At my current workplace, we don't have any testers, the rationale for that from the management being: "if we had testers, you wouldn't test your own code at all". This kind of thinking seems to be detrimental to product quality, as while I do test my own code, there are a lot of things that I will miss just for the fact that I know the system inside out and don't know how to use it "wrong". Black box testing doesn't really work as I subconsciously avoid the pitfalls that a dedicated tester would fall into. A lot of my time goes into fixing bugs that have slid into production code and found by the end user.
The system in question is large but is developed solely by me. This has also caused some managemental duties to fall on my lap, such as defining schedules and working on specifications.
Should these kind of tasks be my responsibility? I see myself strictly as a programmer and nothing else. And if these are my responsibility, to what extent? When is a project so large that it requires testers? Should a programmer have to refine the specification, worry about management of the project or even provide customer support?
Some might have got the impression that I am against widening my responsibilities – that is not the case, I'm eager to get a role that involves more management duties, but currently it is not in my job description. Until I'm officially employed as such or the additional duties start showing in my paycheck, I'm going to think of myself as 'just' a programmer. Unfortunately, as a junior developer, shifting to managerial duties is not going to happen very soon.
Excellent answers so far, keep them coming if you have something to add or personal experiences to share!