In my specific case, that I've mentioned, the tests surely increased the confidence as they were the part of the whole process, where the results from the tests

In my specific case, that I've mentioned, the tests surely increased the confidence as they were the part of the whole process, where the results from the tests were used to modify the product in question until it was able to pass all the tests. The tests allowed to proactively "solve the bugs" which would otherwise produce much more problems if the product had been used in production without these tests.