Blobs

FakeDb allows to get and set a blob stream.

[Fact]
public void HowToSetAndGetBlobStream()
{
  // arrange
  var stream = new System.IO.MemoryStream();

  using (Sitecore.FakeDb.Db db = new Sitecore.FakeDb.Db
    {
      new Sitecore.FakeDb.DbItem("home")
        {
          new Sitecore.FakeDb.DbField("field")
        }
    })
  {
    Sitecore.Data.Items.Item item = db.GetItem("/sitecore/content/home");
    Sitecore.Data.Fields.Field field = item.Fields["field"];

    using (new Sitecore.Data.Items.EditContext(item))
    {
      // act
      field.SetBlobStream(stream);
    }

    // assert
    Xunit.Assert.Same(stream, field.GetBlobStream());
  }
}

Important:

Property HasBlobStream is not supported and always returns False.