Can MySQL Workbench generate data? Is there a way to generate mass rows of dummy data in a table for testing in workbench? 

If not, are there any free tools out there that is able to do that?
You can do this quickly with SQL if the actual data inserted doesn't matter. Create your table and insert one record manually. If the table has a unique/primary key then remove this for the moment.

Then do a insert into table select * from table; This will double the number of records. Do it again to double that (having so 4 records) and so on. Each run will double the (same) records giving you qickly a huge number of them. To make this even faster you can duplicate the query string in the editor. Eg. having 30 insert queries in the editor you can get 2^30 records with a single run of the full editor content.

Once you have enough rows and you want your primary/unique key back run an update over the table, setting the key column to some unique value and then add the primary/unique key back.