When I attempt to run \"rake test\" on a local postgres database, it throws the above exception.
Here is my pg_hba.conf file: # Database administrative login by
localhost as a host refers to a TCP connection, which means the auth method is md5 (password required) per your pg_hba.conf:
# IPv4 local connections: host all all 127.0.0.1/32 md5 # IPv6 local connections: host all all ::1/128 md5
For the peer method to be taken, you'd need to connect through Unix domain sockets, and since you seem to be using a debian-like OS, that means putting /var/run/postgresql in the host field, or nothing at all (it's the default unless environment variables say otherwise).
EDIT: if using database URIs (supported since Rails-4.1, as announced in http://weblog.rubyonrails.org/2014/4/8/Rails-4-1/), the syntax could be:
for localhost:
test: "postgresql://localhost/myapp_test"
for the default Unix socket domain (host field left empty):
test: "postgresql:///myapp_test"