We helped our client to migrate a huge desktop Delphi app that has around 1600 functions and 3200 modules to the .NET web

The first pitfall we faced was the size of the software which turned out really big. It had 3200 modules and 1600 functions. It became obvious that testing them all manually after migration didn’t seem to be a feasible task. That’s why we developed custom software to organize the automated QA testing process. Unit testing was fully performed automatically. It presupposed comparing the requests and responses of the Delphi version with the new .NET version.

Given the complexity of the software architecture, we paid a lot of attention to such stages as Initial Business analysis and the development of a project migration plan. 

Before starting the migration itself we had to implement the first batch of REST API methods. We:

• defined the list of methods and models;
• described REST API using a web tool, exporting it to the Swagger file;
• generated the .NET/C# project from the Swagger file, and ensured the connection to a database.

And only after that, we could proceed to other sprints that presupposed conducting the step-by-step migration process with some sub-projects being migrated and tested in parallel.