[sqlite] left outer join returns duplicates

[Philip Riggs]

I have the two following tables for testing:
Test1)  rowid | class | join_value
            1 | 'one' | 1
            2 | 'two' | 2
Test2)  rowid | type | join_value
            1 | 'number' | 1
            2 | 'string' | 2
and peform the following query:
select * from test1 natural join test2
I expect the following:
test1.rowid | test1.class | test1.join_value | test2.type
1 | one | 1 | number
2 | two | 2 | string
but I instead get the following:
test1.rowid | test1.class | test1.join_value | test2.type
1 | one | 1 | number
2 | two | 2 | string
1 | one | 1 | number
2 | two | 2 | string
Why are my data duplicating rows? I've been over the SQL statement in 
books and this is the way it demonstrates this query, but the SQLite 
results don't match what the books say to expect. I even tried this:

select test1.class, test2.type from test1 natural join test2 group by 
class, type

But still get duplicates.