fix test failures

The tests actually began to fail at
44d71de23fb91601f5cdb40751790eb5900d5911. We added a "title string must
be at least 10 characters" rule to app/models/product.rb, which
prevented 'Foo Bar' from being accepted as an updated title.

Actually, the test framework is somewhat broken because the :one fixture
in test/fixtures/products.yml is broken ("MyString" also does not pass
the >= 10 characters test), and yet, we are able to use it as `@product
= products(:one)` here. Oh well.