Tried a few strategies, but this seems to be the fastest:
DatabaseCleaner truncate_all: 0.8s
This: 0.2s
# fast truncation of all tables that need truncations (select is 10x faster then truncate)
# https://grosser.it/2012/07/03/rubyactiverecord-fastest-way-to-truncate-test-database/
def truncate_all_tables
config = ActiveRecord::Base.configurations[::Rails.env]
connection = ActiveRecord::Base.connection
connection.disable_referential_integrity do
connection.tables.each do |table_name|
next if connection.select_value("SELECT count(*) FROM #{table_name}") == 0
case config["adapter"]
when "mysql", "mysql2", "postgresql"
connection.execute("TRUNCATE #{table_name}")
when "sqlite", "sqlite3"
connection.execute("DELETE FROM #{table_name}")
connection.execute("DELETE FROM sqlite_sequence where name='#{table_name}'")
end
end
connection.execute("VACUUM") if config["adapter"] == "sqlite3"
end
end
Michael Grosser, the Blog 
This does not work with SQLite:
`SQLite3::SQLException: near “TRUNCATE”: syntax error`
This should fix it:
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gistfile1.rb
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Thanks, much more universal 🙂