fix(tests): isolate token chunker imports (#18018)

test/unit_test/rag/test_flow_chunker_import.py

@@ -0,0 +1,46 @@
+#
+#  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+#
+#  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.
+#
+
+import importlib
+import sys
+
+
+def test_token_chunker_imports_without_pdf_parser_symbols(pdf_parser_stub, monkeypatch):
+    monkeypatch.delattr(pdf_parser_stub, "RAGFlowPdfParser")
+    for module_name in [
+        "rag.flow.chunker",
+        "rag.flow.chunker.token_chunker",
+        "rag.flow.parser.pdf_chunk_metadata",
+    ]:
+        sys.modules.pop(module_name, None)
+
+    token_chunker = importlib.import_module("rag.flow.chunker.token_chunker")
+
+    assert callable(token_chunker._merge_text_chunks_by_token_size)
+
+    position_tag = "@@1\t10\t20\t30\t40##"
+    extracted_tags = []
+
+    class RuntimePdfParser:
+        @staticmethod
+        def extract_positions(value):
+            extracted_tags.append(value)
+            return [([0], 10.0, 20.0, 30.0, 40.0)]
+
+    monkeypatch.setattr(pdf_parser_stub, "RAGFlowPdfParser", RuntimePdfParser, raising=False)
+
+    assert token_chunker.extract_pdf_positions({"position_tag": position_tag}) == [[1, 10.0, 20.0, 30.0, 40.0]]
+    assert extracted_tags == [position_tag]