private void AssertAreMetadataEqual(
            TupleList <AttributeMetadata, AttributeMetadata> expectedMdDiff,
            TupleList <AttributeMetadata, AttributeMetadata> actualMdDiff)
        {
            Assert.AreEqual(expectedMdDiff.Count, actualMdDiff.Count);
            for (int i = 0; i < expectedMdDiff.Count; i++)
            {
                AttributeMetadata expectedMd1 = expectedMdDiff[i].item1;
                AttributeMetadata expectedMd2 = expectedMdDiff[i].item2;
                AttributeMetadata actualMd1   = actualMdDiff[i].item1;
                AttributeMetadata actualMd2   = actualMdDiff[i].item2;

                if (expectedMd1 == null)
                {
                    Assert.IsNull(actualMd1);
                }
                else
                {
                    Assert.AreEqual(0, expectedMd1.FullCompareTo(actualMd1));
                }

                if (expectedMd2 == null)
                {
                    Assert.IsNull(actualMd2);
                }
                else
                {
                    Assert.AreEqual(0, expectedMd2.FullCompareTo(actualMd2));
                }
            }
        }