edentext/docs/headless-testing.md

Headless browser testing

With no test suite, the way to verify rendering, layout, or interaction is to drive the live app in a headless browser. This container is linux arm64 (uname -m → aarch64) — the one gotcha. Use it for any check: pagination, list-marker/float layout, table sizing, header/footer, theme colors, image drag/resize, ODF round-trips, etc. PDF export is just one example.

• Don't use puppeteer / npx @puppeteer/browsers install chrome-headless-shell: they fetch an x86-64 Chrome that can't run here (rosetta error: failed to open elf at /lib64/ld-linux-x86-64.so.2). No arm64 chrome-headless-shell build exists.
• Use Playwright's Chromium (native arm64): npm install --no-save playwright-core && npx playwright-core install chromium → binary at ~/.cache/ms-playwright/chromium-*/chrome-linux/chrome. Playwright's install-deps host check errors out, but the libs install via apt: apt-get install -y libdbus-1-3 libnss3 libnspr4 libatk1.0-0 libatk-bridge2.0-0 libcups2 libdrm2 libxkbcommon0 libxcomposite1 libxdamage1 libxfixes3 libxrandr2 libgbm1 libasound2 libatspi2.0-0 libpango-1.0-0 libcairo2. Launch with playwright-core, executablePath at that binary, args: ['--no-sandbox'].

Then load npm run dev, inject a document into localStorage['edentext-doc'], reload, and read live DOM geometry (getBoundingClientRect, Range.getClientRects) or screenshot. This is the only way to exercise the editor's live ProseMirror NodeViews (e.g. the image node), which generateHTML can't reproduce. The debug/pagebreak-debug-*.json snapshots carry the live doc JSON, handy to inject.

For PDF-export repros specifically: replicate pdf.ts's clone + html2canvas(...) inside page.evaluate and read the canvas back as a PNG — capturing the real jsPDF doc.save() download tends to hang in headless. Inspect output PDFs with poppler-utils (apt-get install -y poppler-utils: pdftoppm, pdfimages, pdftotext).

The four committed browser runs

npm run test:smoke and npm run test:dom are these probes made permanent: both boot dist/ headless through tests/browser.mjs (preview server, checklist, pageerror collector) and fail on any uncaught page error. The DOM run keeps the pagination invariants of pass 4 below — one page count through a settle, a reload, a zoom, a page break and its undo — which is the only test src/lib/components/** has.

npm run test:layout and npm run test:monkey run against the dev server (Vite serves TypeScript, so a page imports src/ and tests/ modules directly). The layout run opens every corpus and showcase document plus LAYOUT_SEEDS fuzz seeds, holds the editor's page count against LibreOffice's PDF (soffice + pdfinfo, a page or a tenth of slack) and checks the rendered lines: none overlap, none sit in the page gap or past the sheet, none cross a single-section document's margins, no heading ends a page or column, nothing is wider than the page. A tab's box, a frame, a formula and the decor are not lines. It then holds the document against tests/layout/baseline.json, which records where each page starts and what the load cost: a page starting elsewhere is a layout change the run prints page by page, and a load over three times its recorded time is a regression. The baseline is keyed by engine and platform (line breaking is theirs) and LAYOUT_UPDATE=1 records it again — the answer to a deliberate change, never to a surprise. The monkey run replays MONKEY_OPS random keys and commands per seed (MONKEY_SEED, MONKEY_RUNS, MONKEY_DOC) on a corpus document — typing, formatting, lists, tables, notes, frames and columns — and checks after each: no uncaught error, a document its own schema accepts; at the end undo back to the opened file and redo forward, then Save As both formats, xmllint each against the schemas and read it back through the app's importer. A failing seed prints its last ops and keeps the file and both documents under the OS temp dir. Found so far: a note inserted in a text box or a text box in a note breaks the ODT's XML, and a table in a cell is dropped on save — both commands now refuse there; a page break inside a columns section, which the editor never shows and only DOCX writes, is now cleared as the blocks are wrapped; an .odt dropped every block of a list item after the first, and a header row that the table did not ask to repeat came back as ordinary cells. Then: setting one of a heading's two vertical margins zeroed the other in the .odt (LibreOffice pairs them); a page break before a list item reached neither file; a list item's further blocks lost their own alignment, spacing and line height in the .odt; a run could be subscript and superscript at once; and typing over a selection that spans two blocks let the contenteditable's own span land a whole CSS font stack, and a weight already saying bold, in the document. A list in a table cell shifted every body list item's own style by as many items as the cell held; and a heading inside a list item came back from the .odt as a paragraph. In a note's own text the .docx lost a formula, a ruby and a leading tab, and a heading in a table cell lost the margin it did not set; a list toggle could pull a note anchor into a text box, where the .docx dropped anchor and note without a word. A running-head or date field in a zone lost its own formatting in the .docx: the library's simple field writes a bare run. Typing over a selection spanning two header cells left a half-header first row, which no file keeps. One finding was the checker's own: libxml2's RelaxNG cannot match an element the ODF schema declares by name class inside a <text:span> (the statistic fields), so a formatted page count in a zone read as invalid — LibreOffice writes the same span. The run's own focus(pos) is snapped to the next text position: TipTap makes the selection wherever it is told, and Enter on a caret between two list items throws out of prosemirror — a place the view itself never puts one. In Firefox: a page break set inside a text box, which neither format keeps, so the same plugin now sweeps it from a table cell and a note body too; and the run's 1x1 PNG had a truncated IDAT, which only Firefox reports — the same broken bytes were in eleven fixtures. WebKit raises ResizeObserver loop completed with undelivered notifications as a page error — the text box refits the wrapper it observes, so the browser defers the rest of the round. That converging loop is the one message openApp drops. A comment over a line break rides the hardBreak too, which no file carries and the comment's own text runs keep — normalize skips the marks of an inline atom, the picture and the formula with it. Then the table run: promoting a cell to a header dropped every attr it had; a replace reaching into a table left the cell it landed in without its column weight, so redo (which replays the recorded step) restored one the edit itself had lost; a list toggle wrapped a table into a list item, where the .odt drops it; and a heading in a cell came back from the .docx carrying its size as direct formatting. A list's listStyleName is no longer compared: direct formatting on a marker makes the file keep the resolved automatic clone instead, and corpus.test.ts holds the plain round trip. Its marker char goes the same way — a list that lost its name carries the char the style drew, so both sides compare the drawn one, as the kind already did. Still open: a run set to the body's own font, in a columns section, kept its family on the held side once in four runs of the same seed chain — the flow rewrites such a document between frames, which is why that leg leaves the history unchecked too. Both header/footer zones go first, before the body ops can cut the document to one page. The run draws the two variant flags and the zone distances from the ribbon's Insert tab (Options) — with them on, a double-click on pages 1 to 3 in turn is one session per variant — and edits each with MONKEY_HF_OPS ops of the zone's own schema: runs, breaks, the insert bar's three fields, inline images, left by Done. 16-hf-variants brings the same six zones in through the import path instead. Then one flag is flipped while a zone is open, which ends the edit (App.svelte drops hfActive with it): the text typed before the flip has to be in the zones all the same. A zone is no part of the document, so the saved file is the only thing that reports on it: the round trip holds the zones the app's storage keeps against the ones the importer gives back, per section and per variant in play. Undo is not among the zone's keys — a pass falls into one history group, so a single Mod+Z would empty the zone and the round trip would compare nothing. Every run opens its document through input.file-input[accept*=".odt"]: the Insert tab carries a second .file-input for pictures, and a bare class selector picks whichever the ribbon happens to be showing.

BROWSER=chromium|firefox|webkit picks the engine (Chromium by default; the others via npx playwright-core install firefox webkit). CI runs both on all three, one per matrix leg, WebKit on macOS because only there its text shaping is Safari's. The engines are the ones behind build.target in vite.config.ts; a browser older than that target fails to parse the bundle and no run reaches it. Playwright's WebKit is the engine, not Safari: storage eviction, the install prompt and iOS input are outside the matrix.

Hunting for bugs the suite cannot see

npm run test:coverage says where to look: the logic modules are dense with tests, src/lib/components/** and App.svelte are at 0% — every bug found this way so far lived there. Give each probe a pageerror + console.error collector; that alone reports faults nobody predicted (two of six were found by clicking controls and reading the console).

Four passes, cheapest first:

1. Edges — junk in every edentext-* key, truncated/renamed/empty archives, a full localStorage, no IndexedDB, page-tall images, 400-section documents.
2. Breadth — click every control of every tab, watch only for uncaught errors.
3. Semantics — not "does it crash" but "is the answer right": reject a tracked change and compare against the original, TOC page numbers against the measured page of each heading, a numeric sort against 3/10/25. The worst bug found (a reject that ate the original text) crashes nothing.
4. Invariants — snapshot → act → undo → compare; page count stable over reloads; save → reopen; .docx and .odt of one corpus fixture giving identical counts.

Then repro minimally and take a stack trace off the dev server (sourcemaps) with Error.stackTraceLimit = 300 — the default ten frames stop above the cause.

Budget for false alarms. Three of four striking signals were the probe's own fault: Range.getClientRects also returns container rects (a layout checker built on it is noise), a stale button index reads as a dead control, and clicking .tiptap > p by index hits a different block once an edit has reflowed the document. Two more from the DOM run: TipTap's focus() lands on the next animation frame, so a key sent right after it is lost unless document.activeElement is awaited; and a page break before the empty last paragraph yields no page. Reproduce deterministically before touching any code.