Using ASP.NET Core's ConfigurationBuilder in a Test Project

Question

I want to use the IHostingEnvironment and ConfigurationBuilder in my functional test project, so that depending on the environment the functional tests run using a different set of configuration. I want to make use of the code below:

public IConfigurationRoot ConfigureConfiguration(IHostingEnvironment hostingEnvironment)
{
    var builder = new ConfigurationBuilder()
        .AddJsonFile("appsettings.json")
        .AddJsonFile($"appsettings.{hostingEnvironment.EnvironmentName}.json", true)
        .AddEnvironmentVariables();
    return builder.Build();
}

I want to have an appSettings.json and appSettings.Production.json file to point my functional tests at production. Is this possible? How can it be achieved? I would need an instance of IHostingEnvironment.

Answer 1

You can use the ConfigurationBuilder in a test project with a couple of steps. I don't think you will need the IHostingEnvironment interface itself.

First, add two NuGet packages to your project which have the ConfigurationBuilder extension methods:

"dependencies": {
  "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0-rc1-final",
  "Microsoft.Extensions.Configuration.Json": "1.0.0-rc1-final"
}

Second, put your desired environment variables into the test project's properties:

Then you can create your own builder in the test project:

private readonly IConfigurationRoot _configuration;

public BuildConfig()
{
    var environmentName = Environment.GetEnvironmentVariable("Hosting:Environment");

    var config = new ConfigurationBuilder()
        .AddJsonFile("appsettings.json")
        .AddJsonFile($"appsettings.{environmentName}.json", true)
        .AddEnvironmentVariables();

    _configuration = config.Build();
}

If you want to use precisely the same settings file (not a copy), then you'll need to add in a path to it.