Open the Business Application Studio and navigate to your project.
Create a new file with ".cds" extension and define the data model using the CDS (Core Data Services) language.
Right-click on the ".cds" file and select "Run as" > "OData V4 Service". This will start a local development server and make the OData service available at a URL.
Use a tool such as Postman or the browser's network inspector to send HTTP requests to the service and inspect the responses. You can perform various CRUD (Create, Read, Update, Delete) operations on the data to verify that the service is working as expected.
In case you need to test the OData service in a more automated way, you can write tests using the CAPM test framework or a different testing framework of your choice.