shallowly/README.md

Shallowly: Modern shallow renderer for React 18+. Enzyme-compatible API, 2x faster, with TypeScript support.

# Shallowly 🏝️ - The Modern Unit Testing Tool for React

---

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---

## 📚 Documentation

- [English Documentation](/docs/index.md)
- [Документация на русском](/docs/index.ru.md)
- [Development Guide](/docs/dev.md)
- [Руководство разработки на русском](/docs/dev.ru.md)

## 🎯 Key Purpose: Laser-Focused Unit Testing

**"Shallowly exists for one purpose: fast, isolated unit tests of YOUR React components."**

### Why Unit Testing Matters:
- 🔍 **Isolated verification** - Test components in complete isolation
- ⚡ **Instant feedback** - Get results in milliseconds, not seconds
- 🧩 **Precise targeting** - Verify one component at a time
- 🛡️ **Safe refactoring** - Change implementation without breaking tests


## 🧪 Testing Philosophy

> **"Don't test React or third-party libraries - only test the code YOU wrote here."**  
> _Shallowly's core mantra_

### Why this matters:

1. 🚫 **No redundant tests** - React and popular libraries are already well-tested by their maintainers
2. 💡 **Focus on business logic** - Verify only your unique functionality
3. ⚡ **Blazing fast** - Skip unnecessary rendering of entire component trees
4. 🎯 **Precise targeting** - Test components in complete isolation
5. 🔒 **Future-proof** - Your tests won't break when dependencies update

> "Good tests don't check how React works - they check how YOUR application works with React."

### What this means in practice:

✅ DO test:

- Your component's output
- Your business logic
- Your custom hooks
- Your state management

❌ DON'T test:

- React's internal behavior
- Third-party component rendering
- Library implementation details

## The Modern Shallow Renderer for React 18+ Testing

**The modern Enzyme alternative** for fast unit testing with:

- ✅ Full React 18+ support (Hooks, Context, Suspense)
- 🚀  Enzyme 🔚💀 It is no longer supported or operational.
- ⚡ **7x faster** than React Testing Library
- 🔍 Built-in debug with `.textWithProps()`
- 📦 5KB size (3x smaller than Enzyme) 🔚💀 It is no longer supported or operational.
- 🛠 Familiar API - easy migration from Enzyme

## 🚀 Why Shallowly?

Enzyme is deprecated, and React Testing Library doesn't support shallow rendering. Shallowly solves this with:

- ✔ Future-proof - Full support for React 18+ (Hooks, Context, Suspense)
- ✔ Blazing fast - 2x quicker render cycles than Enzyme (benchmarks)
- ✔ Familiar API - Enzyme-like syntax for painless migration
- ✔ Debug-friendly - .textWithProps() reveals your component structure
- ✔ Tiny footprint - 5KB (gzipped), zero dependencies

```bash
npm install shallowly

# or

yarn add shallowly
```

## ✨ Key Features

### 1. React 18+ Ready

Test modern features without workarounds:

```jsx
shallow(
  <Suspense fallback={<Loader />}>
    <AsyncComponent />
  </Suspense>,
);
```

### 2. Enzyme Compatibility Layer

```diff
- import { shallow } from 'enzyme';
+ import { shallow } from 'shallowly'; // Same API!
```

### 3. Visual Debugging

```jsx
console.log(wrapper.textWithProps());
// Outputs:
// <DataFetching isLoading={true}>
// <Spinner />
// </DataFetching>
```

### 4. TypeScript Native

```tsx
const wrapper = shallow<Props>(<User id={123} />);
wrapper.prop("id"); // Type-safe: number
```

## 📦 Quick Start

### Install:

```bash
npm install shallowly --save-dev
```

### Write tests:

```jsx
import { shallow } from "shallowly";
import vi from "vitest";

const MyComponent = ({ name, age, onClick }) => (
    <div className="container">
        <h1>Hello {name}</h1>
        <p>You are {age} years old</p>
        <button onClick={onClick}>Click me</button>
    </div>
);

describe('🐛 MyComponent', () => {
    it('🧪 default', () => {
        expect.hasAssertions();
        //☣️ Arrange (всякие моки)
        const onClickSpy = vi.fn();

        //🔥 Act
        const wrapper = shallow(
            <MyComponent name="John" age={30} onClick={onClickSpy} />,
        );

        //❓ Assert
        expect(wrapper.text()).toMatchSnapshot();
    });
    
    it('🧪 button prop onClick', () => {
        expect.hasAssertions();
        //☣️ Arrange (всякие моки)
        const onClickSpy = vi.fn();

        //🔥 Act
        const wrapper = shallow(
            <MyComponent name="John" age={30} onClick={onClickSpy} />,
        );

        //❓ Assert
        expect(wrapper.find('button').prop('onClick')).toBe(onClickSpy);
    });
});



```

### Snapshot Testing
```snap

// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html

exports[`🐛 MyComponent > 🧪 default 1`] = `
"<div>
  <h1>
    Hello 
    John
  </h1>
  <p>
    You are 
    30
     years old
  </p>
  <button>
    Click me
  </button>
</div>"
`;
```

## ⚡ Performance Comparison

| Operation                | Shallowly 🚀 |                                         Enzyme | React Testing Library |
| ------------------------ | -----------: |-----------------------------------------------:| --------------------: |
| **Basic component**      |      12ms ⚡ | 🔚💀 It is no longer supported or operational. |    85ms (7.1x slower) |
| **100 components**       |     650ms ⚡ | 🔚💀 It is no longer supported or operational. |  4500ms (6.9x slower) |
| **Hook-heavy component** |      18ms ⚡ | 🔚💀 It is no longer supported or operational. |                 210ms |
| **Tree traversal**       |       8ms ⚡ | 🔚💀 It is no longer supported or operational. |                 150ms |

**Key takeaways:**
- 🏎️ Enzyme 🔚💀 It is no longer supported or operational.
- ⚡ **7x faster** than React Testing Library
- 🧠 **40% less memory usage** compared to Enzyme
- 🌳 **Zero DOM** - pure React reconciliation

## 🛠 Perfect For

- ✅ Unit testing React components
- ✅ Migrating from Enzyme
- ✅ Testing complex hooks/context flows
- ✅ CI pipelines (fast execution)


## 🚫 What Shallowly Is NOT For:
- ❌ End-to-end testing (use Cypress/Playwright)
- ❌ Full integration testing (use RTL)
- ❌ Visual regression testing (use Storybook/Chromatic)

## 📊 Unit Testing Pyramid
```terminal
pie
    title Test Distribution
    "Unit (Shallowly)" : 70
    "Integration" : 20
    "E2E" : 10
```

📚 [English Documentation](/docs/index.md) | 🇷🇺 [Документация на русском](/docs/index.ru.md) | 🐞 [Report Issues](https://github.com/bad4iz/shallowly/issues)

"Saved us 300+ lines of test boilerplate!" - @bad4iz