Writing unit tests
Unit tests are written to test individual units of code, such as methods and classes. Unit tests are typically written by developers who are familiar with the code. When developers develop new features or fix bugs, they should also write unit tests to ensure that the code works as expected. There are many unit testing frameworks available for .NET, including NUnit, xUnit, and MSTest. In this chapter, we will use xUnit to write unit tests since it is one of the most popular unit testing frameworks for modern .NET applications at present.
Preparing the sample application
The sample application, InvoiceApp, is a simple ASP.NET Core web API application that exposes a set of RESTful APIs for managing invoices. The sample application uses EF Core to store and retrieve data from a SQL Server database. It has the following endpoints:
