Populate IConfiguration for unit tests

Question

.NET Core configuration allows so many options to add values (environment variables, json files, command line args).

I just can\'t figure out and find an answer how

Answer 1

I prefer not to have my application classes dependent on IConfiguration. Instead I create a configuration class to hold the config, with a constructor that can initialise it from IConfiguration like this:

public class WidgetProcessorConfig
{
    public int QueueLength { get; set; }
    public WidgetProcessorConfig(IConfiguration configuration)
    {
        configuration.Bind("WidgetProcessor", this);
    }
    public WidgetProcessorConfig() { }
}

then in your ConfigureServices, you just have to do:

services.AddSingleton();
services.AddSingleton();

and for testing:

var config = new WidgetProcessorConfig
{
    QueueLength = 18
};
var widgetProcessor = new WidgetProcessor(config);