Add comprehensive test coverage

package.json

@@ -35,15 +35,20 @@
   },
   "devDependencies": {
     "@arethetypeswrong/core": "^0.18.2",
+    "@testing-library/dom": "10.4.1",
+    "@testing-library/react": "16.3.2",
     "@types/node": "^24.0.0",
-    "@types/react": "^19.0.0",
+    "@types/react": "19.2.14",
+    "@types/react-dom": "19.2.3",
     "@vitest/browser-playwright": "^4.1.5",
     "lint-staged": "^16.4.0",
     "oxfmt": "^0.38.0",
     "oxlint": "^1.53.0",
     "oxlint-tsgolint": "^0.16.0",
     "playwright": "^1.49.0",
     "publint": "^0.3.18",
+    "react": "19.2.5",
+    "react-dom": "19.2.5",
     "tsdown": "^0.21.10",
     "typescript": "^6.0.2",
     "unplugin-unused": "^0.5.7",

src/__tests__/client.test.ts

@@ -0,0 +1,44 @@
+import { client } from '../client';
+
+describe('client', () => {
+  it('exports a singleton plugin instance', () => {
+    expect(client).toBeDefined();
+    expect(client.config).toBeDefined();
+    expect(client.elements).toBeDefined();
+    expect(client.style).toBeDefined();
+    expect(typeof client.destroy).toBe('function');
+  });
+
+  it('exposes the documented config methods', () => {
+    expect(typeof client.config.get).toBe('function');
+    expect(typeof client.config.set).toBe('function');
+    expect(typeof client.config.subscribe).toBe('function');
+    expect(typeof client.config.getVariable).toBe('function');
+    expect(typeof client.config.setVariable).toBe('function');
+    expect(typeof client.config.subscribeToWorkbookVariable).toBe('function');
+    expect(typeof client.config.getInteraction).toBe('function');
+    expect(typeof client.config.setInteraction).toBe('function');
+    expect(typeof client.config.subscribeToWorkbookInteraction).toBe(
+      'function',
+    );
+    expect(typeof client.config.triggerAction).toBe('function');
+    expect(typeof client.config.registerEffect).toBe('function');
+    expect(typeof client.config.configureEditorPanel).toBe('function');
+    expect(typeof client.config.setLoadingState).toBe('function');
+    expect(typeof client.config.getUrlParameter).toBe('function');
+    expect(typeof client.config.setUrlParameter).toBe('function');
+    expect(typeof client.config.subscribeToUrlParameter).toBe('function');
+  });
+
+  it('exposes the documented elements methods', () => {
+    expect(typeof client.elements.getElementColumns).toBe('function');
+    expect(typeof client.elements.subscribeToElementColumns).toBe('function');
+    expect(typeof client.elements.subscribeToElementData).toBe('function');
+    expect(typeof client.elements.fetchMoreElementData).toBe('function');
+  });
+
+  it('exposes the documented style methods', () => {
+    expect(typeof client.style.subscribe).toBe('function');
+    expect(typeof client.style.get).toBe('function');
+  });
+});

src/__tests__/error.test.ts

@@ -0,0 +1,63 @@
+import { validateConfigId } from '../error';
+
+describe('validateConfigId', () => {
+  let warnSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    warnSpy.mockRestore();
+  });
+
+  it('logs a warning when configId is undefined', () => {
+    validateConfigId(undefined as unknown as string, 'variable');
+    expect(warnSpy).toHaveBeenCalledTimes(1);
+    expect(warnSpy).toHaveBeenCalledWith('Invalid config variable: undefined');
+  });
+
+  it('does not warn for a defined configId', () => {
+    validateConfigId('id', 'variable');
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it('does not warn for an empty string configId', () => {
+    validateConfigId('', 'variable');
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it('does not warn for null configId (only undefined triggers a warning)', () => {
+    validateConfigId(null as unknown as string, 'variable');
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it('includes the expectedConfigType in the warning message', () => {
+    validateConfigId(undefined as unknown as string, 'element');
+    expect(warnSpy).toHaveBeenCalledWith('Invalid config element: undefined');
+
+    warnSpy.mockClear();
+    validateConfigId(undefined as unknown as string, 'url-parameter');
+    expect(warnSpy).toHaveBeenCalledWith(
+      'Invalid config url-parameter: undefined',
+    );
+
+    warnSpy.mockClear();
+    validateConfigId(undefined as unknown as string, 'action-trigger');
+    expect(warnSpy).toHaveBeenCalledWith(
+      'Invalid config action-trigger: undefined',
+    );
+
+    warnSpy.mockClear();
+    validateConfigId(undefined as unknown as string, 'action-effect');
+    expect(warnSpy).toHaveBeenCalledWith(
+      'Invalid config action-effect: undefined',
+    );
+
+    warnSpy.mockClear();
+    validateConfigId(undefined as unknown as string, 'interaction');
+    expect(warnSpy).toHaveBeenCalledWith(
+      'Invalid config interaction: undefined',
+    );
+  });
+});