Do NOT use your main account for testing various scenarios. You cannot save and then change information - it will just write over your saved information. The best practice is to create separate online accounts for testing. You can use the same email address to keep them all under one umbrella, but make different usernames. You can add something like test after it.
Also, if you think you might want to do a lot of experimenting or testing, you may want to look into using the desktop program this year. With that program, you can create as many test returns as you wish by simply creating new files. If you are married, it also contains a worksheet for comparing married filing jointly vs separately. You can view information about the desktop (CD/Download) program below.
https://turbotax.intuit.com/personal-taxes/cd-download/deluxe.jsp