Appendix 2: Advanced Mocking Scenarios

This book has numerous examples of straightforward mocking scenarios. And the good news is, in a clean code environment, implementing most of those mocking requirements will be easy.

However, there are times when you have to innovate a bit to be able to mock your desired class. I did not want to end this book without presenting you with a scenario, so here you go.

In this appendix, we will experience how to combine a fake with a mock to deal with a .NET class called HttpMessageHandler. By the end of this appendix, you will be familiar with more NSubstitute functionalities and ready to tackle more advanced mocking cases.

Technical requirements

The code for this chapter can be found at the following GitHub repository:

https://github.com/PacktPublishing/Pragmatic-Test-Driven-Development-in-C-Sharp-and-.NET/tree/main/appendix2

Writing an OpenWeather client library

We have used the OpenWeather service in this book frequently, so I will give you a quick reminder – OpenWeather provides a set of RESTful APIs to bring you the weather and the forecast.

To consume the service from a C# application, it is good to have a library that will translate RESTful API calls to C# and shield the developer from the little details of HTTP. We call this sort of library a RESTful client library or sometimes a software development kit (SDK).

We will build an SDK for this service using TDD (of course!) and, while doing so, we will encounter more advanced mocking requirements.

The One Call API

OpenWeather has an API called One Call that will get you today’s weather information and the forecast for the next few days. The best way to illustrate how this works is by using an example that gets the weather and the forecast for Greenwich, London.

First, issue a RESTful GET request. You can use your browser...

Further reading

To learn more about the topics discussed in the chapter, you can refer to OpenWeather’s official website: https://openweathermap.org