Rigorous testing is helpful, but I think it's the wrong approach. The problem here was lack of requirements and/or rigorous design. In the physical engineering disciplines, much effort is done to think about failure modes of designs before they are implemented. In software, for some reason, the lack of pre-implementation design and analysis is endemic. This leads to things like Heartbleed - not language choice, not tools, not lack of static testing.
I would also go as far as saying if you're relying on testing to see if your code is correct (rather than verify your expectations), you're already SOL because testing itself is meaningless if you don't know the things you have to test - which means up-front design and analysis.
That said, tools and such can help mitigate issues associated with lack of design, but the problem is more fundamental than a "coding error."