SELECT * FROM a WHERE id IN (sub query) . When sub query is incorrect . return all rows of table a

When I have 2 tables like this 
create table test
(
id                int4,
shapeid        int4
);

table testb
(
id                 int4
);

table test has 4 records and table has 1 recors.

sql  " select shapeid from testb; "     Failed.                                                    

but  sql  " select * from test where shapeid in ( SELECT shapeid FROM testb ); "  return all records of table test                

sql like this delete all records of my talbe !