diff --git a/tests/js/countdown-test.js b/tests/js/countdown-test.js
new file mode 100644
index 0000000..de53e85
--- /dev/null
+++ b/tests/js/countdown-test.js
@@ -0,0 +1,190 @@
+/**
+ * Tests unitaires pour js/countdown.js (classe CountdownTimer).
+ *
+ * Le script est chargé dans un contexte vm avec un DOM simulé :
+ * la date courante est figée (FakeDate) et setInterval est factice,
+ * ce qui rend les calculs de temps restant déterministes.
+ */
+'use strict';
+
+const { describe, test } = require('node:test');
+const assert = require('node:assert');
+const fs = require('node:fs');
+const path = require('node:path');
+const vm = require('node:vm');
+
+const COUNTDOWN_PATH = path.join(__dirname, '..', '..', 'js', 'countdown.js');
+const COUNTDOWN_SOURCE = fs.readFileSync(COUNTDOWN_PATH, 'utf8');
+
+// Date courante figée pour tous les tests
+const FIXED_NOW = new Date('2030-01-01T00:00:00Z').getTime();
+
+function makeElements() {
+    return {
+        'countdown-days': { textContent: '' },
+        'countdown-hours': { textContent: '' },
+        'countdown-minutes': { textContent: '' },
+        'countdown-seconds': { textContent: '' }
+    };
+}
+
+/**
+ * Charge countdown.js dans un contexte vm isolé et retourne la classe.
+ *
+ * @param {object|null} options.elements  Éléments DOM simulés (null = absents)
+ * @param {number}      options.now       Timestamp courant simulé
+ */
+function loadCountdown({ elements = null, now = FIXED_NOW } = {}) {
+    class FakeDate extends Date {
+        constructor(...args) {
+            if (args.length === 0) {
+                super(now);
+            } else {
+                super(...args);
+            }
+        }
+
+        static now() {
+            return now;
+        }
+    }
+
+    const windowMock = {
+        addEventListener() {},
+        location: { href: '' }
+    };
+
+    // Timers factices : le timer ne tourne jamais tout seul,
+    // on enregistre simplement les appels pour vérification.
+    const timers = { intervals: [], cleared: [] };
+    let nextIntervalId = 1;
+
+    const sandbox = {
+        document: {
+            getElementById: (id) => (elements ? elements[id] || null : null),
+            querySelectorAll: () => [],
+            addEventListener() {}
+        },
+        window: windowMock,
+        Date: FakeDate,
+        setInterval: (fn, delay) => {
+            const id = nextIntervalId++;
+            timers.intervals.push({ id, fn, delay });
+            return id;
+        },
+        clearInterval: (id) => {
+            timers.cleared.push(id);
+        },
+        setTimeout: () => 0,
+        console
+    };
+
+    vm.createContext(sandbox);
+    const CountdownTimer = vm.runInContext(COUNTDOWN_SOURCE + '\nCountdownTimer;', sandbox);
+
+    return { CountdownTimer, window: windowMock, timers };
+}
+
+describe('CountdownTimer', () => {
+    test('formatNumber complète les nombres sur deux chiffres', () => {
+        const { CountdownTimer } = loadCountdown();
+
+        assert.strictEqual(CountdownTimer.prototype.formatNumber(0), '00');
+        assert.strictEqual(CountdownTimer.prototype.formatNumber(5), '05');
+        assert.strictEqual(CountdownTimer.prototype.formatNumber(42), '42');
+        assert.strictEqual(CountdownTimer.prototype.formatNumber(123), '123');
+    });
+
+    test('calcule correctement le temps restant (jours/heures/minutes/secondes)', () => {
+        const distance =
+            2 * 24 * 60 * 60 * 1000 + // 2 jours
+            3 * 60 * 60 * 1000 +      // 3 heures
+            4 * 60 * 1000 +           // 4 minutes
+            5 * 1000;                 // 5 secondes
+
+        const elements = makeElements();
+        const { CountdownTimer } = loadCountdown({ elements });
+        const timer = new CountdownTimer(FIXED_NOW + distance);
+
+        try {
+            assert.strictEqual(elements['countdown-days'].textContent, '02');
+            assert.strictEqual(elements['countdown-hours'].textContent, '03');
+            assert.strictEqual(elements['countdown-minutes'].textContent, '04');
+            assert.strictEqual(elements['countdown-seconds'].textContent, '05');
+        } finally {
+            timer.stop();
+        }
+    });
+
+    test('reporte les heures au-delà de 24h dans les jours', () => {
+        const distance = 36 * 60 * 60 * 1000; // 36 heures = 1 jour + 12 heures
+
+        const elements = makeElements();
+        const { CountdownTimer } = loadCountdown({ elements });
+        const timer = new CountdownTimer(FIXED_NOW + distance);
+
+        try {
+            assert.strictEqual(elements['countdown-days'].textContent, '01');
+            assert.strictEqual(elements['countdown-hours'].textContent, '12');
+            assert.strictEqual(elements['countdown-minutes'].textContent, '00');
+            assert.strictEqual(elements['countdown-seconds'].textContent, '00');
+        } finally {
+            timer.stop();
+        }
+    });
+
+    test('une date passée arrête le compte à rebours et redirige vers /', () => {
+        const elements = makeElements();
+        const { CountdownTimer, window } = loadCountdown({ elements });
+        const timer = new CountdownTimer(FIXED_NOW - 1000);
+
+        try {
+            // onComplete() redirige vers la page principale
+            assert.strictEqual(window.location.href, '/');
+
+            // Les éléments ne sont pas mis à jour quand le compte est terminé
+            assert.strictEqual(elements['countdown-days'].textContent, '');
+            assert.strictEqual(elements['countdown-hours'].textContent, '');
+            assert.strictEqual(elements['countdown-minutes'].textContent, '');
+            assert.strictEqual(elements['countdown-seconds'].textContent, '');
+        } finally {
+            timer.stop();
+        }
+    });
+
+    test('une distance nulle affiche zéro partout sans rediriger', () => {
+        const elements = makeElements();
+        const { CountdownTimer, window } = loadCountdown({ elements });
+        const timer = new CountdownTimer(FIXED_NOW);
+
+        try {
+            assert.strictEqual(elements['countdown-days'].textContent, '00');
+            assert.strictEqual(elements['countdown-hours'].textContent, '00');
+            assert.strictEqual(elements['countdown-minutes'].textContent, '00');
+            assert.strictEqual(elements['countdown-seconds'].textContent, '00');
+            assert.strictEqual(window.location.href, '');
+        } finally {
+            timer.stop();
+        }
+    });
+
+    test('fonctionne sans éléments DOM présents', () => {
+        const { CountdownTimer } = loadCountdown({ elements: null });
+        const timer = new CountdownTimer(FIXED_NOW + 60 * 1000);
+
+        // Aucune erreur attendue malgré l'absence des éléments
+        timer.stop();
+    });
+
+    test('démarre un intervalle d\'une seconde et stop() le nettoie', () => {
+        const { CountdownTimer, timers } = loadCountdown();
+        const timer = new CountdownTimer(FIXED_NOW + 60 * 1000);
+
+        assert.strictEqual(timers.intervals.length, 1);
+        assert.strictEqual(timers.intervals[0].delay, 1000);
+        assert.strictEqual(timers.cleared.length, 0);
+
+        timer.stop();
+        assert.deepStrictEqual(timers.cleared, [timer.interval]);
+    });
+});
diff --git a/tests/js/pleroma-adapter-test.js b/tests/js/pleroma-adapter-test.js
new file mode 100644
index 0000000..cc75287
--- /dev/null
+++ b/tests/js/pleroma-adapter-test.js
@@ -0,0 +1,311 @@
+/**
+ * Unit tests for js/pleroma-adapter.js.
+ *
+ * The adapter is an IIFE that wraps window.fetch. It is loaded in a vm
+ * context with a mocked window object, so tests can call the wrapped
+ * fetch and inspect how Pleroma API responses are mapped to the
+ * Mastodon format expected by mastodon-timeline.umd.js.
+ */
+'use strict';
+
+const { describe, test } = require('node:test');
+const assert = require('node:assert');
+const fs = require('node:fs');
+const path = require('node:path');
+const vm = require('node:vm');
+
+const ADAPTER_PATH = path.join(__dirname, '..', '..', 'js', 'pleroma-adapter.js');
+const ADAPTER_SOURCE = fs.readFileSync(ADAPTER_PATH, 'utf8');
+
+const TIMELINE_URL = 'https://pleroma.example/api/v1/timelines/public';
+const ACCOUNT_STATUSES_URL = 'https://pleroma.example/api/v1/accounts/42/statuses';
+
+/**
+ * Loads the adapter in an isolated vm context.
+ *
+ * @param {Function} handler  Fake backend: receives the URL, returns a Response
+ * @returns {{fetch: Function, warnings: string[]}} The wrapped fetch and logged warnings
+ */
+function loadAdapter(handler) {
+    const warnings = [];
+    const windowMock = {
+        fetch: async (url) => handler(url)
+    };
+
+    const sandbox = {
+        window: windowMock,
+        Response,
+        console: {
+            log() {},
+            warn: (...args) => warnings.push(args.join(' ')),
+            error() {}
+        }
+    };
+
+    vm.createContext(sandbox);
+    vm.runInContext(ADAPTER_SOURCE, sandbox);
+
+    return { fetch: windowMock.fetch, warnings };
+}
+
+function jsonResponse(data, init = {}) {
+    return new Response(JSON.stringify(data), {
+        status: 200,
+        headers: { 'Content-Type': 'application/json' },
+        ...init
+    });
+}
+
+describe('Pleroma adapter', () => {
+    test('adds default meta to timeline attachments missing meta', async () => {
+        const posts = [
+            {
+                id: '1',
+                content: 'hello',
+                media_attachments: [
+                    { id: 'a1', type: 'image', url: 'https://pleroma.example/img.png' }
+                ]
+            },
+            { id: '2', content: 'no media' }
+        ];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        assert.strictEqual(res.status, 200);
+        assert.strictEqual(data.length, 2);
+
+        const attachment = data[0].media_attachments[0];
+        assert.deepStrictEqual(attachment.meta.original, {
+            width: 1280,
+            height: 720,
+            aspect: 1280 / 720
+        });
+        assert.deepStrictEqual(attachment.meta.small, {
+            width: 640,
+            height: 360,
+            aspect: 1280 / 720
+        });
+        // Other fields are preserved
+        assert.strictEqual(attachment.url, 'https://pleroma.example/img.png');
+        assert.strictEqual(data[0].content, 'hello');
+        assert.strictEqual(data[1].content, 'no media');
+        assert.strictEqual(data[1].media_attachments, undefined);
+    });
+
+    test('uses 1920x1080 for video attachments (pleroma mime_type)', async () => {
+        const posts = [
+            {
+                id: '9',
+                media_attachments: [
+                    { id: 'v1', pleroma: { mime_type: 'video/mp4' } }
+                ]
+            }
+        ];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(ACCOUNT_STATUSES_URL);
+        const data = await res.json();
+
+        const meta = data[0].media_attachments[0].meta;
+        assert.deepStrictEqual(meta.original, {
+            width: 1920,
+            height: 1080,
+            aspect: 1920 / 1080
+        });
+        assert.deepStrictEqual(meta.small, {
+            width: 960,
+            height: 540,
+            aspect: 1920 / 1080
+        });
+    });
+
+    test('uses 1200x800 for image attachments (pleroma mime_type)', async () => {
+        const post = {
+            id: '10',
+            media_attachments: [
+                { id: 'i1', pleroma: { mime_type: 'image/jpeg' } }
+            ]
+        };
+        const { fetch } = loadAdapter(() => jsonResponse(post));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        const meta = data.media_attachments[0].meta;
+        assert.deepStrictEqual(meta.original, {
+            width: 1200,
+            height: 800,
+            aspect: 1200 / 800
+        });
+        assert.deepStrictEqual(meta.small, {
+            width: 600,
+            height: 400,
+            aspect: 1200 / 800
+        });
+    });
+
+    test('adapts a single (non-array) post object', async () => {
+        const post = {
+            id: 'single',
+            media_attachments: [{ id: 's1' }]
+        };
+        const { fetch } = loadAdapter(() => jsonResponse(post));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        assert.strictEqual(Array.isArray(data), false);
+        assert.strictEqual(data.id, 'single');
+        assert.deepStrictEqual(data.media_attachments[0].meta.original, {
+            width: 1280,
+            height: 720,
+            aspect: 1280 / 720
+        });
+    });
+
+    test('leaves attachments with complete meta untouched', async () => {
+        const completeMeta = {
+            original: { width: 640, height: 480, aspect: 640 / 480 },
+            small: { width: 320, height: 240, aspect: 640 / 480 }
+        };
+        const posts = [
+            { id: 'm1', media_attachments: [{ id: 'ok', meta: completeMeta }] }
+        ];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        assert.deepStrictEqual(data[0].media_attachments[0].meta, completeMeta);
+    });
+
+    test('keeps existing partial meta.original and fills meta.small', async () => {
+        const posts = [
+            {
+                id: 'p1',
+                media_attachments: [
+                    {
+                        id: 'partial',
+                        meta: { original: { width: 640, height: 480, aspect: 640 / 480 } }
+                    }
+                ]
+            }
+        ];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        const meta = data[0].media_attachments[0].meta;
+        assert.deepStrictEqual(meta.original, { width: 640, height: 480, aspect: 640 / 480 });
+        // meta.small is created from the default dimensions
+        assert.deepStrictEqual(meta.small, {
+            width: 640,
+            height: 360,
+            aspect: 1280 / 720
+        });
+    });
+
+    test('adapts media attachments inside reblogs recursively', async () => {
+        const posts = [
+            {
+                id: 'r1',
+                reblog: {
+                    id: 'r2',
+                    media_attachments: [
+                        { id: 'rb', pleroma: { mime_type: 'image/png' } }
+                    ]
+                }
+            }
+        ];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        const meta = data[0].reblog.media_attachments[0].meta;
+        assert.deepStrictEqual(meta.original, {
+            width: 1200,
+            height: 800,
+            aspect: 1200 / 800
+        });
+    });
+
+    test('does not mutate the original payload objects', async () => {
+        const attachment = { id: 'orig' };
+        const posts = [{ id: 'n1', media_attachments: [attachment] }];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(TIMELINE_URL);
+        await res.json();
+
+        assert.strictEqual(attachment.meta, undefined);
+        assert.deepStrictEqual(posts[0].media_attachments, [attachment]);
+    });
+
+    test('passes non-object array entries through unchanged', async () => {
+        const posts = [null, 'not-a-post', { id: 'real', media_attachments: [{ id: 'x' }] }];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        const res = await fetch(TIMELINE_URL);
+        const data = await res.json();
+
+        assert.strictEqual(data[0], null);
+        assert.strictEqual(data[1], 'not-a-post');
+        assert.ok(data[2].media_attachments[0].meta);
+    });
+
+    test('intercepts account statuses URLs only when they contain /statuses', async () => {
+        const posts = [{ id: 'a', media_attachments: [{ id: 'x' }] }];
+        const { fetch } = loadAdapter(() => jsonResponse(posts));
+
+        // /api/v1/accounts/42/statuses is adapted
+        const resStatuses = await fetch(ACCOUNT_STATUSES_URL);
+        const dataStatuses = await resStatuses.json();
+        assert.ok(dataStatuses[0].media_attachments[0].meta);
+
+        // /api/v1/accounts/42 (no /statuses) is left as-is
+        const resAccount = await fetch('https://pleroma.example/api/v1/accounts/42');
+        const dataAccount = await resAccount.json();
+        assert.strictEqual(dataAccount[0].media_attachments[0].meta, undefined);
+    });
+
+    test('returns non-API responses untouched (same Response object)', async () => {
+        let original;
+        const { fetch } = loadAdapter(() => {
+            original = jsonResponse({ ok: true });
+            return original;
+        });
+
+        const res = await fetch('https://example.com/about');
+
+        assert.strictEqual(res, original);
+        assert.deepStrictEqual(await res.json(), { ok: true });
+    });
+
+    test('falls back to the original response when JSON parsing fails', async () => {
+        let original;
+        const { fetch, warnings } = loadAdapter(() => {
+            original = new Response('not-json', { status: 200 });
+            return original;
+        });
+
+        const res = await fetch(TIMELINE_URL);
+
+        assert.strictEqual(res, original);
+        assert.strictEqual(await res.text(), 'not-json');
+        assert.strictEqual(warnings.length, 1);
+    });
+
+    test('preserves response status on adapted responses', async () => {
+        const posts = [{ id: 's', media_attachments: [] }];
+        const { fetch } = loadAdapter(() => jsonResponse(posts, { status: 201 }));
+
+        const res = await fetch(TIMELINE_URL);
+
+        assert.strictEqual(res.status, 201);
+        assert.deepStrictEqual(await res.json(), posts);
+    });
+});
diff --git a/tests/js/run.js b/tests/js/run.js
new file mode 100644
index 0000000..6d67f30
--- /dev/null
+++ b/tests/js/run.js
@@ -0,0 +1,45 @@
+#!/usr/bin/env node
+/**
+ * Lanceur des tests unitaires JS.
+ *
+ * Utilise le runner natif de Node (node:test), aucune dépendance npm.
+ * Usage : node tests/js/run.js
+ */
+'use strict';
+
+const { run } = require('node:test');
+const { spec } = require('node:test/reporters');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const testDir = __dirname;
+const files = fs
+    .readdirSync(testDir)
+    .filter((name) => name.endsWith('-test.js'))
+    .sort()
+    .map((name) => path.join(testDir, name));
+
+if (files.length === 0) {
+    console.error('Aucun fichier *-test.js trouvé dans ' + testDir);
+    process.exit(1);
+}
+
+const stream = run({ files });
+
+let failures = 0;
+stream.on('test:fail', () => {
+    failures += 1;
+});
+
+stream.on('error', (err) => {
+    console.error(err);
+    process.exitCode = 1;
+});
+
+stream.compose(spec).pipe(process.stdout);
+
+stream.on('end', () => {
+    if (failures > 0) {
+        process.exitCode = 1;
+    }
+});