You need MySQL and PostgreSQL up and running.
MySQL should be accepting TCP connections on localhost:3306.
PostgreSQL should be accepting TCP connections on localhost:5432.
Both of them should grant full access to user 'ejabberd_test' with
password 'ejabberd_test' on database 'ejabberd_test'.

Here is a quick setup example:

$ psql template1
template1=# CREATE USER ejabberd_test WITH PASSWORD 'ejabberd_test';
template1=# CREATE DATABASE ejabberd_test;
template1=# GRANT ALL PRIVILEGES ON DATABASE ejabberd_test TO ejabberd_test;

$ mysql
mysql> CREATE USER ejabberd_test IDENTIFIED BY 'ejabberd_test';
mysql> CREATE DATABASE ejabberd_test;
mysql> GRANT ALL ON ejabberd_test.* TO ejabberd_test;