Kata - Music Streaming Service

Kata: Music Streaming Service

# Music Streaming Service

## Scenario

Test-drive code that manages the catalog and subscriptions of a **digital music streaming service**. Customers can browse and search the catalog by title, artist, and genre. Record labels and independent artists submit their tracks to the platform, and the service maintains a catalog with details about each track, including the streaming rights and availability status.

### Key Features

1. **Track Availability**  
   - Maintain a count of how many streams are available for promotional tracks or limited-time releases.  
   - Ensure that users can only stream tracks that are available.

2. **Subscription Management**  
   - Customers must have an active subscription to stream tracks.  
   - Use dependency injection to fake credit card payment processing, allowing the focus to remain on designing the streaming service.

3. **Reviews and Ratings**  
   - Customers can leave reviews for tracks they've listened to.  
   - Reviews include a **rating** (1-10) and optional text feedback.

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### TDD Guidelines

Apply the following principles to ensure high-quality code:

- **Working**: Fully functional and passes all tests.
- **Easy to Understand**: Readable and maintainable for others.
- **Minimally Duplicated**: Avoid redundant code.
- **As Simple as Possible**: No unnecessary complexity.

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### Class Design Principles

Design classes that:

1. **Tell, don’t ask**  
   - Encapsulate behavior and data within cohesive objects.

2. **Have one distinct responsibility**  
   - Follow the Single Responsibility Principle.

3. **Can be composed from the outside**  
   - Enable flexible usage and integration.

4. **Expose client-specific interfaces**  
   - Tailor interfaces to specific client needs.

5. **Use contract tests for shared abstractions**  
   - Ensure reliable and reusable abstractions.

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