Challenges of Automated System Testing

Automated unit testing relies on predicting outputs in advance, but system outputs may be large or unpredictable

Explanation

Automated system testing is harder because automated unit testing relies on predicting test outputs and encoding predictions in the test program. However, the point of implementing a system may be to generate outputs that are large or cannot be easily predicted in advance. A tester may be able to examine an output and check its credibility without necessarily being able to create it in advance.