InMemoryDb的单元测试的浮动异常

我有单位( XUnit )测试项目 InMemoryDatabase

public class MyTestDbContext : MyDbContext
{
   public static MyTestDbContext CreateTestDbContext()
   {
      var options = new DbContextOptionsBuilder<MyContext>
       .UseInMemoryDatabase(Guid.NewGuid().ToString())
       .ConfigureWarnings(x => x.Ignore(InMemoryEventId.TransactionIgnoredWarning))
       .Options;
       
       var context = new MyTestDbContext(options);
       
       context.EntitySet1.AddRange(...);
       context.EntitySet2.AddRange(...);
       ...
       context.SaveChanges();
       return context();
   }
}

此外,我还有几个单元测试类( [Fact] )例如,它使用此上下文

public class MyTests
{
  protected readonly MyTestDbContext Context;

  protected MyTests()
  {
    Context = MyTestDbContext.CreateTestDbContext();
  }

  [Fact]
  private async Task MyTest()
  {
    // some code with Assert CRUD operations with Context
  }
}

有什么问题。当我第一次运行测试时(例如,在单元测试proj Clean And Rebuild之后),我得到了失败的随机测试,出现了异常:

System.InvalidOperationException
The entity type 'MyEntity1' was not found. Ensure that the entity type has been added to the model.
 ...

但当我第二次运行测试时,所有测试都成功通过。

为什么会发生这种情况?如何修复?