There are several counties that have the new emission testing requirements. Harris County (Houston), several counties in the Dallas area, and one county near El Paso.
Any car registered in Harris County can only be tested in Harris County or any other county where the new testing requirements are in place. Therefore, it would be illegal to have a Harris County registered car tested in Fort Bend, Waller, or other neighboring counties. However, next year at this time, some of the surrounding counties of Harris will then be required to use the new emissions testing, unless this piece of (deleted) law is revoked.
My recommendation, start planning NOW to have your vechile tested, count on taking a day vacation from work, and let's get this piece of (deleted) revoked.