# Date Picker Testing Strategy

This document outlines the testing strategy for the date picker component to ensure quality and prevent regressions.

## Test Structure

The tests are organized into the following categories:

### 1. Unit Tests

Unit tests verify that individual functions and services work correctly in isolation:

- **Utils Tests**: Tests for utility functions in `calendar.utils.ts`
- **Service Tests**: Tests for each service (e.g., DateValidationService, CalendarGeneratorService)
- **Controller Tests**: Tests for the main controller class

### 2. Integration Tests

Integration tests verify that components work together correctly:

- **Controller Integration**: Tests that use the controller in ways similar to real application usage

## Running Tests

To run all tests:

```bash
npm test
```

To run tests in watch mode (continually watching for changes):

```bash
npm run test:watch
```

## Test Coverage

To generate a coverage report:

```bash
npm test -- --coverage
```

## Test Philosophy

Our testing strategy follows these principles:

1. **Test behavior, not implementation**: Tests should verify what components do, not how they do it.
2. **Edge cases first**: Focus on boundary conditions and edge cases.
3. **Fast feedback**: Tests should run quickly to provide immediate feedback.
4. **Isolation**: Unit tests should not depend on external services.

## Mocking Strategies

- **Date mocking**: The `mockDate` utility ensures that tests have a consistent date context.
- **Service dependencies**: Services are isolated by providing mock implementations of their dependencies.