Legacy WinForms image editor refactored to a clean, 3‑layer architecture with 100 % business‑layer test coverage.

PictureEditor breathes new life into an outdated, tightly‑coupled WinForms image editor. The codebase has been systematically refactored—following Test‑Driven Development—to a Presentation ⇆ Business ⇆ Data layered model. Users can open common image formats, apply a small set of filters and edge‑detection algorithms, and save the result, while developers benefit from a fully covered and easily extensible codebase.

With the architecture solidified, both 100 % business‑layer unit tests and automated UI tests guarantee end‑to‑end behaviour.

• Business Layer – driven by xUnit and NSubstitute mocks, achieving 100 % line & branch coverage.
• UI Layer – validated by fully automated WinForms UI tests, ensuring reliable end‑to‑end coverage.

• Understand the benefits of a layered architecture on legacy code.
• Apply Test‑Driven Development to drive safe refactors.
• Implement dependency‑inversion via interfaces and DI.
• Achieve 100 % unit‑test coverage on the business layer.
• Develop automated tests for key WinForms UI elements to ensure end‑to‑end functionality.

• Load / Save images (JPG, PNG, BMP).
• Apply up to three colour filters (Black‑&‑White, Swap, Magic Mosaic).
• Run up to three edge‑detection algorithms (Sobel, Prewitt, …).

• ✅ Encapsulation & SOLID principles
• ✅ Dependency Injection
• ✅ Separation of Concerns

Standard C# try/catch blocks wrap disk and image operations; failures bubble up to the UI layer through typed exceptions.

WinForms UI (Presentation)
      │  IImageManager  IEdgeDetection  IOutputInput
      ▼
+----------------------------------------------+
|   Business Layer – 100 % unit‑test coverage  |
|  · FiltersManager     · EdgeDetectionManager |
|                ImageManager                  |
+----------------------------------------------+
      │
      ▼
OutputInputFilesystem (Data Access Layer)

• User & developer docs in Annexes/UserGuide.pdf.
• Project presentation slides in Annexes/Presentation.pptx.

• Arthur Avez
• Elias Borrajo
• Benjamin Keller

Project completed for HES‑SO Valais, Module 625‑1 — Test‑Driven Development (Fall 2023). Professor: Dominique Genoud