Mocking dataframe for testing in python

I am trying to mock a dataframe for unit testing in python. here is the form of the table:

However, I am having trouble hard coding a dataframe to have a json within it. This is my attempt at mocking a record:

        test_strip = pd.DataFrame(
        [[1],
         "2020-09-21",
         [{'WTI': {'1604188800000': '40.25',
                 '1606780800000': '40.51',
                 '1609459200000': '40.81',
                 '1612137600000': '41.13',
                 '1614556800000': '41.45',
                 '1617235200000': '41.74',
                 '1619827200000': '42.00',
                 '1622505600000': '42.22'}
         }],
         [1]],
        columns=['id','trade_date','prices','contract']
    )

This yields the following error:

ValueError: 4 columns passed, passed data had 10 columns

So it appears it is interpreting my json as separate records. Appreciate any help anyone might have.