That said, Antithesis doesn't require you to write manual tests, integration or otherwise. It requires your software system to be packaged in containers, which is fairly straightforward, and then requires a workload to be written which will emulate the normal functioning of the software system. So for example an e-commerce store would have product views, cart adds, checkouts, etc.
With this, Antithesis can start testing (running your workload, varying inputs, injecting faults, etc) the software and looking for violations of test properties. There are many (60+) test properties that come "out of the box" such as crashes, out of memory, etc. You can (and should) also define custom properties that are unique to your system, as this will surface more problems.
As your tests run, violations of test properties are reported, with lots of useful debug information included. Test runs that are particularly interesting can have a lot of extra analysis done, due to our ability to "rewind" and change inputs, get artifacts, add logging, etc.