From the details of your question I assume that the contribution for 2018 was made to your own HSA, not to your spouse's HSA. If that assumption is correct, yes, if you yourself remain an HSA-eligible individual through December 31, 2019, you will have completed the testing period for your use of the last-month rule in 2018.
It doesn't matter whose name the insurance policy is in as long as you are covered.
