diff --git a/tests/helpers/api_mock.ts b/tests/helpers/api_mock.ts
new file mode 100644
index 0000000..686f32d
--- /dev/null
+++ b/tests/helpers/api_mock.ts
@@ -0,0 +1,56 @@
+// Mock de fetch() pour les tests
+
+// deno-lint-ignore no-explicit-any
+let _originalFetch: ((input: any, init?: any) => Promise<Response>) | null =
+  null;
+
+/**
+ * Remplace globalThis.fetch par un mock qui retourne des réponses
+ * pré-configurées selon l'URL.
+ *
+ * @param routes - Map URL pattern → données de réponse (sera sérialisé en JSON)
+ */
+export function mockFetch(
+  routes: Record<string, unknown>,
+): void {
+  _originalFetch = globalThis.fetch;
+
+  globalThis.fetch = (
+    input: string | URL | Request,
+    _init?: RequestInit,
+  ): Promise<Response> => {
+    const url = typeof input === "string"
+      ? input
+      : input instanceof URL
+      ? input.toString()
+      : input.url;
+
+    for (const [pattern, data] of Object.entries(routes)) {
+      if (url.includes(pattern)) {
+        return Promise.resolve(
+          new Response(JSON.stringify(data), {
+            status: 200,
+            headers: { "Content-Type": "application/json" },
+          }),
+        );
+      }
+    }
+
+    return Promise.resolve(
+      new Response(JSON.stringify({ error: "Not Found" }), {
+        status: 404,
+        headers: { "Content-Type": "application/json" },
+      }),
+    );
+  };
+}
+
+/**
+ * Restaure le fetch original.
+ */
+export function restoreFetch(): void {
+  if (_originalFetch) {
+    globalThis.fetch = _originalFetch;
+    _originalFetch = null;
+  }
+}
diff --git a/tests/helpers/fixtures.ts b/tests/helpers/fixtures.ts
new file mode 100644
index 0000000..e63920e
--- /dev/null
+++ b/tests/helpers/fixtures.ts
@@ -0,0 +1,107 @@
+// Types et données de test pour l'API PolyMPR
+
+export interface Student {
+  numEtud: number;
+  nom: string;
+  prenom: string;
+  idPromo: number;
+}
+
+export interface Promotion {
+  idPromo: number;
+  annee: string;
+}
+
+export interface Prof {
+  id: number;
+  nom: string;
+  prenom: string;
+}
+
+export interface Module {
+  id: number;
+  nom: string;
+}
+
+export interface Note {
+  note: number;
+  numEtud: number;
+  idModule: number;
+}
+
+export interface UE {
+  id: number;
+  nom: string;
+}
+
+export interface UeModule {
+  idModule: number;
+  idUE: number;
+  idPromo: number;
+  coeff: number;
+}
+
+export interface Enseignement {
+  idProf: number;
+  idModule: number;
+  idPromo: number;
+}
+
+export interface Ajustement {
+  numEtud: number;
+  idUE: number;
+  valeur: number;
+}
+
+// --- Fixtures ---
+
+export const students: Student[] = [
+  { numEtud: 1, nom: "Dupont", prenom: "Alice", idPromo: 1 },
+  { numEtud: 2, nom: "Martin", prenom: "Bob", idPromo: 1 },
+  { numEtud: 3, nom: "Durand", prenom: "Claire", idPromo: 2 },
+];
+
+export const promotions: Promotion[] = [
+  { idPromo: 1, annee: "2025-2026" },
+  { idPromo: 2, annee: "2024-2025" },
+];
+
+export const profs: Prof[] = [
+  { id: 1, nom: "Leclerc", prenom: "Jean" },
+  { id: 2, nom: "Moreau", prenom: "Sophie" },
+];
+
+export const modules: Module[] = [
+  { id: 1, nom: "Mathématiques" },
+  { id: 2, nom: "Informatique" },
+  { id: 3, nom: "Physique" },
+];
+
+export const notes: Note[] = [
+  { note: 15, numEtud: 1, idModule: 1 },
+  { note: 12, numEtud: 1, idModule: 2 },
+  { note: 18, numEtud: 2, idModule: 1 },
+  { note: 9, numEtud: 3, idModule: 3 },
+];
+
+export const ues: UE[] = [
+  { id: 1, nom: "Sciences fondamentales" },
+  { id: 2, nom: "Sciences appliquées" },
+];
+
+export const ueModules: UeModule[] = [
+  { idModule: 1, idUE: 1, idPromo: 1, coeff: 3 },
+  { idModule: 2, idUE: 2, idPromo: 1, coeff: 4 },
+  { idModule: 3, idUE: 1, idPromo: 2, coeff: 2 },
+];
+
+export const enseignements: Enseignement[] = [
+  { idProf: 1, idModule: 1, idPromo: 1 },
+  { idProf: 2, idModule: 2, idPromo: 1 },
+  { idProf: 1, idModule: 3, idPromo: 2 },
+];
+
+export const ajustements: Ajustement[] = [
+  { numEtud: 1, idUE: 1, valeur: 0.5 },
+  { numEtud: 3, idUE: 1, valeur: -1 },
+];
diff --git a/tests/helpers/render.ts b/tests/helpers/render.ts
new file mode 100644
index 0000000..f87b1d9
--- /dev/null
+++ b/tests/helpers/render.ts
@@ -0,0 +1,55 @@
+// Setup happy-dom + wrapper render pour les tests de composants Preact
+
+import { Window } from "happy-dom";
+
+let _window: Window | null = null;
+
+/**
+ * Initialise un environnement DOM virtuel via happy-dom.
+ * À appeler avant de rendre des composants Preact dans les tests.
+ */
+export function setupDOM(): void {
+  _window = new Window({ url: "http://localhost" });
+
+  // Expose les globals DOM nécessaires à Preact
+  const globals = _window as unknown as Record<string, unknown>;
+  const target = globalThis as unknown as Record<string, unknown>;
+
+  for (
+    const key of [
+      "document",
+      "navigator",
+      "location",
+      "HTMLElement",
+      "HTMLInputElement",
+      "HTMLTextAreaElement",
+      "HTMLSelectElement",
+      "Event",
+      "CustomEvent",
+      "KeyboardEvent",
+      "MouseEvent",
+      "InputEvent",
+      "MutationObserver",
+      "requestAnimationFrame",
+      "cancelAnimationFrame",
+    ]
+  ) {
+    target[key] = globals[key];
+  }
+
+  target["window"] = _window;
+}
+
+/**
+ * Nettoie l'environnement DOM.
+ * À appeler dans un afterEach ou à la fin d'un test.
+ */
+export function cleanupDOM(): void {
+  if (_window) {
+    const doc = _window.document;
+    doc.body.innerHTML = "";
+    doc.head.innerHTML = "";
+    _window.close();
+    _window = null;
+  }
+}