Function.cs

// Copyright 2020, Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

using Google.Cloud.Functions.Framework;
using Google.Cloud.Functions.Hosting;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using System.Threading.Tasks;

namespace Google.Cloud.Functions.Examples.TestableDependencies;

// The dependency interface required by the function.
public interface IDependency
{
    public string Name { get; }
}

// The production dependency, configured in the Startup class.
public class ProductionDependency : IDependency
{
    public string Name => "Production dependency. Don't use me in tests!";
}

/// <summary>
/// Adds the production dependency to the service collection.
/// </summary>
public class Startup : FunctionsStartup
{
    public override void ConfigureServices(WebHostBuilderContext context, IServiceCollection services) =>
        services.AddSingleton<IDependency, ProductionDependency>();
}

[FunctionsStartup(typeof(Startup))]
public class Function : IHttpFunction
{
    private readonly IDependency _dependency;

    public Function(IDependency dependency) =>
        _dependency = dependency;

    public async Task HandleAsync(HttpContext context)
    {
        await context.Response.WriteAsync(
            $"Dependency configured for function: {_dependency.Name}",
            context.RequestAborted);
    }
}