/// <summary>
/// Creates an <see cref="IWebHostBuilder"/> as if the environment variables are set as per <paramref name="environment"/>.
/// The actual system environment variables are ignored. Command line arguments are not supported, as (by design) everything
/// that can be specified on the command line can also be specified via environment variables.
/// This method is primarily used for writing integration tests where a high degree of control is required,
/// for example to simulate the difference between running in a container or not.
/// </summary>
/// <param name="environment">The fake environment variables to use when constructing the host builder.</param>
/// <param name="functionAssembly">The assembly containing the target function. May be null, in which case the calling assembly
/// is used.</param>
/// <returns>A host builder that can be used for integration testing.</returns>
public static IHostBuilder CreateHostBuilder(IReadOnlyDictionary <string, string> environment, Assembly?functionAssembly = null)
{
var variables = ConfigurationVariableProvider.FromDictionary(environment);
var functionEnvironment = FunctionEnvironment.Create(functionAssembly ?? Assembly.GetCallingAssembly(), new string[0], variables);
return(functionEnvironment.CreateHostBuilder());
}
internal static ConfigurationVariableProvider Combine(ConfigurationVariableProvider primary, ConfigurationVariableProvider secondary) => new CombinedVariableProvider(primary, secondary);
internal CombinedVariableProvider(ConfigurationVariableProvider primary, ConfigurationVariableProvider secondary) => (_primary, _secondary) = (primary, secondary);