Add unit tests for customization order

[zvirja]

Add unit tests to ensure the order in which With(), Do() and auto-properties are assigned, so we ensure to not accidentally change that behavior.

[Jaecen]

@zvirja I'm looking in to creating these unit tests, but I'm seeing different behavior than you specified in #1092

The order of the callback invocations is following:

Constructor
Do() callbacks
With callbacks
AutoProperties callbacks

I'm seeing the AutoProperty callbacks being called before the .With() callbacks. Can you elaborate on what the expected order is?

Here's my repro:

[Fact]
public void BuilderStepsRunInCorrectOrder()
{
    // Arrange
    var fixture = new Fixture();
    var expectedSequence = new[]
    {
        BuildStepTest.Step.Constructor,
        BuildStepTest.Step.DoCallback,
        BuildStepTest.Step.PropertyOneWithCallback,
        BuildStepTest.Step.PropertyTwoAutoProperty,
    };

    // Act
    var buildSetTest = fixture.Build<BuildStepTest>()
        .Do(o => o.InvokableMethod())
        .With(o => o.PropertyOne, BuildStepTest.SpecialValue.SpecificInstance)
        .Create();

    // Assert
    Assert.Equal(expectedSequence, BuildStepTest.Sequence);
}

class BuildStepTest
{
    public static readonly List<Step> Sequence = new List<Step>();

    public class SpecialValue
    {
        public static readonly SpecialValue SpecificInstance = new SpecialValue();
    }

    public enum Step
    {
        Constructor,
        DoCallback,
        PropertyOneWithCallback,
        PropertyOneAutoProperty,
        PropertyTwoWithCallback,
        PropertyTwoAutoProperty,
    }

    public SpecialValue PropertyOne
    {
        get => null;

        set
        {
            if (ReferenceEquals(value, SpecialValue.SpecificInstance))
                Sequence.Add(Step.PropertyOneWithCallback);
            else
                Sequence.Add(Step.PropertyOneAutoProperty);
        }
    }

    public SpecialValue PropertyTwo
    {
        get => null;

        set
        {
            if (ReferenceEquals(value, SpecialValue.SpecificInstance))
                Sequence.Add(Step.PropertyTwoWithCallback);
            else
                Sequence.Add(Step.PropertyTwoAutoProperty);
        }
    }

    public BuildStepTest()
    {
        Sequence.Add(Step.Constructor);
    }

    public void InvokableMethod()
    {
        Sequence.Add(Step.DoCallback);
    }
}