Just had a seemingly odd Rails test error:
Loaded suite /usr/lib/ruby/gems/1.8/gems/rake-0.7.3/lib/rake/rake_test_loader
Started
E/usr/lib/ruby/1.8/sqlite3/errors.rb:94:in `check': SQL logic error or missing database (SQLite3::SQLException)
Simple enough to fix- it turns out my primary key (the "id" column) in the test fixtures weren't unique.
If you get this error, check your fixtures!