server/test/Core.Test/AutoFixture/SutProvider.cs

using System;
using System.Collections.Generic;
using AutoFixture;
using AutoFixture.Kernel;
using System.Reflection;
using System.Linq;

namespace Bit.Core.Test.AutoFixture
{
    public class SutProvider<TSut> : ISutProvider
    {
        private Dictionary<Type, Dictionary<string, object>> _dependencies;
        private readonly IFixture _fixture;
        private readonly ConstructorParameterRelay<TSut> _constructorParameterRelay;

        public TSut Sut { get; private set; }
        public Type SutType => typeof(TSut);

        public SutProvider() : this(new Fixture()) { }

        public SutProvider(IFixture fixture)
        {
            _dependencies = new Dictionary<Type, Dictionary<string, object>>();
            _fixture = (fixture ?? new Fixture()).WithAutoNSubstitutions().Customize(new GlobalSettings());
            _constructorParameterRelay = new ConstructorParameterRelay<TSut>(this, _fixture);
            _fixture.Customizations.Add(_constructorParameterRelay);
        }

        public SutProvider<TSut> SetDependency<T>(T dependency, string parameterName = "")
            => SetDependency(typeof(T), dependency, parameterName);
        public SutProvider<TSut> SetDependency(Type dependencyType, object dependency, string parameterName = "")
        {
            if (_dependencies.ContainsKey(dependencyType))
            {
                _dependencies[dependencyType][parameterName] = dependency;
            }
            else
            {
                _dependencies[dependencyType] = new Dictionary<string, object> { { parameterName, dependency } };
            }

            return this;
        }

        public T GetDependency<T>(string parameterName = "") => (T)GetDependency(typeof(T), parameterName);
        public object GetDependency(Type dependencyType, string parameterName = "")
        {
            if (DependencyIsSet(dependencyType, parameterName))
            {
                return _dependencies[dependencyType][parameterName];
            }
            else if (_dependencies.ContainsKey(dependencyType))
            {
                var knownDependencies = _dependencies[dependencyType];
                if (knownDependencies.Values.Count == 1)
                {
                    return _dependencies[dependencyType].Values.Single();
                }
                else
                {
                    throw new ArgumentException(string.Concat($"Dependency of type {dependencyType.Name} and name ",
                        $"{parameterName} does not exist. Available dependency names are: ",
                        string.Join(", ", knownDependencies.Keys)));
                }
            }
            else
            {
                throw new ArgumentException($"Dependency of type {dependencyType.Name} and name {parameterName} has not been set.");
            }
        }

        public void Reset()
        {
            _dependencies = new Dictionary<Type, Dictionary<string, object>>();
            Sut = default;
        }

        ISutProvider ISutProvider.Create() => Create();
        public SutProvider<TSut> Create()
        {
            Sut = _fixture.Create<TSut>();
            return this;
        }

        private bool DependencyIsSet(Type dependencyType, string parameterName = "")
            => _dependencies.ContainsKey(dependencyType) && _dependencies[dependencyType].ContainsKey(parameterName);

        private object GetDefault(Type type) => type.IsValueType ? Activator.CreateInstance(type) : null;

        private class ConstructorParameterRelay<T> : ISpecimenBuilder
        {
            private readonly SutProvider<T> _sutProvider;
            private readonly IFixture _fixture;

            public ConstructorParameterRelay(SutProvider<T> sutProvider, IFixture fixture)
            {
                _sutProvider = sutProvider;
                _fixture = fixture;
            }

            public object Create(object request, ISpecimenContext context)
            {
                if (context == null)
                {
                    throw new ArgumentNullException(nameof(context));
                }
                if (!(request is ParameterInfo parameterInfo))
                {
                    return new NoSpecimen();
                }
                if (parameterInfo.Member.DeclaringType != typeof(T) ||
                    parameterInfo.Member.MemberType != MemberTypes.Constructor)
                {
                    return new NoSpecimen();
                }

                if (_sutProvider.DependencyIsSet(parameterInfo.ParameterType, parameterInfo.Name))
                {
                    return _sutProvider.GetDependency(parameterInfo.ParameterType, parameterInfo.Name);
                }


                // This is the equivalent of _fixture.Create<parameterInfo.ParameterType>, but no overload for
                // Create(Type type) exists.
                var dependency = new SpecimenContext(_fixture).Resolve(new SeededRequest(parameterInfo.ParameterType,
                    _sutProvider.GetDefault(parameterInfo.ParameterType)));
                _sutProvider.SetDependency(parameterInfo.ParameterType, dependency, parameterInfo.Name);
                return dependency;
            }
        }
    }
}