I have been a sole trader from Russia when I got a contract with a Czech IT company. I work on its co-projects with English companies as a back-end tester on an e-commerce product.
There was an exciting project for virtual reality — a classic successful start-up — where I independently led separate subprojects, tested a lot and wrote codes. Apart from the plain ones that QA engineers write to simplify their work, I worked on the ones that developers usually write — integration and unit tests.
They did not have time and, thereby, I helped them. It is the way I overcame my fear of “getting into the main product code”. Now, working on the current project, I powerfully use white-box testing. I serve the developers’ requests and give recommendations on test coverage. If I need the main product code editing to implement autotests smoothly and beautifully, I do it myself.
Needless to say that these edits go into the code right after the developers’ checking and approval. 🙂