Keep applying to positions you find. And even within your own company, show that you're interested in becoming a developer. While you're a tester, you can write applications to automate tests. At the very least, it could get you a pay raise because you show initiative and are increasing productivity. It gets you experience and that's what companies are looking for.
Also another big thing in any industry is who you know. Join communities and forums like this one, or join a couple open source projects. That way you get to know other developers so if their company has a job opening they can put a word in for you. In the case of open source projects you also get something else you can put in your portfolio and resume.
Another option is to look for a part time internship at a company. You wouldn't be paid for your work but if you show your are eager to learn and work hard, they just might hire you on. If they don't hire you, you still get another thing to put in your resume/work experience. When you are just starting out sometimes it is best to take on free work/projects just to build up that work experience.