Dunkin Donuts revived some of their failing stores with an SMS campaign that they advertised through online ads and radio. The campaign rewarded customers for sharing the text offers with their friends. By encouraging sharing and word-of-mouth in their promotion, they leveraged their spending on their SMS campaign and managed to provide sufficient incentive that 17% of those who received texts forwarded them and 7,500 people opted in to their loyalty program. The result was a 21% increase in store traffic. Impressive results.

Similar to email, SMS has anti-spam laws which differ from country to country. As a general rule, it’s important to obtain the recipient’s permission before sending any text message, especially an SMS marketing type of message. Permission can be obtained in a myriad of ways, including allowing prospects or customers to: tick a permission checkbox on a website, filling in a form, or getting a verbal agreement.[16]
Once you have done the analysis, determined your goal and formulated your hypothesis, it’s time to set up your test. The best way is to do an A/B test. An A/B test compares version A (the original version) to changes made in a version B while all other conditions are kept the same. If you send the test to a big enough group of recipients and all conditions (e.g. time of day, day in the week, type of audience etc.) are kept the same, an A/B test will let you conclude whether the results can be attributed to the made changes or whether they happened due to chance. 
This question exists for many. First, NEVER EVER purchase a list of mobile numbers. (SMS/MMS) marketing is permission based, and ultimately you want a list of customers numbers who are genuinely interested in your product or service and are happy to receive your text message and are likely to buy your goods and service. Remember, you can turn customers off and possibly upset a lot of your potential customers when sending text messages on their mobile devices without their consent.