diff --git a/src/components/GlobalModal/GlobalModal.test.tsx b/src/components/GlobalModal/GlobalModal.test.tsx
new file mode 100644
index 0000000..28897d9
--- /dev/null
+++ b/src/components/GlobalModal/GlobalModal.test.tsx
@@ -0,0 +1,134 @@
+import { render, screen } from '@testing-library/react';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+import * as GlobalModalCtx from '@/context/GlobalModalContext';
+
+import GlobalModal from './GlobalModal';
+
+const { modalState } = vi.hoisted(() => ({
+  modalState: { promptLogin: false as boolean, promptError: null as string | null },
+}));
+
+vi.mock('@/context/GlobalModalContext', () => {
+  const useGlobalModal = vi.fn(() => modalState);
+  return { useGlobalModal };
+});
+
+
+vi.mock('./Modals/LoginModal', () => ({
+  __esModule: true,
+  default: () => <div data-testid="mock-login-modal">LOGIN_MODAL</div>,
+}));
+vi.mock('./Modals/ErrorModal', () => ({
+  __esModule: true,
+  default: ({ errorMessageKey }: { errorMessageKey: string }) => (
+    <div data-testid="mock-error-modal">{errorMessageKey}</div>
+  ),
+}));
+
+const ensurePortalContainer = () => {
+  let container = document.getElementById('modal-container');
+  if (!container) {
+    container = document.createElement('div');
+    container.id = 'modal-container';
+    document.body.appendChild(container);
+  }
+  return container;
+};
+
+beforeEach(() => {
+  // reset DOM + state
+  document.body.innerHTML = '';
+  modalState.promptLogin = false;
+  modalState.promptError = null;
+
+  // reset context mock calls
+  (GlobalModalCtx.useGlobalModal as any).mockClear?.();
+});
+
+describe('GlobalModal', () => {
+  it('renders nothing when neither login nor error is requested', () => {
+    const container = ensurePortalContainer();
+
+    render(<GlobalModal />);
+
+    expect(GlobalModalCtx.useGlobalModal).toHaveBeenCalled();
+
+    // No modals in portal container nor body
+    expect(container.querySelector('[data-testid="mock-login-modal"]')).toBeNull();
+    expect(container.querySelector('[data-testid="mock-error-modal"]')).toBeNull();
+    expect(screen.queryByTestId('mock-login-modal')).toBeNull();
+    expect(screen.queryByTestId('mock-error-modal')).toBeNull();
+  });
+
+  it('renders LoginModal when promptLogin is true (into #modal-container)', () => {
+    const container = ensurePortalContainer();
+    modalState.promptLogin = true;
+
+    render(<GlobalModal />);
+
+    expect(GlobalModalCtx.useGlobalModal).toHaveBeenCalled();
+
+    // login modal should be inside the portal container
+    expect(container.querySelector('[data-testid="mock-login-modal"]')).not.toBeNull();
+    expect(container.querySelector('[data-testid="mock-error-modal"]')).toBeNull();
+  });
+
+  it('renders ErrorModal with message when promptError is set', () => {
+    const container = ensurePortalContainer();
+    modalState.promptError = 'some.error.key';
+
+    render(<GlobalModal />);
+
+    expect(GlobalModalCtx.useGlobalModal).toHaveBeenCalled();
+
+    const err = container.querySelector('[data-testid="mock-error-modal"]');
+    expect(err).not.toBeNull();
+    expect(err!.textContent).toBe('some.error.key');
+    expect(container.querySelector('[data-testid="mock-login-modal"]')).toBeNull();
+  });
+
+  it('prefers ErrorModal over LoginModal when both flags are set', () => {
+    const container = ensurePortalContainer();
+    modalState.promptLogin = true;
+    modalState.promptError = 'override.error';
+
+    render(<GlobalModal />);
+
+    expect(GlobalModalCtx.useGlobalModal).toHaveBeenCalled();
+
+    expect(container.querySelector('[data-testid="mock-error-modal"]')).not.toBeNull();
+    expect(container.querySelector('[data-testid="mock-login-modal"]')).toBeNull();
+  });
+
+  it('falls back to document.body when #modal-container is missing', () => {
+    // no ensurePortalContainer() → should portal to body
+    modalState.promptLogin = true;
+
+    render(<GlobalModal />);
+
+    expect(GlobalModalCtx.useGlobalModal).toHaveBeenCalled();
+
+    // login modal should exist in body (since there’s no container)
+    const login = document.body.querySelector('[data-testid="mock-login-modal"]');
+    expect(login).not.toBeNull();
+  });
+
+  it('rerenders correctly when state changes (login → error)', () => {
+    const container = ensurePortalContainer();
+    modalState.promptLogin = true;
+
+    const { rerender } = render(<GlobalModal />);
+    expect(container.querySelector('[data-testid="mock-login-modal"]')).not.toBeNull();
+    expect(container.querySelector('[data-testid="mock-error-modal"]')).toBeNull();
+
+    modalState.promptLogin = false;
+    modalState.promptError = 'err.key';
+    rerender(<GlobalModal />);
+
+    expect(container.querySelector('[data-testid="mock-login-modal"]')).toBeNull();
+    const err = container.querySelector('[data-testid="mock-error-modal"]');
+    expect(err).not.toBeNull();
+    expect(err!.textContent).toBe('err.key');
+  });
+});
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