Make a technical debt payment plan – Trish Khoo consulting

this is so so so true !!!

If tests are not automated as a system is created, the regression testing cost increases massively because it must be done manually. Not only this, but when a system is created without tests, the system itself is usually built in a very untestable way which makes it much more difficult to add automated tests later on.

Source: Make a technical debt payment plan – Trish Khoo consulting