Go tests run with -race and -cover under Go's own timeout (closes #88)

backend/script/test runs go test -timeout 30s -race -cover and, if
that fails, runs it again with -v and fails. The root script/test drops
its one 30-second timeout around both halves: from a cold Go build
cache, compiling the tests with -race used it all up. Each half keeps
its own limit. The race detector needs a C compiler: the Dockerfile
builder stage gains gcc and musl-dev, and script/bootstrap installs gcc,
with the C library headers on apt and apk, when gcc is missing; make
build still sets CGO_ENABLED=0. New tests: the health check's answer, a
valid report's answer, a report file's exact lines, and the flush at the
10 MiB threshold. The handlers TestImport stub is gone.

Model: opus-5-5

Dockerfile

@@ -68,8 +68,9 @@ RUN yarn install --frozen-lockfile
 RUN apk add --no-cache git make
 COPY . .
 # make frontend-check is the frontend half of make check (test + lint +
-# fmt-check); its test step is the production yarn build, so this both
-# produces dist/ and gates the image on lint/fmt-check/test regressions.
+# fmt-check); its test step runs the unit tests, then the production
+# yarn build, so this both produces dist/ and gates the image on
+# lint/fmt-check/test regressions.
 # This node stage has neither Go nor Docker; the lint and builder stages
 # above gate the backend half.
 RUN make frontend-check

README.md

@@ -39,9 +39,11 @@ halves, so the root `make check` fails if either one is broken. We provide:
 - `script/bootstrap` — install all dependencies (the pinned node via nvm unless
   one new enough for the frontend's dependencies is installed, yarn via
   corepack, `yarn install --frozen-lockfile`, the pinned Go unless one at least
-  as new as `backend/go.mod` asks for is installed, and the Go modules), linking
-  what it installs itself into `~/.local/bin`, which has to be on `PATH`. It
-  installs no Go linter and not Docker: `make lint` runs the linter in Docker
+  as new as `backend/go.mod` asks for is installed, the Go modules, and gcc with
+  the C library headers unless gcc is installed, for the race detector in
+  `make test`), linking what it installs itself into `~/.local/bin`, which has
+  to be on `PATH`. It installs no Go linter and not Docker: `make lint` runs the
+  linter in Docker
 - `script/setup` — make a fresh clone ready for development: bootstrap plus the
   git pre-commit hook
 - `script/projectname` — print the project name (used for the Docker image tag)
@@ -52,8 +54,8 @@ halves, so the root `make check` fails if either one is broken. We provide:
 - `script/fmt` — format all files (writes): prettier, then gofmt over `backend/`
 - `script/fmt-check` — check formatting (read-only): prettier, then gofmt
 - `script/check` — run test, lint, and fmt-check
-- `script/frontend-test` — run the production build as the frontend's test (no
-  unit tests yet)
+- `script/frontend-test` — run the unit tests in `test/unit/` with Node's
+  built-in test runner, then the production build
 - `script/frontend-lint` — run prettier in check mode
 - `script/frontend-fmt` — format everything prettier understands (writes)
 - `script/frontend-fmt-check` — check prettier formatting (read-only)
@@ -136,8 +138,14 @@ Local hosts are tracked separately from WAN stats.
 ### Latency measurement
 
 HEAD requests with `mode: 'no-cors'` and `cache: 'no-store'`, timed with
-`performance.now()`. 1-second timeout; anything over 1000ms is clamped to
-unreachable. IPv4 only.
+`performance.now()`. Each check times out after 80% of the refresh interval (24
+seconds at 30 seconds) and is then recorded as a timeout, so a round's checks
+have all finished before the next round is due. When no WAN host answers, a
+recovery probe checks 4 random WAN hosts every half second, giving up the checks
+it started half a second before. As soon as one answers, a new round starts at
+once, as it does after an interval change. A round started early gives up the
+last round's checks if they are still waiting, and that round records nothing,
+so rounds never overlap. IPv4 only.
 
 ### Color coding
 

TODO.md

@@ -28,11 +28,20 @@ latest run passes.
   that fails, runs it again with `-v` and fails. Go's `-timeout` bounds the
   tests, not their compile; the root `script/test` no longer puts one 30-second
   timeout around both halves, which a cold Go build cache could use up on
-  compiling alone. The builder stage of `Dockerfile` has gcc and musl-dev for
-  the race detector; the binary is still built with `CGO_ENABLED=0`. New tests
-  cover the health check's answer, a valid report's answer, a report file's
-  exact contents, and the flush when the buffer reaches 10 MiB; the handlers'
-  `TestImport` stub is gone
+  compiling alone. The race detector needs a C compiler: the builder stage of
+  `Dockerfile` has gcc and musl-dev, and `script/bootstrap` installs gcc, with
+  the C library headers on apt and apk, when gcc is missing; the binary is still
+  built with `CGO_ENABLED=0`. New tests cover the health check's answer, a valid
+  report's answer, a report file's exact contents, and the flush when the buffer
+  reaches 10 MiB; the handlers' `TestImport` stub is gone
+- 2026-10-03: each target check times out after 80% of the refresh interval
+  (issue #78), 24 seconds at 30 seconds, where it was capped at 3 seconds. A
+  round started early, after an interval change or when the recovery probe finds
+  a target answering, gives up the last round's checks if they are still
+  waiting, so rounds never overlap; the recovery probe gives up its own checks
+  after half a second. The frontend has its first unit tests, run by
+  `script/frontend-test` with Node's built-in test runner; for them,
+  `index.html` now links `src/styles.css`, which `src/main.js` used to import
 - 2026-09-29: the container sets up its own data directory (issue #75):
   `bin/entrypoint.sh`, still as root, creates `DATA_DIR` if missing and gives it
   and `/data` to the `netwatch` user with mode 750 before starting the backend

index.html

@@ -9,6 +9,9 @@
             type="image/svg+xml"
             href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='.9em' font-size='90'>📡</text></svg>"
         />
+        <!-- Linked here, not imported by src/main.js, so the unit tests can
+             import that module in Node, which cannot import CSS. -->
+        <link rel="stylesheet" href="/src/styles.css" />
     </head>
     <body class="bg-gray-900 text-white min-h-screen">
         <div id="app"></div>

script/bootstrap

@@ -64,7 +64,8 @@ detect_pkgmgr() {
     fi
 }
 
-# pkg_install <nix-attr> <apt-pkg> <brew-formula> <apk-pkg>
+# pkg_install <nix-attr> <apt-pkgs> <brew-formula> <apk-pkgs>: the apt
+# and apk arguments may each list several packages, separated by spaces.
 pkg_install() {
     detect_pkgmgr
     case "$PKGMGR" in
@@ -74,10 +75,10 @@ pkg_install() {
                 $SUDO env DEBIAN_FRONTEND=noninteractive apt-get update
                 APT_UPDATED=1
             fi
-            $SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y "$2"
+            $SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y $2
             ;;
         brew) brew install "$3" ;;
-        apk) apk add --no-cache "$4" ;;
+        apk) apk add --no-cache $4 ;;
     esac
 }
 
@@ -253,6 +254,12 @@ main() {
 
     if missing make; then pkg_install gnumake make make make; fi
     if missing git; then pkg_install git git git git; fi
+    # The race detector in make test needs cgo, which Go turns on only
+    # when it finds its C compiler, gcc on Linux. apt and apk ship the C
+    # library headers apart from gcc.
+    if missing gcc; then
+        pkg_install gcc "gcc libc6-dev" gcc "gcc musl-dev"
+    fi
 
     ensure_node
     ensure_yarn

script/frontend-test

@@ -1,13 +1,14 @@
 #!/bin/sh
-# script/frontend-test: run the frontend test suite. The frontend has no
-# unit tests; the production build serves as the test (fails on broken
-# code).
+# script/frontend-test: run the frontend test suite: the unit tests in
+# test/unit/ with Node's built-in test runner, then the production
+# build, which fails on broken code.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
+    timeout 30 node --test test/unit/*.test.js
     timeout 30 yarn build
 }
 

src/main.js

@@ -1,14 +1,14 @@
-import "./styles.css";
-
 // --- Configuration -----------------------------------------------------------
 
-// Timing, axis labels, and display constants. Latency above maxLatency is
-// clamped to "unreachable". The sparkline Y-axis is capped at
+// Timing, axis labels, and display constants. A target check times out
+// after requestTimeout, 80% of updateInterval, so a round's checks have
+// all finished before the next round is due; latency above maxLatency is
+// recorded as a timeout. The sparkline Y-axis is capped at
 // graphMaxLatency — values above it pin to the top of the chart but still
 // display their real value in the latency figure. The history buffer holds
 // maxHistoryPoints samples (historyDuration / updateInterval).
 // reportInterval is how often collected samples are POSTed to the backend.
-const CONFIG = {
+export const CONFIG = {
     updateInterval: 3000,
     maxHistoryPoints: 100,
     reportInterval: 60000,
@@ -16,7 +16,7 @@ const CONFIG = {
         return (this.maxHistoryPoints * this.updateInterval) / 1000;
     },
     get requestTimeout() {
-        return Math.min(this.updateInterval - 100, 3000);
+        return this.updateInterval * 0.8;
     },
     get maxLatency() {
         return this.requestTimeout;
@@ -503,12 +503,16 @@ class Reporter {
 
 // --- Latency Measurement -----------------------------------------------------
 
-async function measureLatency(url) {
+// Checks one target. The check times out after CONFIG.requestTimeout; the
+// caller can give it up sooner through the optional signal, which also ends
+// it as a timeout.
+export async function measureLatency(url, signal) {
     const controller = new AbortController();
     const timeoutId = setTimeout(
         () => controller.abort(),
         CONFIG.requestTimeout,
     );
+    signal?.addEventListener("abort", () => controller.abort());
 
     const targetUrl = new URL(url);
     targetUrl.searchParams.set("_cb", Date.now().toString());
@@ -1101,7 +1105,7 @@ function sortAndRebuildWAN(state) {
 
 // --- Main Loop ---------------------------------------------------------------
 
-async function tick(state, onOffline) {
+async function tick(state, signal, onOffline) {
     const ts = Date.now();
 
     if (state.paused) {
@@ -1123,11 +1127,12 @@ async function tick(state, onOffline) {
     log.debug(`Tick #${state.tickCount + 1} started`);
 
     const results = await Promise.all(
-        state.allHosts.map((h) => measureLatency(h.url)),
+        state.allHosts.map((h) => measureLatency(h.url, signal)),
     );
 
-    // User may have paused while awaiting results — discard them
-    if (state.paused) return;
+    // User may have paused, or the next round may have given up this
+    // one's checks, while awaiting results — discard them
+    if (state.paused || signal.aborted) return;
 
     state.tickCount++;
 
@@ -1168,9 +1173,10 @@ async function tick(state, onOffline) {
 
 // --- Recovery Probe ----------------------------------------------------------
 
-// When offline, rapidly poll 4 random WAN hosts every 500ms. As soon as any
-// responds, stop probing and fire a normal tick to refresh all hosts.
-function startRecoveryProbe(state, triggerTick) {
+// When offline, check 4 random WAN hosts every 500ms, giving up the checks
+// started 500ms before, so at most 4 are ever waiting. As soon as one
+// answers, stop probing and start a new round at once.
+function startRecoveryProbe(state, startRounds) {
     if (state._recoveryProbeId) return; // already running
     const candidates = [...state.wan];
     for (let i = candidates.length - 1; i > 0; i--) {
@@ -1181,15 +1187,18 @@ function startRecoveryProbe(state, triggerTick) {
     log.notice(
         `Recovery probe started (${canaries.map((h) => h.name).join(", ")})`,
     );
-    state._recoveryProbeId = setInterval(async () => {
+    state._recoveryProbeId = setInterval(() => {
         if (state.paused) return;
-        const results = await Promise.all(
-            canaries.map((h) => measureLatency(h.url)),
-        );
-        if (results.some((r) => r.error === null)) {
-            log.notice("Recovery probe: connectivity detected");
-            stopRecoveryProbe(state);
-            triggerTick();
+        state._recoveryProbeChecks?.abort();
+        const checks = new AbortController();
+        state._recoveryProbeChecks = checks;
+        for (const host of canaries) {
+            measureLatency(host.url, checks.signal).then((r) => {
+                if (r.error !== null || checks.signal.aborted) return;
+                log.notice("Recovery probe: connectivity detected");
+                stopRecoveryProbe(state);
+                startRounds();
+            });
         }
     }, 500);
 }
@@ -1198,6 +1207,7 @@ function stopRecoveryProbe(state) {
     if (state._recoveryProbeId) {
         clearInterval(state._recoveryProbeId);
         state._recoveryProbeId = null;
+        state._recoveryProbeChecks?.abort();
     }
 }
 
@@ -1374,18 +1384,34 @@ async function init() {
     updateClocks();
     setInterval(updateClocks, 1000);
 
+    // Rounds never overlap: a round first gives up the last round's checks
+    // if they are still waiting, and the last round then records nothing.
+    // At a steady interval they never are, as they time out at 80% of it;
+    // they can be when a round starts early, after an interval change or
+    // when the recovery probe finds a target answering.
+    let roundChecks = new AbortController();
     function doTick() {
-        tick(state, () => startRecoveryProbe(state, doTick));
+        roundChecks.abort();
+        roundChecks = new AbortController();
+        tick(state, roundChecks.signal, () =>
+            startRecoveryProbe(state, startRounds),
+        );
     }
 
-    doTick();
-    let tickIntervalId = setInterval(doTick, CONFIG.updateInterval);
+    // Starts a round now and then one every CONFIG.updateInterval.
+    let tickIntervalId;
+    function startRounds() {
+        clearInterval(tickIntervalId);
+        doTick();
+        tickIntervalId = setInterval(doTick, CONFIG.updateInterval);
+    }
+
+    startRounds();
 
     document
         .getElementById("interval-select")
         .addEventListener("change", (e) => {
             const newInterval = parseInt(e.target.value, 10);
-            clearInterval(tickIntervalId);
             CONFIG.updateInterval = newInterval;
             log.notice(
                 `Interval changed to ${humanDuration(newInterval / 1000)}, history reset`,
@@ -1434,8 +1460,7 @@ async function init() {
 
             // Start immediately with new interval
             stopRecoveryProbe(state);
-            doTick();
-            tickIntervalId = setInterval(doTick, CONFIG.updateInterval);
+            startRounds();
         });
 
     window.addEventListener("resize", () => handleResize(state));
@@ -1444,7 +1469,7 @@ async function init() {
 
 // Bootstrap only when loaded as the page: a real DOM containing the #app
 // mount point this module renders into. Importing the module in a unit test
-// (which has no #app) runs nothing, so buildReport can be tested in isolation.
+// (which has no #app) runs nothing, so its exports can be tested in isolation.
 if (typeof document !== "undefined" && document.getElementById("app")) {
     if (document.readyState === "loading") {
         document.addEventListener("DOMContentLoaded", init);

test/unit/main.test.js

@@ -0,0 +1,66 @@
+// Unit tests for src/main.js, run by script/frontend-test with Node's
+// built-in test runner. Importing the module does not start the page.
+
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { CONFIG, measureLatency } from "../../src/main.js";
+
+// measureLatency writes timeouts to the debug log, which looks for its
+// panel in the page. There is no page here.
+globalThis.document = { getElementById: () => null };
+
+// Mocks the clock for test t, so that a check lasting seconds takes no real
+// time, and replaces fetch with a target that answers after answerAfter
+// milliseconds of that clock, or never when answerAfter is Infinity. Both
+// are restored when the test ends.
+function mockTarget(t, answerAfter) {
+    t.mock.timers.enable({ apis: ["setTimeout", "Date"] });
+    t.mock.method(performance, "now", () => Date.now());
+    t.mock.method(
+        globalThis,
+        "fetch",
+        (url, { signal }) =>
+            new Promise((resolve, reject) => {
+                if (answerAfter !== Infinity) setTimeout(resolve, answerAfter);
+                signal.addEventListener("abort", () => reject(signal.reason));
+            }),
+    );
+}
+
+// The result of check if it has ended, otherwise "still waiting".
+function settled(check) {
+    return Promise.race([
+        check,
+        new Promise((resolve) => setImmediate(resolve, "still waiting")),
+    ]);
+}
+
+for (const interval of [10000, 30000]) {
+    const timeout = interval * 0.8;
+    // Over 3 seconds, which the timeout used to be capped at.
+    const slowAnswer = timeout - 1000;
+
+    test(`at a ${interval}ms interval, an answer after ${slowAnswer}ms is recorded with its real time`, async (t) => {
+        CONFIG.updateInterval = interval;
+        mockTarget(t, slowAnswer);
+        const check = measureLatency("https://target.test");
+        t.mock.timers.tick(slowAnswer);
+        assert.deepEqual(await settled(check), {
+            latency: slowAnswer,
+            error: null,
+        });
+    });
+
+    test(`at a ${interval}ms interval, a target that never answers is recorded as a timeout after ${timeout}ms`, async (t) => {
+        CONFIG.updateInterval = interval;
+        mockTarget(t, Infinity);
+        const check = measureLatency("https://target.test");
+        t.mock.timers.tick(timeout - 1);
+        assert.equal(await settled(check), "still waiting");
+        t.mock.timers.tick(1);
+        assert.deepEqual(await settled(check), {
+            latency: null,
+            error: "timeout",
+        });
+    });
+}