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edentext/tests/render-parity/README.md
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Steffen Becker 889f11cffc test: a committed corpus CI can read
Ten documents the docx lib authors directly, plus the ODT twin
LibreOffice converts each into, now live in tests/corpus/ instead of the
gitignored fixtures dir. corpus.test.ts asserts both formats of a
document read the same and that each survives our export and import
either way. The heading styles gained the outline level Word writes —
without it LibreOffice converts a heading to a paragraph that merely
carries the style, and the two formats disagreed.
2026-08-15 11:54:36 +02:00

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4.6 KiB
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# Render parity
Opens the same document in **LibreOffice** and in **the editor**, then compares the
resulting text layout. Everything else in `tests/` compares documents at the model
level (JSON → export → import); this leg is the only one that checks what a page
actually looks like.
```bash
npm run test:parity:fixtures # (re)generate the baseline .docx corpus
npm run test:parity # whole corpus
npm run test:parity -- path/to/file.docx --json report.json
```
Exit code 1 when any document differs. `--json` also dumps both sides' lines
(`y`, `x`, `x2` in mm, per page) — that dump is what you diagnose from.
## How it compares
| | reference | editor |
|---|---|---|
| render | `soffice --convert-to pdf` | Playwright Chromium, real app, real file input |
| read | `pdftotext -bbox-layout` (word boxes, pt) | `Range.getClientRects()` (word boxes, px) |
Both sides are normalized to mm from the top-left of each page, grouped into lines,
and compared as: page count → line count → line text → line position. Comparison is
whitespace-insensitive, because the spell-check decorations split text nodes
mid-word and the two engines needn't agree on word boundaries — only on what sits
on a line.
Reported differences are `pageCount`, `lineCount`, `lineBreak` (same line, different
words) and `position` (same words, off by more than `POS_TOL_MM`). Comparison of a
page stops at the first line-level divergence, since everything after it is noise.
## Prerequisites
```bash
apt-get install -y --no-install-recommends libreoffice-writer poppler-utils
npm install --no-save playwright-core && npx playwright-core install chromium
cp src/assets/fonts/*.ttf /usr/local/share/fonts/ && fc-cache -f
```
**The font step is not optional.** LibreOffice renders with system fonts; without
the repo's own TTFs installed it substitutes DejaVu for Liberation Serif and every
line breaks differently for a reason that is not a bug. With them, both engines
resolve Times New Roman → Liberation Serif, Arial → Liberation Sans, Calibri →
Carlito, Cambria → Caladea — the same files the editor bundles.
**But install only what LibreOffice does not already ship.** A second copy of a
family it bundles makes its render *non-deterministic*: it picks between the two
files per run — measured as `Carlito` against `Carlito-Regular` in the PDF's font
list — and their vertical metrics differ, so a page carrying a large-font heading
lands 1.85mm lower on some runs and a fixture's issue count swings by 40. The
browser side never needs the install: the app `@font-face`s its own copies. On a
macOS install `/Applications/LibreOffice.app/Contents/Resources/fonts/truetype/`
already holds Carlito, Caladea and Liberation, so **skip the `cp` there entirely**;
check any other platform with `fc-list | grep -ci carlito` before copying.
The runner starts `npm run dev` on port 5199 itself if nothing answers there.
## Fixtures
`make-fixtures.mjs` authors the baseline corpus with the `docx` lib **directly**,
not through `src/lib/export/docx.ts` — otherwise the corpus would test our exporter
against itself — and converts each document to its ODT twin with LibreOffice. It
writes them to **`tests/corpus/`, which is committed**: `tests/corpus.test.ts` reads
them at the model level (import → our own export → import) on every `npm test`, so
CI runs against documents this editor did not write. A run with no argument compares
that corpus *and* `fixtures/`, which stays gitignored — keep whatever real-world
files you test against there and local.
## Names stay local
A real-world document's name goes in no file, and a commit message names no document at
all — write the rule that changed and what it measured. `FINDINGS.md` is gitignored for
that reason.
Only this harness reads `fixtures/`. The directory is gitignored, so a `tests/unit/` test
reading it fails with `ENOENT` on a fresh clone; it zips its own document instead
(`docx-onoff.test.ts` — both importers take a `Uint8Array`, not a path), or reads
`tests/corpus/`, which is committed. CI greps for the read.
## Prerequisites, part two: Calibri Light
Word's default theme heading font. LibreOffice's substitution table knows Calibri but
not Calibri Light, so without an alias it falls to fontconfig's generic — DejaVu Serif,
a serif heading nothing else renders. Word substitutes plain Calibri, and so does the
editor (`global.css`), so give LibreOffice the same answer:
```xml
<!-- /etc/fonts/conf.d/30-calibri-light.conf, then fc-cache -f -->
<match target="pattern">
<test name="family"><string>Calibri Light</string></test>
<edit name="family" mode="prepend" binding="strong"><string>Carlito</string></edit>
</match>
```