Create a in-memory json configuraiton that is used to mock IConfiguration.

BuildInMemoryConfiguration.cs

var inMemorySettings = new Dictionary<string, string> 
{
    {"Languages:0", "en"},
    {"Languages:1", "cn"},
    {"Languages:2", "ar"}
    {"SectionName:SomeKey", "SectionValue"},
    //...populate as needed for the test
};

var configuration = new ConfigurationBuilder()
                .AddInMemoryCollection(inMemorySettings)
                .Build();
                
/*
references:
https://stackoverflow.com/questions/64794219/how-to-mock-iconfiguration-getvalue
https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-6.0&viewFallbackFrom=aspnetcore-3.0#memory-configuration-provider
*/