test: 补充知识处理、检索与 Agent 回归用例

覆盖切块、向量检索、工具调用和历史预算；模型相关用例使用桩。

backend/tests/knowledge/test_pdf_limits.py

@@ -0,0 +1,75 @@
+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+A PDF's cost is its pages, not its bytes: each page is embedded, and a
+scanned one OCR'd. Past the page limit it is refused before any is read.
+"""
+
+import io
+from unittest.mock import patch
+
+import pytest
+from pypdf import PdfWriter
+
+from app.core.config import settings
+from app.knowledge.pdf_download import PdfTooLargeError
+from app.knowledge.pdf_limits import PdfRefused, PdfTooManyPages, check_page_count, count_pages
+
+
+def pdf_with_pages(n: int) -> bytes:
+    writer = PdfWriter()
+    for _ in range(n):
+        writer.add_blank_page(width=200, height=200)
+    out = io.BytesIO()
+    writer.write(out)
+    return out.getvalue()
+
+
+def test_the_pages_are_counted():
+    assert count_pages(io.BytesIO(pdf_with_pages(7))) == 7
+
+
+def test_a_file_path_is_counted_too(tmp_path):
+    path = tmp_path / "manual.pdf"
+    path.write_bytes(pdf_with_pages(4))
+    assert count_pages(str(path)) == 4
+
+
+def test_a_pdf_at_the_limit_is_accepted():
+    check_page_count(io.BytesIO(pdf_with_pages(3)), max_pages=3)
+
+
+def test_a_pdf_over_the_limit_is_refused_and_told_why():
+    with pytest.raises(PdfTooManyPages) as refused:
+        check_page_count(io.BytesIO(pdf_with_pages(4)), max_pages=3)
+    assert str(refused.value) == ("This PDF has 4 pages; the limit is 3. Upload the part you need, "
+                                  "or split it into smaller files.")
+
+
+def test_the_limit_comes_from_settings():
+    with patch.object(settings, "KB_PDF_MAX_PAGES", 2), pytest.raises(PdfTooManyPages):
+        check_page_count(io.BytesIO(pdf_with_pages(3)))
+
+
+@pytest.mark.parametrize("damaged", [b"%PDF-1.4 test pdf content", b"", b"not a pdf"])
+def test_one_that_cannot_be_counted_is_left_to_the_reader(damaged):
+    assert count_pages(io.BytesIO(damaged)) is None
+    check_page_count(io.BytesIO(damaged), max_pages=1)  # no refusal: the reader decides
+
+
+def test_both_limits_are_refusals_with_a_message_for_the_user():
+    too_big = PdfTooLargeError(25 * 1024 * 1024)
+    assert isinstance(too_big, PdfRefused)
+    assert str(too_big) == "This PDF is larger than 25 MB. Upload a smaller file, or split it into parts."