feat: create use posts store initial and add tests

feat devhatt#30

src/stores/__mocks__/zunstandMock.ts

@@ -0,0 +1,14 @@
+import * as zustand from 'zustand';
+
+const actualCreate = zustand.create;
+export const storeResetFns = new Set<() => void>();
+export const myCustomCreate = <T>() => {
+  return (stateCreator: zustand.StateCreator<T>) => {
+    const store = actualCreate(stateCreator);
+    const initialState = store.getState();
+    storeResetFns.add(() => {
+      store.setState(initialState, true);
+    });
+    return store;
+  };
+};

src/stores/usePostsStore.test.tsx

@@ -0,0 +1,53 @@
+import { renderHook, act } from '@testing-library/react';
+import * as zustand from 'zustand';
+
+import { usePostsStore } from './usePostsStore';
+
+import { myCustomCreate, storeResetFns } from './__mocks__/zunstandMock';
+
+jest.spyOn(zustand, 'create').mockImplementation(myCustomCreate as never);
+
+describe('usePostsStore', () => {
+  afterEach(() => {
+    act(() => {
+      storeResetFns.forEach((resetFn) => {
+        resetFn();
+      });
+    });
+  });
+
+  describe('when initialize', () => {
+    it('posts should be zero', () => {
+      const { result } = renderHook(() => usePostsStore((state) => state));
+      expect(result.current.postsQuantity).toBe(0);
+    });
+  });
+
+  describe('when increased the number of posts', () => {
+    it('set value to tree', () => {
+      const { result } = renderHook(() => usePostsStore((state) => state));
+
+      act(() => {
+        result.current.increase(3);
+      });
+
+      expect(result.current.postsQuantity).toBe(3);
+    });
+  });
+
+  describe('when we reset the number of posts', () => {
+    it('change to tree and reset to zero', () => {
+      const { result } = renderHook(() => usePostsStore((state) => state));
+
+      act(() => {
+        result.current.increase(2);
+      });
+
+      act(() => {
+        result.current.reset();
+      });
+
+      expect(result.current.postsQuantity).toBe(0);
+    });
+  });
+});