Add DataDog tests

src/components/DataDog/DataDog.test.tsx

@@ -0,0 +1,59 @@
+import { render } from '@testing-library/react';
+import { useSession } from 'next-auth/react';
+import TestRouter from '__tests__/util/TestRouter';
+import { setDataDogUser } from 'src/lib/dataDog';
+import DataDog from './DataDog';
+
+jest.mock('src/lib/dataDog');
+
+const accountListId = 'account-list-1';
+const router = {
+  query: { accountListId },
+  isReady: true,
+};
+
+const TestComponent: React.FC = () => (
+  <TestRouter router={router}>
+    <DataDog />
+  </TestRouter>
+);
+
+describe('DataDog', () => {
+  it('calls setDataDogUser with the user', () => {
+    render(<TestComponent />);
+
+    expect(setDataDogUser).toHaveBeenCalledWith({
+      accountListId: 'account-list-1',
+      email: '[email protected]',
+      name: 'First Last',
+      userId: 'user-1',
+    });
+  });
+
+  it('does not call setDataDogUser if there is no session', () => {
+    (useSession as jest.MockedFn<typeof useSession>).mockReturnValueOnce({
+      data: null,
+      status: 'unauthenticated',
+      update: () => Promise.resolve(null),
+    });
+
+    render(<TestComponent />);
+
+    expect(setDataDogUser).not.toHaveBeenCalled();
+  });
+
+  it('handles missing accountListId', () => {
+    render(
+      <TestRouter router={{ query: {}, isReady: true }}>
+        <DataDog />
+      </TestRouter>,
+    );
+
+    expect(setDataDogUser).toHaveBeenCalledWith({
+      accountListId: null,
+      email: '[email protected]',
+      name: 'First Last',
+      userId: 'user-1',
+    });
+  });
+});