- Custom software is tested in three ways: automated tests written by the vendor, tests on the connections to other systems, and tests by the people who will use it every day.
- Tests matter on the difficult cases: missing data, duplicates, failed requests, users without permissions.
- Before handover the vendor should show the list of tests run and their results.
- Acceptance is closed in writing: what was tested, by whom, and which defects remain to be fixed by what date.
All frequently asked questions →
Three kinds of test
You need all three. Each finds errors the others miss.
- Automated tests: small programs that check every function at every change. The vendor writes them and they stay in the delivered code.
- Integration tests: what happens when the CRM does not respond, when the ERP rejects a record, when an email bounces.
- User tests: two or three people from the department use the software on everyday work and report what does not add up.
What to push on
The customer with two addresses, the file with an extra column, the order cancelled halfway. Ask the vendor to run them in front of you.
If the software uses AI, you also need tests on the answers: a list of real questions with the right answer next to each, rerun at every change. That is how you notice when an update makes answers worse.
Handover and acceptance
Before signing acceptance, ask for three things: the list of tests, access to the automated tests in the repository, and open defects each with a date.
At Yempik the first version is tested with the people who will use the system before the project is extended, and at handover we document how it works and how it connects.
More questions
Who should test, the vendor or the company?
Both. The vendor runs automated and technical tests; the company tries the software on everyday work, because only users know which cases really happen.
How much time should we set aside for testing?
Automated tests grow with the software and cost the company no time. For user tests, one or two weeks on real work usually brings out the cases that matter.
Answer edited by Raffaele Zarrelli, co-founder of Yempik, written with Claude. Prices, timelines and cases are the ones Yempik publishes; this page was last updated on 8 November 2026.
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