AutoFixture是否有一种机制来检查返回任何类型的列表的方法永远不会返回null？

Question

我想编写一个测试,检查给定命名空间中的类.如果它们返回null,则必须检查返回任何类型列表的类的所有方法.如果是这样,测试必须失败.

类/方法本身也有自动锁定的依赖项(构造函数参数和方法参数).

AutoFixture有一种机制来检查返回任何类型列表的方法永远不会返回null吗？

示例类:

public class UserService
{
    private readonly IRemotingFacade _remotingFacade;

    public UserService(IRemotingFacade remotingFacade)
    {
        _remotingFacade = remotingFacade;
    }

    // directly return a list
    public IEnumerable<User> GetUsers()
    {

    }

    // directly return a list, pass method parameters
    public IEnumerable<User> GetUsers(string filter)
    {

    }

    // wrapped list
    public IBusinessResponse<IEnumerable<User>> GetUsers()
    {

    }


    // wrapped list, pass method parameters
    public IBusinessResponse<IEnumerable<User>> GetUsers(string filter)
    {

    }
}

所以请说明列表可以包含在另一个对象中.

Answer 1

Ruben Bartelink上面的评论是正确的.令人惊讶的是,AutoFixture.Idioms还没有(还)有那个特定的测试,尽管引入该库的第一个惯用测试是它在命令端的等效测试:GuardClauseAssertion

但是,我认为这是一个很好的主意(我不知道为什么我之前没想过),所以我现在在积压中添加了一个新任务.

Answer 2

AutoFixture 3.18.0引入了一个名为Idioms.FsCheck的新胶水库,它使用FsCheck实现一个名为的可重用断言ReturnValueMustNotBeNullAssertion.

此新断言验证(或至少可能使得返回值(Query)的方法不返回null.

安装

Idioms.FsCheck在NuGet上可用:

PM> Install-Package AutoFixture.Idioms.FsCheck

方案

的UserService使用的一个实例注入IRemotingFacade和公开两个^[1]查询:

• 用户[] GetUsers()
• 用户[] GetUsers(int)

场景#1:注入的实例IRemotingFacade返回null:

[Theory, UnitTestConventions]
public void Scenario1(
    ISpecimenBuilder builder,
    [Frozen]Mock<IRemotingFacade> stub)
{
    stub.Setup(x => x.GetUsers()).Returns((User[])null);

    var sut = from x in new Methods<UserService>() select x.GetUsers();

    var assertion = new ReturnValueMustNotBeNullAssertion(builder);
    Assert.Throws<ReturnValueMustNotBeNullException>(() =>
        assertion.Verify(sut));
}

场景#2:注入的an实例IRemotingFacade不返回null:

[Theory, UnitTestConventions]
public void Scenario2(
    ISpecimenBuilder builder,
    [Frozen]Mock<IRemotingFacade> stub,
    User[] users)
{
    stub.Setup(x => x.GetUsers()).Returns(users);

    var sut = from x in new Methods<UserService>() select x.GetUsers();

    var assertion = new ReturnValueMustNotBeNullAssertion(builder);
    Assert.DoesNotThrow(() => assertion.Verify(sut));
}

场景3:如果i为-1则 GetUsers(int)返回null:

[Theory, UnitTestConventions]
public void Scenario3(
    ISpecimenBuilder builder,
    [Frozen]Mock<IRemotingFacade> stub,
    User[] users)
{
    stub.Setup(x => x.GetUsers()).Returns(users);

    var sut = from x in new Methods<UserService>() 
              select x.GetUsers(default(int));

    var assertion = new ReturnValueMustNotBeNullAssertion(builder);
    Assert.Throws<ReturnValueMustNotBeNullException>(
        () => assertion.Verify(sut));
}

备注

如果您只安装了F#3.1,则还可以在app.config文件中添加程序集绑定重定向:

<dependentAssembly>
  <assemblyIdentity name="FSharp.Core" 
                    publicKeyToken="b03f5f7f11d50a3a" 
                    culture="neutral" />
  <bindingRedirect oldVersion="0.0.0.0-4.3.1.0" 
                   newVersion="4.3.1.0" />
</dependentAssembly>

的UnitTestConventionsAttribute定义为:

internal class UnitTestConventionsAttribute : AutoDataAttribute
{
    internal UnitTestConventionsAttribute()
        : base(new Fixture().Customize(new AutoMoqCustomization()))
    {
    }
}

使用Albedo执行反射查询.

^[1]对于演示,我简化了原始代码,如下所示:

public class User
{
}

public interface IRemotingFacade
{
    User[] GetUsers();
}

public class UserService
{
    private readonly IRemotingFacade remotingFacade;

    public UserService(IRemotingFacade remotingFacade)
    {
        if (remotingFacade == null)
            throw new ArgumentNullException("remotingFacade");

        this.remotingFacade = remotingFacade;
    }

    public User[] GetUsers()
    {
        return this.remotingFacade.GetUsers();
    }

    public User[] GetUsers(int i)
    {
        if (i == -1)
            return null;

        return this.remotingFacade.GetUsers();
    }
}