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mcp-nextcloud/tests/unit/test_doc_classifier.py
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Chris CoutinhoandClaude Opus 4.8 044c1da750 feat: tier-0 document classifier in shadow mode
First step of the tiered document-processor effort (Deck #203): a cheap, local
pre-pass that recommends which extraction tier a PDF should start in, emitting
metrics WITHOUT changing routing yet -- so we gather per-tenant doc-mix data
before turning escalation on.

document_processors/classifier.py: classify_pdf(content) -> DocClassification.
Page-sampled (bounded on large docs), <~1s. Cheap signals only -- text-layer
chars, a text-quality score (catches the "Student 147" failure where a text
layer exists but is mashed/space-less junk), and image coverage. A page that is
mostly a raster image routes to OCR: its content (handwriting, stamps) isn't in
any text layer. Deliberately no get_drawings/graphics-density signal -- it's
slow on the exact pages it'd flag, the hotfix's graphics_limit already makes the
parse safe, and the (future) tier-1 quality gate catches lost tables.

Validated on the sample corpus: born-digital 2-col arxiv and a digital student
record -> fast (tier 1); a scanned+handwritten form -> ocr (tier 3).

Wiring (vector/processor.py): _shadow_classify runs the classifier on PDFs in a
worker thread, best-effort (never blocks/fails indexing), gated by the new
DOCUMENT_CLASSIFY_ENABLED setting. Metrics: astrolabe_document_classified_total
{recommended_tier}, astrolabe_document_classifier_flag_total{flag},
astrolabe_document_text_quality histogram.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-05 00:12:25 +02:00

87 lines
2.6 KiB
Python

"""Unit tests for the tier-0 document classifier.
Pins the routing decisions and the text-quality heuristic that drive which
extraction tier a PDF starts in:
* a clean born-digital PDF (text, no full-page images) -> ``fast`` (tier 1);
* a full-page-image scan -> ``ocr`` (tier 3), since handwriting/stamps aren't
in any text layer;
* the text-quality score distinguishes clean prose from mashed/space-less junk.
"""
import pymupdf
import pytest
from nextcloud_mcp_server.document_processors import classifier as clf
pytestmark = pytest.mark.unit
def _digital_pdf(
pages: int = 3, body: str = "Hello world this is clean text. "
) -> bytes:
doc = pymupdf.open()
for _ in range(pages):
page = doc.new_page(width=595, height=842)
page.insert_text((50, 60), body * 8)
data: bytes = doc.tobytes()
doc.close()
return data
def _full_page_image_pdf(pages: int = 2) -> bytes:
# A page whose entire area is a raster image -> looks scanned.
doc = pymupdf.open()
pix = pymupdf.Pixmap(pymupdf.csRGB, pymupdf.IRect(0, 0, 600, 850))
pix.clear_with(255)
img = pix.tobytes("png")
for _ in range(pages):
page = doc.new_page(width=595, height=842)
page.insert_image(page.rect, stream=img)
data: bytes = doc.tobytes()
doc.close()
return data
# --- text-quality heuristic --------------------------------------------------
def test_text_quality_clean_prose_scores_high():
assert clf._text_quality("the quick brown fox jumps over the lazy dog") > 0.8
def test_text_quality_mashed_tokens_scores_low():
# space-less / mashed layer (the "Student 147" failure mode)
mashed = "01322234567mobileoutstandingresilienceacademicachievementhurdles"
assert clf._text_quality(mashed) < clf.MIN_TEXT_QUALITY
def test_text_quality_empty_is_zero():
assert clf._text_quality("") == 0.0
# --- routing -----------------------------------------------------------------
def test_digital_pdf_routes_fast():
c = clf.classify_pdf(_digital_pdf())
assert c.recommended_tier == "fast"
assert c.ocr_page_fraction == 0.0
assert "image_heavy" not in c.flags
assert c.mean_text_quality > 0.8
def test_full_page_image_routes_ocr():
c = clf.classify_pdf(_full_page_image_pdf())
assert c.recommended_tier == "ocr"
assert c.ocr_page_fraction == 1.0
assert "image_heavy" in c.flags
# --- sampling bounds large docs ----------------------------------------------
def test_large_doc_is_sampled():
c = clf.classify_pdf(_digital_pdf(pages=120))
assert c.page_count == 120
assert c.sampled_pages <= clf.MAX_SAMPLED_PAGES