Automated testing of legacy code: methods of safe refactoring

It is known, that the consequences of an error in production are extremely expensive: they lead to both financial and reputational costs. In this case, it must be taken into account that the search and correction of the causes must be carried out as carefully as possible. This is connected with the fact that, as practice statistics shows, correcting one mistake, in the absence of a competently built testing process, can lead to the introduction of the new ones.

What should the developers who value the quality and reliability of the product do in the situation when in a short time it is required to make changes in the legacy code for which there are no tests?

We will look at the basic approaches to refactoring in order to cover the legacy code with automated tests, and also consider their interaction. You will learn how to choose solutions that allow you to make reliable changes by creating a "reliability grid" around the modifiable module.

The talk will mostly demonstrate examples from the C++ world, yet it will also be relevant for other programming languages.