 
     func testEmptyQueue() {
         var q = Queue<Int>()
-        assert(q.isEmpty)
-        assertNil(q.first)
-        assertNil(q.dequeue())
+        assertEmpty(q)
     }
 
     func testEnqueueDequeue() {

    func testSliceable() {
        var q: Queue = ["foo", "bar", "baz"]
        let index = q.startIndex.successor()
        println(q[index])
        let end = index.successor()
        var s = q[index..<end]

        assertEqual(s.dequeue(), "bar")
        assert(s.isEmpty)
        assertNil(s.dequeue())

        assertEqual(q.dequeue(), "foo")
        assertEqual(q.dequeue(), "bar")
        assertEqual(q.dequeue(), "baz")
    }
}

        q.enqueue(4)
        assertEqual(q.dequeue(), 3)
        assertEqual(q.dequeue(), 4)
        assertEmpty(q)
    }

    func testArrayLiteralConvertible() {
