Can you test apps on a google locked phone?
No... Assuming by "Google Locked" you mean it has an enforced Factory Reset Protection which requires the previous owner's (or last active) Google account credentials. When this is active you cannot get to the launcher or perform any actions on the device until it is "unlocked" using the proper Google credentials. It is "locked", is essentially a non-functional device, and you cannot get past the Google Credentials screen in any way. 

Some further information that might be applicable in our FRP base question, How to bypass “Verify your account” (Factory Reset Protection)