remove unused paramter.

spec/database_cleaner/active_record/truncation/mysql2_spec.rb

@@ -3,7 +3,7 @@ require 'database_cleaner/active_record/truncation'
 require 'database_cleaner/active_record/truncation/shared_fast_truncation'
 
 RSpec.describe DatabaseCleaner::ActiveRecord::Truncation do
-  let(:helper) { ActiveRecordHelper.new(nil, :mysql2) }
+  let(:helper) { ActiveRecordHelper.new(:mysql2) }
 
   let(:connection) { helper.connection }
 

spec/database_cleaner/active_record/truncation/mysql_spec.rb

@@ -3,7 +3,7 @@ require 'database_cleaner/active_record/truncation'
 require 'database_cleaner/active_record/truncation/shared_fast_truncation'
 
 RSpec.describe DatabaseCleaner::ActiveRecord::Truncation do
-  let(:helper) { ActiveRecordHelper.new(nil, :mysql) }
+  let(:helper) { ActiveRecordHelper.new(:mysql) }
 
   let(:connection) { helper.connection }
 

spec/database_cleaner/active_record/truncation/postgresql_spec.rb

@@ -3,7 +3,7 @@ require 'database_cleaner/active_record/truncation'
 require 'database_cleaner/active_record/truncation/shared_fast_truncation'
 
 RSpec.describe DatabaseCleaner::ActiveRecord::Truncation do
-  let(:helper) { ActiveRecordHelper.new(nil, :postgres) }
+  let(:helper) { ActiveRecordHelper.new(:postgres) }
 
   let(:connection) { helper.connection }
 

spec/database_cleaner/active_record/truncation/sqlite3_spec.rb

@@ -2,7 +2,7 @@ require 'support/active_record/active_record_helper'
 require 'database_cleaner/active_record/truncation'
 
 RSpec.describe DatabaseCleaner::ActiveRecord::Truncation do
-  let(:helper) { ActiveRecordHelper.new(nil, :sqlite3) }
+  let(:helper) { ActiveRecordHelper.new(:sqlite3) }
 
   let(:connection) { helper.connection }
 

spec/database_cleaner/data_mapper/truncation/sqlite3_spec.rb

@@ -2,7 +2,7 @@ require 'support/data_mapper/data_mapper_helper'
 require 'database_cleaner/data_mapper/truncation'
 
 RSpec.describe DatabaseCleaner::DataMapper::Truncation do
-  let(:helper) { DataMapperHelper.new(nil, :sqlite3) }
+  let(:helper) { DataMapperHelper.new(:sqlite3) }
 
   let(:connection) { helper.connection }
 

spec/database_cleaner/sequel/deletion_spec.rb

@@ -9,7 +9,7 @@ module DatabaseCleaner
 
       %w[mysql mysql2 sqlite3 postgres].map(&:to_sym).each do |db|
         context "using a #{db} connection" do
-          let(:helper) { SequelHelper.new(nil, db) }
+          let(:helper) { SequelHelper.new(db) }
 
           around do |example|
             helper.setup

spec/database_cleaner/sequel/truncation_spec.rb

@@ -10,7 +10,7 @@ module DatabaseCleaner
 
       %w[mysql mysql2 sqlite3 postgres].map(&:to_sym).each do |db|
         context "using a #{db} connection" do
-          let(:helper) { SequelHelper.new(nil, db) }
+          let(:helper) { SequelHelper.new(db) }
 
           around do |example|
             helper.setup

spec/support/database_helper.rb

@@ -1,6 +1,6 @@
 require 'yaml'
 
-class DatabaseHelper < Struct.new(:config, :db)
+class DatabaseHelper < Struct.new(:db)
   def setup
     create_db
     establish_connection