3.4Pagination Testing

Pagination is a common source of bugs: overlapping pages, missing items, incorrect totals.

def test_pagination_no_overlap(api):
    """Pages should not contain overlapping items."""
    r1 = api.get("/users?page=1&per_page=10")
    r2 = api.get("/users?page=2&per_page=10")
    ids1 = {u["id"] for u in r1.json()["items"]}
    ids2 = {u["id"] for u in r2.json()["items"]}
    assert ids1.isdisjoint(ids2), f"Overlapping IDs: {ids1 & ids2}"

def test_pagination_total_consistency(api):
    """Total count should be consistent across pages."""
    r1 = api.get("/users?page=1&per_page=10")
    r2 = api.get("/users?page=2&per_page=10")
    assert r1.json()["total"] == r2.json()["total"]

def test_pagination_all_items_covered(api):
    """Collecting all pages should yield exactly 'total' items."""
    all_ids = set()
    page = 1
    total = None
    while True:
        r = api.get(f"/users?page={page}&per_page=50")
        data = r.json()
        total = data["total"]
        items = data["items"]
        if not items:
            break
        all_ids.update(u["id"] for u in items)
        page += 1
    assert len(all_ids) == total

def test_pagination_boundary(api):
    """Request a page beyond the last page."""
    r = api.get("/users?page=99999&per_page=10")
    assert r.status_code == 200
    assert r.json()["items"] == []

def test_pagination_invalid_params(api):
    """Invalid pagination parameters should return errors."""
    r = api.get("/users?page=0&per_page=10")
    assert r.status_code == 400
    r = api.get("/users?page=1&per_page=0")
    assert r.status_code == 400
    r = api.get("/users?page=-1&per_page=10")
    assert r.status_code == 400