incubator-test is not compatible with version 5.*

[alex-childish]

phalcon/incubator-test v1.0.0-alpha.1 is not compatible with Phalcon > v4
I think it's worth mentioning in https://docs.phalcon.io/5.8/unit-testing/#phalcon-incubator-test
There's also a fork that can probably be used instead: https://github.com/KirDE/incubator-test