3), deque(1, 2, b = 3))
        x_was_not_touched <- all.equal(x, deque(1))
        expect_true(x_was_not_touched)

        ref_add(x, 2)
        ee(x, deque(1, 2))
    })

    test_that("add.Dict works correctly", {
        d <- dict(a = 1)
        ee(add(d), d)
        ee(add(d, b = 2, x = 4), dict(a = 1, b = 2, x = 4))
        d_was_not_touched <- all.equal(d, dict(a = 1))
        expect_true(d_was_not_touched)

        ref_add(d, b = 2, d = 4)
        ee(d, dict(a = 1, b  = 2, d = 4))

        expect_error(ref_add(d, z = 9, b = 2), "name 'b' exists already")

        d_was_not_touched_upon_error <- all.equal(d, dict(a = 1, b = 2, d = 4))
        expect_true(d_was_not_touched_upon_error)

        expect_error(add(d, a = 2), "name 'a' exists already")
        expect_error(add(d, 2), "all elements must be named")
        expect_error(add(d, "a", 2), "all elements must be named")
    })

    test_that("add.dict.table works correctly", {
        dit <- dict.table(a = 1)
        ee(add(dit), dit)
        ee(add(dit, b = 2, x = 3), dict.table(a = 1, b = 2, x = 3))
        dit_was_not_touched <- all.equal(dit, dict.table(a = 1))
        expect_true(dit_was_not_touched)

        ref_add(dit, b = 2, c = 3)
        ee(dit, dict.table(a = 1, b = 2, c = 3))

        expect_error(add(dit, d = 4, 5), "all elements must be named")
        d_was_not_touched_upon_error <- all.equal(dit, dict.table(a = 1, b = 2, c = 3))
        expect_true(d_was_not_touched_upon_error)

        expect_error(add(dit, d = 4, a = 5, b = 6), "names 'a', 'b' exist already")
    })
})