2026-10-26 06:40:21 +01:00
1 changed files with 123 additions and 91 deletions
@@ -1,114 +1,146 @@
-# Responsive-layout harness
+# The viewport test
-Automated verification of the responsive layout that landed in #5. Run it with:
+`make frontend-viewport-test` checks the page's layout at several window widths
 in a real browser:
 ```bash
 make frontend-viewport-test
 ```
-It builds `dist/`, serves it from the same digest-pinned `nginx` image and the
+First it runs the unit tests. Then it builds the page into `dist/`. It serves
-same `configs/nginx.conf` the shipping container uses, drives a digest-pinned
+`dist/` with the nginx image and the `configs/nginx.conf` that the Docker image
-headless Chrome against it over CDP, and asserts on computed layout at every
+ships. Before the browser starts, it fetches `/` and `/no-such-page`, which
-viewport width derived from the app's own CSS. Screenshots land in
+nginx answers with the page. Both must carry `Cache-Control: no-cache` and a
-`tmp/viewport/` alongside a `results.json`; they are artifacts for a human to
+`Content-Security-Policy` header. Then it starts a headless Chrome in a
-look at when something fails, not the evidence. The assertions are the evidence.
+container and opens the page in it at each width. For each width it measures the
 layout inside the page and checks the measurements in Node. The checks decide
 pass or fail. Screenshots and a `results.json` land in `tmp/viewport/`, for a
 person to look at when a check fails.
-The target is deliberately outside `make check`: it takes minutes, and
+The test is not part of `make check`: it takes minutes, and `make test` has to
-`make test` has to stay under 60 seconds.
+finish in under 60 seconds.
-## How the widths are chosen
+## The widths
-Not from a list of phone models. `viewports.js` parses the `@media` conditions
+The breakpoints are read from the page's own files. `viewports.js` reads the
-out of `web/src/styles.css` and scans `web/src/main.js` and `web/index.html` for
+`min-width` and `max-width` conditions out of the `@media` blocks in
-Tailwind responsive prefixes, then tests every breakpoint it finds at one pixel
+`web/src/styles.css`. It also looks in `web/src/main.js` and `web/index.html`
-below it, exactly on it, and one pixel above it. A generic 375px "phone" test
+for Tailwind's responsive class prefixes, such as `md:`, and takes their
-sails straight past an off-by-one at a media query boundary; `max-width: 768px`
+breakpoints. Each breakpoint is tested at one pixel below it, exactly on it, and
-matches _at_ 768, and the sweep pins down which side of that line each layout is
+one pixel above it. Today the CSS has one breakpoint, `max-width: 768px`, and no
-on.
+responsive prefix is used.
-Nothing hardcodes 768. Add a second media block or start using `md:` classes and
+A `max-width: 768px` block matches at 768 pixels. Testing both sides of each
-the new breakpoint is covered without this directory being touched. The app is
+breakpoint catches a layout that switches one pixel too early or too late. A
-desktop-first today (all narrow rules live in `max-width` blocks); a
+second media block, or a first `md:` class, is covered without a change to this
-`min-width`-only, mobile-first set is handled as its inverse, and a set that
+directory.
 mixes the two makes the run fail loudly rather than test the right widths with
 the wrong expectation. Four further viewports are fixed anchors, each with a
 stated reason: a 320px floor, a 1280px desktop baseline, and two phone-landscape
 sizes straddling the breakpoint for the rotation case.
-## What it asserts
+The page is desktop-first: the wide layout is the default, and every narrow rule
 is in a `max-width` block. So a width is expected to show the narrow layout when
 one of those blocks matches it. A page with only `min-width` blocks would be
 read the other way round. A page that mixes the two kinds fails the run with a
 message, because the right expectation for each width can no longer be read from
 the breakpoints alone.
- **app-rendered** — enough host rows exist and enough of them show a numeric
+Four more widths are fixed, each for a stated reason:
  latency. This one exists so the rest cannot pass vacuously against a blank
  page.
 - **no-horizontal-overflow** — `documentElement.scrollWidth` fits the layout
  viewport, with the widest offending element named.
 - **nothing-past-viewport-edge** — no visible element's box extends past the
  viewport edge.
 - **no-clipped-text** — nothing hides text behind `overflow: hidden`. Deliberate
  ellipsis truncation (Tailwind's `truncate`, used on host names and URLs) is
  excluded: it is a design choice, not breakage.
 - **tap-targets-44px** — every interactive control is at least 44x44 CSS px on
  touch viewports, _and_ each selector in the control list matched at least the
  number of visible elements it declares: one of each single control, and one
  pin button per WAN host row. The second half is what stops the check passing
  vacuously: with size alone, a renamed class would take its controls out of the
  measured set and the check would report "all 0 controls are at least 44x44"
  and pass. See below.
 - **host-rows-stacked / host-rows-side-by-side** — the rows genuinely reflow.
  Computed `flex-direction` _and_ the actual geometry are checked, and in the
  narrow layout the info block and the sparkline must each occupy essentially
  the full row width. A row that merely shrank its 420px column would fail.
 - **probing-still-runs / gateway-detection-still-runs** — narrow viewports keep
  probing and keep detecting the gateway. The mobile early-return path proposed
  in #8 was rejected; this is what would catch it coming back.
-### The tap-target threshold
+- 320 by 568 pixels: the narrowest width still in common use
 - 667 by 375 pixels: a phone in landscape, inside the narrow layout
 - 844 by 390 pixels: a large phone in landscape, in the wide layout but still a
  touch device
 - 1280 by 800 pixels: a desktop window
-44x44 CSS px. That is the figure in Apple's Human Interface Guidelines and in
+Every width but 1280 by 800 is tested as a touch device.
 WCAG 2.2 SC 2.5.5 "Target Size (Enhanced)". WCAG 2.2 SC 2.5.8 (level AA) sets a
 lower 24x24 floor, but that floor comes with a spacing exception these controls
 do not qualify for — the pin buttons sit directly against the host name they
 belong to.
-## Determinism
+## The checks
-The browser container runs on an `--internal` docker network and has no route to
+A failed check does not stop the others.
 the internet, so the app's latency probes cannot reach anything real. The
 harness answers them itself from a fixed delay table, with a deterministic
 fraction failed outright, so the rows render a realistic spread of one-, two-
 and three-digit latencies plus some unreachable rows. That spread is what the
 layout has to survive; a `---` placeholder in every row would not exercise it.
-## What this cannot verify
+- `app-rendered`: at least 10 WAN host rows exist, and at least 5 rows show a
  number as their latency. Without this, the other checks could pass against a
  blank page.
 - `no-horizontal-overflow`: the document is no wider than the window. On a
  failure, the widest content is named.
 - `nothing-past-viewport-edge`: no visible element extends past the window's
  edge.
 - `no-clipped-text`: no element hides its text behind `overflow: hidden` or
  `overflow: clip`. Text cut with an ellipsis is allowed: that cut is a design
  choice, not a defect. Tailwind's `truncate` cuts host names and URLs that way.
 - `tap-targets-44px`, on touch widths: each measured control is at least 44 by
  44 CSS pixels. The controls are `#pause-btn`, `#interval-select`,
  `#debug-toggle` and the `.pin-btn` in each WAN host row. The check also
  demands that each selector matches enough visible elements: one of each single
  control, and one pin button per WAN host row. A renamed class would otherwise
  take its controls out of the measured set, and the check would pass on
  nothing.
 - `host-rows-stacked` or `host-rows-side-by-side`: each host row shows the
  layout expected at that width. In the narrow layout, the row's
  `flex-direction` is `column`, the graph sits below the host's details, and
  each takes at least 90% of the row's width. In the wide layout, the direction
  is `row` and the graph sits to the right of the details. A row that only
  shrank its fixed 420-pixel column fails.
 - `probing-still-runs`: the page sent at least one check to a target at this
  width. The narrow layout must not skip the checks.
 - `gateway-detection-still-runs`: the `Local Gateway` row is present at this
  width, so the gateway was looked for and found. The narrow layout must not
  skip that search.
-Real limits, so nobody re-parks this issue as needing hardware:
+### The tap-target size
- **Non-Chromium engines.** This is Chrome. iOS Safari is WebKit and cannot be
+44 by 44 CSS pixels is the figure in Apple's Human Interface Guidelines and in
-  emulated by it; Safari-specific bugs (viewport units under a collapsing URL
+WCAG 2.2 success criterion 2.5.5, "Target Size (Enhanced)". WCAG 2.2 criterion
-  bar, `-webkit-fill-available`, form control metrics) will not show up here.
+2.5.8 sets a lower minimum of 24 by 24 pixels, with an exception that depends on
- **Real touch input.** `hasTouch` emulation changes what the page is told, not
+the space around a control. The pin buttons sit against the host name they
-  how a finger behaves. Gesture handling, scroll momentum, double-tap zoom and
+belong to, so the test keeps 44.
  hover-state fallbacks on touch are out of scope.
 - **Physical pixel density and rendering.** `deviceScaleFactor` is set, but
  subpixel antialiasing, OLED colour rendering and actual legibility at a given
  physical size are not measurable here.
 - **Fonts.** The container has DejaVu, not the platform's own UI monospace. Text
  metrics are therefore close to, but not identical to, a real device — a layout
  that fits here by a few pixels might not there.
 - **On-device performance.** Canvas sparkline redraw cost, battery, and
  behaviour on a slow radio are not measured.
 - **Browser chrome.** The address bar, safe-area insets and notch cutouts are
  not simulated.
-Everything else this issue was actually about — does the layout reflow, does
+## The browser's network
-anything overflow, is content clipped, are the controls big enough — is a
+
-function of viewport width and CSS, and is covered above.
+The browser container runs on an internal Docker network with no route to the
 internet, so the page's checks reach no real host. The test answers them itself
 from a fixed table of delays: 2, 45, 123, 456 and 780 milliseconds. Which delay
 a target gets depends on its URL, and about one target in seven fails outright.
 So the rows show one-, two- and three-digit latencies and some unreachable rows,
 and the layout is tested against that spread. The request to
 `http://192.168.1.1` is answered after 5 milliseconds, so the `Local Gateway`
 row appears.
 At each width, the test sets the interval to 1 second and waits until at least 5
 rows show a latency before it measures. The page discards its first round, so
 this reaches a filled page without waiting out two rounds at 3 seconds.
 ## What the test cannot check
 - Other browser engines. The test runs Chrome. Safari uses WebKit, and bugs that
  only WebKit has do not show up here.
 - Real touch input. Touch emulation changes what the page is told, not how a
  finger behaves. Gestures, scroll momentum, double-tap zoom and hover states on
  touch are not tested.
 - Physical pixels. The device pixel ratio is set, but antialiasing, colour
  rendering and legibility at a given physical size are not measured.
 - Fonts. The container has DejaVu, not a phone's own monospace font. Text is
  about as wide as on a real device, but not exactly. A layout that fits here by
  a few pixels might not fit there.
 - Performance. The cost of redrawing the graphs, battery use and behaviour on a
  slow connection are not measured.
 - The browser's own frame. The address bar, safe-area insets and notch cutouts
  are not simulated.
 ## The files
 - `viewports.js` derives the widths from the sources.
 - `facts.js` is run inside the page and measures the layout. It only measures;
  it decides nothing.
 - `checks.js` turns the measurements into the pass or fail of each check, with
  the numbers that decided it.
 - `harness.js` connects to the browser, runs each width, writes the screenshots
  and `results.json`, and prints the results. `script/frontend-viewport-test`
  starts it; every input it needs arrives in the environment.
 ## Relation to the unit tests
-Complementary layers, not two stacks. The unit tests in `test/unit/`, which
+The unit tests in `test/unit/` call the functions that `web/src/main.js`
-`make test` runs with Node's built-in test runner, exercise the functions
+exports, with no browser. `make test` runs them with Node's built-in test
-`web/src/main.js` exports in-process with no browser. This harness exercises
+runner. This test runs the built page in a real browser engine and is the only
-rendered layout in a real engine and is the only thing here that can see a media
+test here that can see a media query. Neither replaces the other. Checks on
-query. Neither replaces the other; assertions about computed styles and element
+computed styles and element geometry belong here; checks on functions belong in
-geometry belong here, assertions about functions belong in `test/unit/`.
+`test/unit/`.