Discovered something doing a unit test today

SObject class method isClone() does not return true unless the clone source SObject exists in the database.

Account a = new Account(name = '00clonesrc');
insert a;
Account aClone = a.clone(false,true,false,false);
system.debug(LoggingLevel.Info,'isClone='+aClone.isClone());

The debug line shows as: isClone=true

but, don’t do the insert as in this example:

Account a = new Account(name = '00clonesrc');
Account aClone = a.clone(false,true,false,false);
system.debug(LoggingLevel.Info,'isClone='+aClone.isClone());

The debug line shows as: isClone=false

Normally, this might not be an issue but I was unit testing a service layer method and passing cloned sobjects in as arguments without doing the database operation in order to make the tests run faster. This is one place where the DML is required in order to get isClone() to work as expected.

Update 2016-10-04

Per suggestion by Adrian Larson, I retried using a dummy ID

Account a = new Account(id = '001000000000000000', name = '00clonesrc');
Account aClone = a.clone(false,true,false,false);
system.debug(LoggingLevel.Info,'isClone='+aClone.isClone());

The debug line shows as: isClone=true