From cb373f951fb3f34b9e54793687de14000a2dc08e Mon Sep 17 00:00:00 2001
From: xobotyi <xog3@yandex.ru>
Date: Mon, 4 Nov 2019 11:10:37 +0300
Subject: [PATCH] feat(usePreviousDistinct): add tests for undefined value
 behaviour;

---
 src/__tests__/usePreviousDistinct.test.tsx | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/__tests__/usePreviousDistinct.test.tsx b/src/__tests__/usePreviousDistinct.test.tsx
index 8bb7c04016..1a24d7b4c1 100644
--- a/src/__tests__/usePreviousDistinct.test.tsx
+++ b/src/__tests__/usePreviousDistinct.test.tsx
@@ -47,6 +47,23 @@ describe('usePreviousDistinct', () => {
     expect(hook.result.current).toBe(2);
   });
 
+  it('should work fine with `undefined` values', () => {
+    const hook = renderHook(({ value }) => usePreviousDistinct(value), {
+      initialProps: { value: undefined as undefined | number },
+    });
+
+    expect(hook.result.current).toBeUndefined();
+
+    hook.rerender({ value: 1 });
+    expect(hook.result.current).toBeUndefined();
+
+    hook.rerender({ value: undefined });
+    expect(hook.result.current).toBe(1);
+
+    hook.rerender({ value: 2 });
+    expect(hook.result.current).toBeUndefined();
+  });
+
   it('should receive a predicate as a second parameter that will compare prev and current', () => {
     const obj1 = { label: 'John', value: 'john' };
     const obj2 = { label: 'Jonny', value: 'john' };