From 46058a6998f21b80679345663ccfccd4ed8a1c38 Mon Sep 17 00:00:00 2001
From: Som Shekhar Mukherjee <iamssmkhrj@gmail.com>
Date: Wed, 7 May 2025 21:16:09 +0530
Subject: [PATCH] test: add tests for useLeaveDetection

---
 lib/tests/hooks/useLeaveDetection.test.tsx | 70 ++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 lib/tests/hooks/useLeaveDetection.test.tsx

diff --git a/lib/tests/hooks/useLeaveDetection.test.tsx b/lib/tests/hooks/useLeaveDetection.test.tsx
new file mode 100644
index 0000000..477b96e
--- /dev/null
+++ b/lib/tests/hooks/useLeaveDetection.test.tsx
@@ -0,0 +1,70 @@
+import { fireEvent, render, renderHook, screen } from '@testing-library/react';
+import { useLeaveDetection } from '../../hooks/useLeaveDetection';
+import { useState } from 'react';
+
+describe('useLeaveDetection', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should call the passed callback when the mouse leaves the document', () => {
+    const callback = jest.fn();
+    renderHook(() => useLeaveDetection(callback));
+
+    fireEvent.mouseLeave(document.documentElement);
+    expect(callback).toHaveBeenCalledTimes(1);
+  });
+
+  it('should setup the event listener only once', () => {
+    const spy = jest.spyOn(document.documentElement, 'addEventListener');
+    const { rerender } = renderHook(() => useLeaveDetection(() => {}));
+
+    rerender();
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy).toHaveBeenCalledWith('mouseleave', expect.any(Function));
+  });
+
+  it('should remove the event listener on unmount', () => {
+    const spy = jest.spyOn(document.documentElement, 'removeEventListener');
+    const callback = jest.fn();
+    const { unmount } = renderHook(() => useLeaveDetection(callback));
+
+    unmount();
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy).toHaveBeenCalledWith('mouseleave', expect.any(Function));
+
+    fireEvent.mouseLeave(document.documentElement);
+    expect(callback).toHaveBeenCalledTimes(0);
+  });
+
+  it('should always invoke the latest callback', () => {
+    const Test = () => {
+      const [count, setCount] = useState(0);
+      useLeaveDetection(() => setCount(count + 1));
+      return <div>{count}</div>;
+    };
+    render(<Test />);
+
+    expect(screen.getByText('0')).toBeInTheDocument();
+
+    fireEvent.mouseLeave(document.documentElement);
+    expect(screen.getByText('1')).toBeInTheDocument();
+
+    fireEvent.mouseLeave(document.documentElement);
+    expect(screen.getByText('2')).toBeInTheDocument();
+
+    fireEvent.mouseLeave(document.documentElement);
+    expect(screen.getByText('3')).toBeInTheDocument();
+  });
+
+  it('should invoke the callback with correct argument and `this` context', () => {
+    const callback = function (this: HTMLElement, ev: MouseEvent) {
+      expect(this).toBe(document.documentElement);
+      expect(ev).toBeInstanceOf(MouseEvent);
+      expect(ev.type).toBe('mouseleave');
+    };
+    renderHook(() => useLeaveDetection(callback));
+
+    fireEvent.mouseLeave(document.documentElement);
+  });
+});