Create test suite for core functionality

__tests__/01_basic.spec.tsx

@@ -0,0 +1,58 @@
+import { create } from 'zustand';
+import { createSlice, withSlices } from '../src/index';
+
+describe('basic spec', () => {
+  it('should export functions', () => {
+    expect(createSlice).toBeDefined();
+    expect(withSlices).toBeDefined();
+  });
+  describe('createSlice', () => {
+    it('should return a slice config', () => {
+      const slice = createSlice({
+        name: 'counter',
+        value: 0,
+        actions: {
+          increment: () => (prev) => prev + 1,
+        },
+      });
+      // returns the input
+      expect(createSlice(slice)).toBe(slice);
+    });
+  });
+  describe('withSlices', () => {
+    it('should combine slices and nest state', () => {
+      const countSlice = createSlice({
+        name: 'count',
+        value: 0,
+        actions: {
+          inc: () => (prev) => prev + 1,
+          reset: () => () => 0,
+        },
+      });
+
+      const textSlice = createSlice({
+        name: 'text',
+        value: 'Hello',
+        actions: {
+          updateText: (newText: string) => () => newText,
+          reset: () => () => 'Hello',
+        },
+      });
+
+      const combinedConfig = withSlices(countSlice, textSlice);
+
+      expect(combinedConfig).toBeInstanceOf(Function);
+
+      const store = create(combinedConfig);
+
+      const state = store.getState();
+
+      expect(state.count).toBe(countSlice.value);
+      expect(state.text).toBe(textSlice.value);
+
+      expect(state.inc).toBeInstanceOf(Function);
+      expect(state.reset).toBeInstanceOf(Function);
+      expect(state.updateText).toBeInstanceOf(Function);
+    });
+  });
+});

__tests__/03_component.spec.tsx

@@ -0,0 +1,153 @@
+import { ReactNode, createContext, useContext, useState } from 'react';
+import { StoreApi, create, useStore as useZustandStore } from 'zustand';
+// eslint-disable-next-line import/no-extraneous-dependencies
+import { render, RenderOptions } from '@testing-library/react';
+// eslint-disable-next-line import/no-extraneous-dependencies
+import userEvent from '@testing-library/user-event';
+import { createSlice, withSlices } from '../src/index';
+
+type ExtractState<S> = S extends {
+  getState: () => infer State;
+}
+  ? State
+  : never;
+
+function createZustandContext<Store extends StoreApi<any>>(
+  makeStore: () => Store,
+) {
+  const Context = createContext<Store | undefined>(undefined);
+  const StoreProvider = ({ children }: { children: ReactNode }) => {
+    const [store] = useState(makeStore);
+    return <Context.Provider value={store}>{children}</Context.Provider>;
+  };
+  function useStore() {
+    const store = useContext(Context);
+    if (!store) {
+      throw new Error('useStore must be used within a StoreProvider');
+    }
+    return store;
+  }
+  function useSelector<Selected>(
+    selector: (state: ExtractState<Store>) => Selected,
+  ) {
+    const store = useStore();
+    return useZustandStore(store, selector);
+  }
+  return { StoreProvider, useStore, useSelector };
+}
+
+const countSlice = createSlice({
+  name: 'count',
+  value: 0,
+  actions: {
+    inc: () => (state) => state + 1,
+    reset: () => () => 0,
+  },
+});
+
+const textSlice = createSlice({
+  name: 'text',
+  value: 'Hello',
+  actions: {
+    updateText: (text: string) => () => text,
+    reset: () => () => 'Hello',
+  },
+});
+
+const makeStore = () => create(withSlices(countSlice, textSlice));
+
+const { StoreProvider, useStore, useSelector } =
+  createZustandContext(makeStore);
+
+const renderWithProvider = (
+  ui: ReactNode,
+  options?: Omit<RenderOptions, 'wrapper'>,
+) => render(ui, { wrapper: StoreProvider, ...options });
+
+const Counter = () => {
+  const count = useSelector((state) => state.count);
+  const { inc } = useStore().getState();
+  return (
+    <div>
+      <p data-testid="count">{count}</p>
+      <button type="button" onClick={inc}>
+        Increment
+      </button>
+    </div>
+  );
+};
+
+const Text = () => {
+  const text = useSelector((state) => state.text);
+  const { updateText } = useStore().getState();
+  return (
+    <div>
+      <input value={text} onChange={(e) => updateText(e.target.value)} />
+    </div>
+  );
+};
+
+const App = () => {
+  const { reset } = useStore().getState();
+  return (
+    <div>
+      <Counter />
+      <Text />
+      <button type="button" onClick={reset}>
+        Reset
+      </button>
+    </div>
+  );
+};
+
+describe('component spec', () => {
+  const user = userEvent.setup();
+  it('should render the app', () => {
+    const { getByRole, getByTestId } = renderWithProvider(<App />);
+    expect(getByTestId('count')).toHaveTextContent('0');
+    expect(getByRole('textbox')).toBeInTheDocument();
+  });
+  it('should increment the count when the button is pressed', async () => {
+    const { getByRole, getByTestId } = renderWithProvider(<App />);
+
+    const count = getByTestId('count');
+    expect(count).toHaveTextContent('0');
+
+    const button = getByRole('button', { name: 'Increment' });
+    await user.click(button);
+
+    expect(count).toHaveTextContent('1');
+  });
+  it('should update the text when the input is changed', async () => {
+    const { getByRole } = renderWithProvider(<App />);
+
+    const input = getByRole('textbox');
+    expect(input).toHaveValue('Hello');
+
+    await user.type(input, ' World');
+
+    expect(input).toHaveValue('Hello World');
+  });
+  it('should reset the state when the reset button is pressed', async () => {
+    const { getByRole, getByTestId } = renderWithProvider(<App />);
+
+    const resetButton = getByRole('button', { name: 'Reset' });
+
+    const count = getByTestId('count');
+    expect(count).toHaveTextContent('0');
+
+    const incrementButton = getByRole('button', { name: 'Increment' });
+    await user.click(incrementButton);
+    expect(count).toHaveTextContent('1');
+
+    const input = getByRole('textbox');
+    await user.type(input, ' World');
+    expect(input).toHaveValue('Hello World');
+
+    await user.click(resetButton);
+
+    // both slices reset because the action name is the same
+    expect(count).toHaveTextContent('0');
+    expect(input).toHaveValue('Hello');
+  });
+});

package.json

@@ -35,7 +35,10 @@
   },
   "jest": {
     "testEnvironment": "jsdom",
-    "preset": "ts-jest/presets/js-with-ts"
+    "preset": "ts-jest/presets/js-with-ts",
+    "setupFilesAfterEnv": [
+      "./test-setup.ts"
+    ]
   },
   "keywords": [
     "react",
@@ -44,6 +47,9 @@
   ],
   "license": "MIT",
   "devDependencies": {
+    "@testing-library/jest-dom": "^6.4.2",
+    "@testing-library/react": "^15.0.2",
+    "@testing-library/user-event": "^14.5.2",
     "@types/jest": "^29.5.12",
     "@types/node": "^20.12.7",
     "@types/react": "^18.2.79",