How can we minimize bugs Through software testing ??

This problem often occurs recently. When a function is clearly completed, a bug occurs during the overall test, and a process is clearly a test, there are still many blind spots from products to customers that have not been tested. Maybe there will be fewer companies in the testing team, which is unknown. In my opinion, small companies still cannot afford the consumption of the testing team. If there is no testing team, what should I do if I only test functions developed by developers ??, Maybe it is time to use unit testing. Or, in this way, when there are only a few people in the project, you can first have a person to test, others to modify, then change to another person to test, and others to modify, will it be better ?? I have been wondering about this!

Also, in many cases, a single function is completed and the test is okay. However, another function is developed later. When the function method is reused, or after modification, as a result, some logic bugs exist in the original functions. What should I do? According to the recent test summary, many of these problems occur in many cases, the Code has been modified several times to gradually get rid of the intention to create the method. Although the method function is powerful, there are often many dead corners of thinking. Although this can be found in the overall test, however, there will still be the first paragraph that says, a process, testing is okay, and there is still a bug on the client side. it is unknown whether our development is too inertial or people have to be lazy. However, it is not practical to rely on tests like this, because in the case of insufficient incidents, the bug continues, and the code will become chaotic with later modifications. After all, you may not be able to understand the ideas you developed at that time.

How can we minimize bugs? What should we do in order to make code highly reusable and minimize the bug of dead-end thinking? Will these methods be suitable for small development teams? In such an emergency, is there any better way to solve this problem? Please give me some advice. Thank you! Thank you!

How can we minimize bugs Through software testing ??