C# how to mock Configuration.GetSection(“foo:bar”).Get()

I was able to solve it using ConfigurationBuilder. Hope this will help

  var appSettings = @"{""AppSettings"":{
            ""Key1"" : ""Value1"",
            ""Key2"" : ""Value2"",
            ""Key3"" : ""Value3""
            }}";

  var builder = new ConfigurationBuilder();

  builder.AddJsonStream(new MemoryStream(Encoding.UTF8.GetBytes(appSettings)));

  var configuration= builder.Build();