When to test - longer cycle

So I had my period Feb 12th. Cycles have been getting longer these last few months but still had flashing smiley for 3 days then solid smiley CD 13. That makes today CD 26. Preg test this morning was negative but holding our hope I could be testing too early? <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Period app</a> days AF not due until March 21st based on cycles being 35-40 days since October. When would you test? Holding out a bit of hope.