rspec returns "PG::Error: ERROR: relation "table_name" does not exist"

I've run into this in two instances (updated 6/13/2012):

First:

I haven't yet migrated my test database...

rake db:migrate

...which you need to do before both db:test:prepare and db:test:load.

When you invoke rspec it should prepare and load your database for you anyway. You shouldn't have to do that by hand.

Second:

A typo in my migration. I accidentally reversed my table and column names in the parameter list.

A migration on a Rails 3.1 project:

def change  add_column :had_import_errors, :studies, :boolean, :default => false  add_column :import_data_cache, :studies, :textend

...which is wrong, because has_import_errors and import_data_cache are my column names, and they therefore should come second, not first.

The correct migration, with the table name first was:

def change  add_column :studies, :had_import_errors, :boolean, :default => false  add_column :studies, :import_data_cache, :textend

This usually happens when you have rspec running while migrating (usually via guard). A simple solution is to quit guard, do the migration and restart guard.

It typically indicates that there is another open PostgreSql connection. To bubble up the right error try % rake db:test:prepare

Running test prepare showed the following below and when the open connection (PGAdmin in my case) was closed the issue was resolved.

rake aborted!PG::Error: ERROR:  database "xyz_test" is being accessed by other usersDETAIL:  There are 1 other session(s) using the database.: DROP DATABASE IF EXISTS "xyz_test"Tasks: TOP => db:test:load => db:test:purge(See full trace by running task with --trace)