Why does software need automated tests?

The Problem Without Tests

Software consists of many interconnected parts. A change at one location can destroy something at a completely different location. Without tests, this either becomes apparent during manual testing – which takes time – or in production.

Over time, this creates a system that no one wants to change anymore. This is more expensive than any testing effort.

What Tests Cost and Bring

Automated tests significantly increase the effort during development. They reduce the effort for every subsequent change – and software is changed much more frequently during its lifetime than it is built.

For an application intended to run for two years, this usually pays off.

What Should Be Tested

Not everything. A selection is sensible:

• The processes used daily
• Everything related to money or deadlines
• Rights and access restrictions
• Every error that has occurred once – to ensure it does not recur

What You Will Notice

Nothing directly. Indirectly: Changes happen faster, errors in existing functions become rarer, and switching service providers becomes possible because the new person can verify whether they have broken something.

That is why the question about tests is also a question about your independence.