My initial instinct is that the Test Engineer job would position you better for an MBA. Here's why: you are engaging with end users, understanding their needs (in business, this would translate to 'customer needs analysis'), you would have to develop very strong communication skills with the customers (who are presumably business people), you would gain a stronger understanding of your customers' world (banking, etc.), and you would have more of project and people management/oversight responsibility that again would sharpen your communication and leadership skills. The software engineer role sounds like a strictly technical role in which it would be difficult to develop these other skill sets.
This is just my opinion, but I hope it is helpful to you. I would also consider what the career paths are from each of those roles within your company. As a Test Engineer, where could you go? What is involved in the next level of that position? More management/business side work? Could you ultimately transition to a business role on that path? What about for the software engineer role -- if you progress in that position, where does it lead you? You want to get on a path that will ultimately give you the best chance of positioning yourself as a business person and that enables you to develop leadership skills and experiences.
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