Add pager tests.

tests/test_pager.py

@@ -0,0 +1,74 @@
+"""Unit tests for pagination helpers in ``depicts.pager``.
+
+Covers page counting, slicing, page iteration, URL building, and Jinja init.
+"""
+
+from __future__ import annotations
+
+from depicts.pager import Pagination, init_pager, url_for_other_page
+from flask import Flask
+
+
+def _make_app() -> Flask:
+    """Create a minimal Flask app with a paging route."""
+    app = Flask(__name__)
+
+    @app.get("/items/<int:category_id>")
+    def items(category_id: int) -> str:  # noqa: ARG001 - used via request
+        # Return a URL for a different page while preserving args.
+        return url_for_other_page(5)
+
+    return app
+
+
+def test_pagination_basic_properties() -> None:
+    """Compute total pages and prev/next boundaries."""
+    p = Pagination(page=1, per_page=10, total_count=95)
+    assert p.pages == 10
+    assert p.has_prev is False
+    assert p.has_next is True
+
+    p2 = Pagination(page=10, per_page=10, total_count=95)
+    assert p2.pages == 10
+    assert p2.has_prev is True
+    assert p2.has_next is False
+
+
+def test_pagination_slice() -> None:
+    """Return the correct slice for a page window."""
+    items = list(range(25))
+    p = Pagination(page=2, per_page=10, total_count=len(items))
+    assert p.slice(items) == list(range(10, 20))
+
+
+def test_iter_pages_first_middle_last() -> None:
+    """Iterate pages with ellipses represented by ``None`` when skipping."""
+    p = Pagination(page=1, per_page=10, total_count=100)
+    pages = list(p.iter_pages())
+    # First page shows early pages, ellipsis, then tail pages
+    assert pages == [1, 2, 3, 4, 5, 6, None, 9, 10]
+
+    mid = Pagination(page=5, per_page=10, total_count=100)
+    # In the middle, defaults show all pages without gaps
+    assert list(mid.iter_pages()) == list(range(1, 11))
+
+    last = Pagination(page=10, per_page=10, total_count=100)
+    # Near the end, elide the early middle (3), keep a window around current
+    assert list(last.iter_pages()) == [1, 2, None, 4, 5, 6, 7, 8, 9, 10]
+
+
+def test_url_for_other_page_preserves_args_and_view_args() -> None:
+    """Build a URL for another page preserving args."""
+    app = _make_app()
+    with app.test_client() as client:
+        resp = client.get("/items/42?q=abc&page=3")
+        assert resp.status_code == 200
+        # The route returns the URL generated for page=5
+        assert resp.get_data(as_text=True) == "/items/42?q=abc&page=5"
+
+
+def test_init_pager_registers_jinja_helper() -> None:
+    """Register the helper in the Jinja environment globals."""
+    app = Flask(__name__)
+    init_pager(app)
+    assert app.jinja_env.globals["url_for_other_page"] is url_for_other_page