在Xunit测试中创建System.Windows.Media.Pen时出现间歇性错误

Question

我有很多Xunit测试都可以正常工作，但是有时调用下面列出的代码会失败。尽管这些测试不一定共享相同的受影响的代码，但它们却一起失败。如果我再次运行它们，它们很可能全部通过，并且在几次测试运行中也不会再看到错误。

所有测试均失败，并显示类似以下内容：

Message: 
    System.IndexOutOfRangeException : Index was outside the bounds of the array.
  Stack Trace: 
    ArrayItemList`1.EntryAt(Int32 index)
    FrugalObjectList`1.get_Item(Int32 index)
    Freezable.AddContextToList(DependencyObject context, DependencyProperty property)
    Freezable.AddContextInformation(DependencyObject context, DependencyProperty property)
    Freezable.AddInheritanceContext(DependencyObject context, DependencyProperty property)
    DependencyObject.ProvideSelfAsInheritanceContext(DependencyObject doValue, DependencyProperty dp)
    DependencyObject.ProvideSelfAsInheritanceContext(Object value, DependencyProperty dp)
    DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
    DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType, Boolean isInternal)
    DependencyObject.SetValueInternal(DependencyProperty dp, Object value)
    Pen.ctor(Brush brush, Double thickness)
    CanvasPathDrawer.CreateOutlinePen() line 194

失败的代码是

private Pen CreateOutlinePen()
{
    var outlinePenBrush = CreateOutlinePenBrush(OutlineType.None);

    var outlinePen = new Pen(outlinePenBrush, 1) // Fails on this line
    {
        EndLineCap = PenLineCap.Round,
        DashCap = PenLineCap.Round,
        LineJoin = PenLineJoin.Round,
        StartLineCap = PenLineCap.Round,
        MiterLimit = 10.0
    };

    return outlinePen;
}

private static Brush CreateOutlinePenBrush(OutlineType outlineType)
{
    switch (outlineType)
    {
        case OutlineType.None:
            return OutlineTypeNoneBrush;
        // etc
    }
}

public static Brush OutlineTypeNoneBrush { get; } = new SolidColorBrush(Colors.Transparent);

使用[StaFact]属性在STA线程上运行测试。

我想我已经错过了有关如何创建对象的基本知识。我是否应该每次都创建一个新画笔？