How does Google test and check Android apps uploaded to Play Store?
As per my personal experience, Google does not check each and every functionality of the app, it just does some routine validation check for publication. Whereas Apple's App Store does the opposite, Apple requires working login credentials for checking each and every screen at least.
Now, it is perfectly fine to publish an app in Play Store, which does nothing, i.e., useless till the time it is adhering to the Play Store's policy. Now if you found some apps which are violating the listed policy Play Store Policy, you can always report it to Google and most probably Google will unlist that app for sure.