The IsNull test is failing because it is an initialized empty array.

[akshays2112]

GetTrack_TrackIdMarket_AvailableMarketsIsNull test fails because returned response.AvailableMarkets is not null but an empty array.

Suggest something like the following code which I tested out and then the test successfully runs:

Assert.IsNull(response?.AvailableMarkets?.Length == 0 ? null : "Array not empty.");