diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..b954dcc
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,22 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - '*'
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22.12.0'
+      - name: Install dependencies
+        run: npm install
+      - name: Run unit tests
+        run: npm run test -- --watch=false --browsers=ChromeHeadless
+        env:
+          CHROME_BIN: /usr/bin/google-chrome
diff --git a/src/app/annotation-templates.service.spec.ts b/src/app/annotation-templates.service.spec.ts
new file mode 100644
index 0000000..159528f
--- /dev/null
+++ b/src/app/annotation-templates.service.spec.ts
@@ -0,0 +1,139 @@
+import { TestBed } from '@angular/core/testing';
+import {
+  AnnotationTemplate,
+  AnnotationTemplatesService,
+} from './annotation-templates.service';
+import { PageAnnotations } from './models/annotation.model';
+
+const TEMPLATES_KEY = 'pdf-annotator.templates';
+
+class MockStorage implements Storage {
+  private store = new Map<string, string>();
+
+  get length(): number {
+    return this.store.size;
+  }
+
+  clear(): void {
+    this.store.clear();
+  }
+
+  getItem(key: string): string | null {
+    return this.store.has(key) ? this.store.get(key)! : null;
+  }
+
+  key(index: number): string | null {
+    return Array.from(this.store.keys())[index] ?? null;
+  }
+
+  removeItem(key: string): void {
+    this.store.delete(key);
+  }
+
+  setItem(key: string, value: string): void {
+    this.store.set(key, value);
+  }
+}
+
+class QuotaExceededStorage extends MockStorage {
+  override setItem(): void {
+    throw new DOMException('Storage quota exceeded', 'QuotaExceededError');
+  }
+}
+
+describe('AnnotationTemplatesService', () => {
+  const originalLocalStorage = window.localStorage;
+  let service: AnnotationTemplatesService;
+  let storage: MockStorage;
+  let localStorageGetterSpy!: jasmine.Spy<() => Storage>;
+
+  function stubLocalStorage(value: Storage | undefined) {
+    localStorageGetterSpy.and.callFake(() => value as unknown as Storage);
+  }
+
+  beforeAll(() => {
+    localStorageGetterSpy = spyOnProperty(window, 'localStorage', 'get');
+  });
+
+  beforeEach(() => {
+    storage = new MockStorage();
+    stubLocalStorage(storage);
+
+    TestBed.configureTestingModule({
+      providers: [AnnotationTemplatesService],
+    });
+
+    service = TestBed.inject(AnnotationTemplatesService);
+  });
+
+  afterEach(() => {
+    stubLocalStorage(originalLocalStorage);
+  });
+
+  afterAll(() => {
+    localStorageGetterSpy.and.callThrough();
+  });
+
+  function createTemplate(id: string, name: string): AnnotationTemplate {
+    return {
+      id,
+      name,
+      createdAt: Date.now(),
+      pages: [],
+    };
+  }
+
+  it('should return the default template first even when stored templates exist', () => {
+    const existingTemplate = createTemplate('stored-id', 'Guardada');
+    storage.setItem(TEMPLATES_KEY, JSON.stringify([existingTemplate]));
+
+    const templates = service.getTemplates();
+
+    expect(templates[0].id).toBe(service.defaultTemplateId);
+    expect(templates[1]).toEqual(jasmine.objectContaining({ id: 'stored-id', name: 'Guardada' }));
+  });
+
+  it('should normalize template names and update existing templates', () => {
+    const initialPages: PageAnnotations[] = [{ num: 1, fields: [] }];
+    const updatedPages: PageAnnotations[] = [{ num: 2, fields: [] }];
+
+    const created = service.saveTemplate('  Plantilla Personalizada  ', initialPages);
+    expect(created).not.toBeNull();
+    expect(created!.name).toBe('Plantilla Personalizada');
+
+    const updated = service.saveTemplate('plantilla personalizada', updatedPages);
+    expect(updated).not.toBeNull();
+    expect(updated!.id).toBe(created!.id);
+    expect(updated!.pages).toEqual(updatedPages);
+    expect(updated!.name).toBe('plantilla personalizada');
+
+    const storedRaw = storage.getItem(TEMPLATES_KEY);
+    expect(storedRaw).toBeTruthy();
+    const storedTemplates = JSON.parse(storedRaw!) as AnnotationTemplate[];
+    expect(storedTemplates.length).toBe(1);
+    expect(storedTemplates[0].name).toBe('plantilla personalizada');
+    expect(storedTemplates[0].pages).toEqual(updatedPages);
+  });
+
+  it('should return null when saving without localStorage support', () => {
+    stubLocalStorage(undefined);
+
+    const result = service.saveTemplate('Sin almacenamiento', []);
+
+    expect(result).toBeNull();
+  });
+
+  it('should handle quota exceeded errors without throwing', () => {
+    const quotaStorage = new QuotaExceededStorage();
+    stubLocalStorage(quotaStorage);
+    const warnSpy = spyOn(console, 'warn');
+
+    const result = service.saveTemplate('Quota', []);
+
+    expect(result).not.toBeNull();
+    expect(warnSpy).toHaveBeenCalledWith(
+      'Storage quota exceeded, persistence disabled for key:',
+      TEMPLATES_KEY
+    );
+  });
+});