在子实例设置属性值设置为一个固定值与Autofixture [英] Setting property value on child instance to a fixed value with Autofixture

问题描述

是否有可能建立一个与家长时Autofixture对孩子实例分配一个固定值的属性？这将添加默认值到像一个魅力子实例的所有属性，但我想重写，并分配一个特定的值到子实例的属性之一。

Is it possible to assign a fixed value to a property on a child instance when building a parent with Autofixture? It will add default values to all the properties on the child instance like a charm, but I would like to override and assign a specific value to one of the properties on the child instance.

鉴于这种父/子关系：

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public Address Address { get; set; }
}

public class Address
{
    public string Street { get; set; }
    public int Number { get; set; }
    public string City { get; set; }
    public string PostalCode { get; set; }
}

我想一个特定的值分配给市物业上的地址实例。我想在这个测试代码行：

I would like to assign a specific value to the City property on the address instance. I was thinking in the lines of this test code:

var fixture = new Fixture();

var expectedCity = "foo";

var person = fixture
    .Build<Person>()
    .With(x => x.Address.City, expectedCity)
    .Create();

Assert.AreEqual(expectedCity, person.Address.City);

这是不可能的。我想，通过反射异常

That is not possible. I guess, by the reflection exception

System.Reflection.TargetException : Object does not match target type.

...这Autofixture试图值分配给在Person实例城酒店，而不是一个地址实例。

...that Autofixture tries to assign the value to a City property on the Person instance instead of an Address instance.

有什么建议？

是的，我知道我可以只添加像一个额外的步骤以下内容：

And yes, I know that I could just add an extra step like the following:

var fixture = new Fixture();

var expectedCity = "foo";

// extra step begin
var address = fixture
    .Build<Address>()
    .With(x => x.City, expectedCity)
    .Create();
// extra step end

var person = fixture
    .Build<Person>()
    .With(x => x.Address, address)
    .Create();

Assert.AreEqual(expectedCity, person.Address.City);

...但所期待的第一个版本或类似的东西（更少的步骤，更简洁）。

...but was hoping for the first version or something similar (fewer steps, more terse).

请注意：我使用Autofixture v3.22.0

Note: I'm using Autofixture v3.22.0

推荐答案

为了不被轻视的问题，但最简单的解决方案，实际上可能是这样的：

Not to be dismissive of the question, but the simplest solution might actually be this:

[Fact]
public void SimplestThingThatCouldPossiblyWork()
{
    var fixture = new Fixture();
    var expectedCity = "foo";
    var person = fixture.Create<Person>();
    person.Address.City = expectedCity;
    Assert.Equal(expectedCity, person.Address.City);
}

分配到物业是大多数语言已经处于（C＃擅长肯定一样），所以我不认为AutoFixture需要一个复杂的DSL重现该功能一半。

Assignment of explicit values to properties is something most languages already excel at (C# certainly does), so I don't think AutoFixture needs a complicated DSL to reproduce half of that functionality.

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