test: add PDF export endpoint coverage and run in CI (closes #72) (#82)

* add: initial implementation of unit test for pdf export

* fix: improvements for gaps

Author: bradjin8

.github/workflows/tests.yml

@@ -111,12 +111,10 @@ jobs:
         run: python -m unittest discover tests -v
 
       - name: Run pytest integration suite
-        # Pytest fixtures (tests/conftest.py) build a temp workspaceStorage
-        # and exercise the Flask routes via app.test_client(). Scoped to the
-        # new endpoint file because `pytest tests/` would also re-collect the
-        # 178 unittest.TestCase subclasses already run in the step above —
-        # ~2× the CI minutes for zero extra signal.
-        run: python -m pytest tests/test_api_endpoints.py -v --tb=short
+        # Pytest fixtures (tests/conftest.py) build a temp workspaceStorage and
+        # exercise Flask routes via app.test_client(). Only listed files — not
+        # `pytest tests/` — to avoid re-collecting unittest.TestCase classes above.
+        run: python -m pytest tests/test_api_endpoints.py tests/test_pdf_export.py -v --tb=short
 
       # ── PyInstaller desktop build (Windows only, once per workflow) ────────
       # Closes #44. Builds the onedir bundle and smoke-tests --help so the

tests/conftest.py

@@ -123,6 +123,15 @@ def workspace_storage() -> Generator[str, None, None]:
                 os.environ["CLI_CHATS_PATH"] = prior_cli
 
 
+@pytest.fixture
+def pdf_client():
+    """Flask test client for routes that do not read workspace storage (e.g. PDF export)."""
+    app = create_app()
+    app.config["TESTING"] = True
+    app.config["EXCLUSION_RULES"] = []
+    return app.test_client()
+
+
 @pytest.fixture
 def client(workspace_storage: str):
     """Flask test client bound to the temp workspace_storage fixture."""

tests/test_pdf_export.py

@@ -0,0 +1,126 @@
+"""Unit tests for POST /api/generate-pdf (api/pdf.py). Closes #72."""
+
+from __future__ import annotations
+
+from typing import Any
+from unittest.mock import patch
+
+PDF_MAGIC = b"%PDF-"
+
+
+def _post_pdf(
+    client,
+    *,
+    markdown: str = "",
+    title: str = "Chat",
+    json_data: dict[str, Any] | None = None,
+):
+    if json_data is not None:
+        return client.post(
+            "/api/generate-pdf",
+            json=json_data,
+            content_type="application/json",
+        )
+    return client.post(
+        "/api/generate-pdf",
+        json={"markdown": markdown, "title": title},
+        content_type="application/json",
+    )
+
+
+def _assert_pdf_response(response) -> None:
+    assert response.status_code == 200
+    assert response.content_type.startswith("application/pdf")
+    data = response.data
+    assert len(data) > 0
+    assert data.startswith(PDF_MAGIC)
+    # Trailing %%EOF is a minimal structural check (see tests/web-ui-qa-checklist.md).
+    assert b"%%EOF" in data[-1024:]
+
+
+class TestGeneratePdfHappyPath:
+    def test_normal_conversation_markdown(self, pdf_client):
+        md = """# Chat export
+
+## User question
+
+Please explain **recursion** in Python.
+
+- Base case
+- Recursive step
+
+```python
+def fact(n):
+    return 1 if n < 2 else n * fact(n - 1)
+```
+
+---
+"""
+        response = _post_pdf(pdf_client, markdown=md, title="Happy conversation")
+        _assert_pdf_response(response)
+        assert (
+            'attachment; filename="Happy conversation.pdf"'
+            in response.headers.get("Content-Disposition", "")
+        )
+
+    def test_empty_json_body_uses_defaults(self, pdf_client):
+        response = _post_pdf(pdf_client, json_data={})
+        _assert_pdf_response(response)
+        assert (
+            'attachment; filename="Chat.pdf"'
+            in response.headers.get("Content-Disposition", "")
+        )
+
+    def test_unsafe_title_characters_sanitized_in_filename(self, pdf_client):
+        response = _post_pdf(
+            pdf_client,
+            markdown="Hello",
+            title='bad<>:"/\\|?*name',
+        )
+        _assert_pdf_response(response)
+        assert (
+            'attachment; filename="bad_________name.pdf"'
+            in response.headers.get("Content-Disposition", "")
+        )
+
+
+class TestGeneratePdfEdgeCases:
+    def test_empty_markdown(self, pdf_client):
+        response = _post_pdf(pdf_client, markdown="", title="Empty chat")
+        _assert_pdf_response(response)
+
+    def test_very_long_content(self, pdf_client):
+        line = "This is a repeated paragraph for length testing. " * 20
+        md = "\n".join(f"Line {i}: {line}" for i in range(500))
+        response = _post_pdf(pdf_client, markdown=md, title="Long chat")
+        _assert_pdf_response(response)
+
+    def test_unicode_and_emoji_content(self, pdf_client):
+        md = (
+            "Smart quotes: “hello” and ’world’\n"
+            "Emoji: 🚀🔥 should not break PDF\n"
+            "Bullet • point\n"
+        )
+        response = _post_pdf(pdf_client, markdown=md, title="Unicode chat")
+        _assert_pdf_response(response)
+
+
+class TestGeneratePdfErrors:
+    def test_pdf_engine_failure_returns_500(self, pdf_client):
+        with patch(
+            "fpdf.fpdf.FPDF.output",
+            side_effect=RuntimeError("simulated failure"),
+        ):
+            response = _post_pdf(pdf_client, markdown="Hello", title="Fail")
+        assert response.status_code == 500
+        assert response.get_json() == {"error": "Failed to generate PDF"}
+
+    def test_invalid_export_payload_returns_500(self, pdf_client):
+        # Conversation IDs are resolved client-side (tabs API) before markdown is
+        # POSTed here. A non-string markdown field mimics a corrupted export request.
+        response = _post_pdf(
+            pdf_client,
+            json_data={"markdown": ["not", "a", "string"], "title": "Bad payload"},
+        )
+        assert response.status_code == 500
+        assert response.get_json() == {"error": "Failed to generate PDF"}