Quick history
Graduated 6 months ago in Computer Science (with a first), been working for 4 months taking my first job offer as a junior tester / support engineer.
I am 2 months away from my first 6 month review. This review will state if I have passed my probation (which I am expecting to) along with a usual performance review.
The problem
I hate my current job. The role is 65% testing and 35% customer support. The testing is mundane (often manual testing) and I seriously despise customer support. I often feel that I am rotting away, which is seriously worrying to me as I aspire to become a software developer.
Why did I take the job?
Financial reasons, naivety and not realizing what I wanted to do. But I now know that development is what I want to get involved in.
The review
As I said, the review is coming up. I have always given it 100% and my manager/director has always said how happy he is with my work. I have hinted that the development interests me, even proposing to formalize my lunchtime-developed script which has literally saved me and my colleague 5-20mins per day. I also suggested some other possible-useful in-houses software which would be extremely beneficial (and achievable) that I could develop during our quiet periods (which are plenty) - but he flat out refused and ended up giving me a tonne of terrible jobs.
I am at the stage now that I am prepared to walk out if I won't get an opportunity to get showcase what I can really do and get a chance in development. I know the company is actively looking at developers, and a few months ago I did overhear them discussing a junior developer, but he said they needed someone experienced. However, as they have already invested in me, I think I could have a much stronger case at getting the role.
How can I give them and myself the best possible chance to reach an agreement with my manager? I would somehow need to get across (politely) that given the chance I am prepared to study in my own time/do homework etc to learn the technologies but also that I will hand in my notice if they don't offer me a new role as a junior developer - with the promise of development.
Do I even stand a chance?