An example of how to use appsettings in NUnit

TestUtilities.cs

using NUnit.Framework;

namespace Jaber.Tests
{
    using Microsoft.Extensions.Configuration;

    /// <summary>
    /// Just an example class that contains my special configuration
    /// </summary>
    public class MySpecialConfig
    {
        public bool EnableSomething { get; set; }
        public int Timeout { get; set; }
    }

    /// <summary>
    /// A simple class to demonstrate access to appsettings.json
    /// </summary>
    public static class TestUtilities
    {
        /// <summary>
        /// The simplest approach
        /// </summary>
        /// <param name="basePath"></param>
        /// <returns><see cref="IConfigurationRoot"/></returns>
        /// <remarks>
        /// Requires 'Microsoft.Extensions.Configuration.Json'
        /// </remarks>
        /// <example>
        /// Usage with NUnit's <see cref="TestContext"/> 
        /// var configRoot = TestUtilities.GetConfiguration(TestContext.CurrentContext.TestDirectory);
        /// var myValue = configRoot["MySpecialConfig:Timeout"];
        /// </example>
        public static IConfigurationRoot GetConfiguration(string basePath)
        {
            return new ConfigurationBuilder()
                .SetBasePath(basePath)
                .AddJsonFile("appsettings.json", optional: true)
                // Optional
                //.AddEnvironmentVariables()
                .Build();
        }

        /// <summary>
        /// The type safe way
        /// </summary>
        /// <param name="basePath"></param>
        /// <param name="sectionName"></param>
        /// <returns>New instance of <see cref="MySpecialConfig"/></returns>
        /// <example>
        /// Usage with NUnit's <see cref="TestContext"/> 
        /// var myConfig = TestUtilities.GetMySpecialConfig(TestContext.CurrentContext.TestDirectory);
        /// var myValue = myConfig.Timeout;
        /// </example>
        public static MySpecialConfig GetMySpecialConfig(string basePath, string sectionName = nameof(MySpecialConfig))
        {
            var newInstance = new MySpecialConfig();

            var config = GetConfiguration(basePath);

            config
                .GetSection(sectionName)
                .Bind(newInstance);

            return newInstance;
        }

        /// <summary>
        /// Does it flexible and type safe
        /// Uses the convention "Section name == class name"
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="basePath"></param>
        /// <param name="sectionName"></param>
        /// <returns>New instance of <see cref="T"/></returns>
        /// <example>
        /// Requires 'Microsoft.Extensions.Configuration.Binder'
        /// Usage with NUnit's <see cref="TestContext"/> 
        /// var myConfig = TestUtilities.GetConfiguration<MyConfig>(TestContext.CurrentContext.TestDirectory);
        /// var myValue = myConfig.Timeout;
        /// </example>
        public static T GetConfiguration<T>(string basePath, string sectionName = null) where T : new()
        {
            var newInstance = new T();

            var config = GetConfiguration(basePath);

            config
                .GetSection(sectionName ?? typeof(T).Name)
                .Bind(newInstance);

            return newInstance;
        }
    }
}