1 files changed, 79 insertions, 0 deletions
diff --git a/activerecord/test/cases/arel/visitors/mysql_test.rb b/activerecord/test/cases/arel/visitors/mysql_test.rb
new file mode 100644
index 0000000000..f9b468b1d2
--- /dev/null
+++ b/activerecord/test/cases/arel/visitors/mysql_test.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Visitors
+    class MysqlTest < Arel::Spec
+      before do
+        @visitor = MySQL.new Table.engine.connection
+      end
+
+      def compile node
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      it 'squashes parenthesis on multiple unions' do
+        subnode = Nodes::Union.new Arel.sql('left'), Arel.sql('right')
+        node    = Nodes::Union.new subnode, Arel.sql('topright')
+        assert_equal 1, compile(node).scan('(').length
+
+        subnode = Nodes::Union.new Arel.sql('left'), Arel.sql('right')
+        node    = Nodes::Union.new Arel.sql('topleft'), subnode
+        assert_equal 1, compile(node).scan('(').length
+      end
+
+      ###
+      # :'(
+      # http://dev.mysql.com/doc/refman/5.0/en/select.html#id3482214
+      it 'defaults limit to 18446744073709551615' do
+        stmt = Nodes::SelectStatement.new
+        stmt.offset = Nodes::Offset.new(1)
+        sql = compile(stmt)
+        sql.must_be_like "SELECT FROM DUAL LIMIT 18446744073709551615 OFFSET 1"
+      end
+
+      it "should escape LIMIT" do
+        sc = Arel::Nodes::UpdateStatement.new
+        sc.relation = Table.new(:users)
+        sc.limit = Nodes::Limit.new(Nodes.build_quoted("omg"))
+        assert_equal("UPDATE \"users\" LIMIT 'omg'", compile(sc))
+      end
+
+      it 'uses DUAL for empty from' do
+        stmt = Nodes::SelectStatement.new
+        sql = compile(stmt)
+        sql.must_be_like "SELECT FROM DUAL"
+      end
+
+      describe 'locking' do
+        it 'defaults to FOR UPDATE when locking' do
+          node = Nodes::Lock.new(Arel.sql('FOR UPDATE'))
+          compile(node).must_be_like "FOR UPDATE"
+        end
+
+        it 'allows a custom string to be used as a lock' do
+          node = Nodes::Lock.new(Arel.sql('LOCK IN SHARE MODE'))
+          compile(node).must_be_like "LOCK IN SHARE MODE"
+        end
+      end
+
+      describe "concat" do
+        it "concats columns" do
+          @table = Table.new(:users)
+          query = @table[:name].concat(@table[:name])
+          compile(query).must_be_like %{
+            CONCAT("users"."name", "users"."name")
+          }
+        end
+
+        it "concats a string" do
+          @table = Table.new(:users)
+          query = @table[:name].concat(Nodes.build_quoted('abc'))
+          compile(query).must_be_like %{
+            CONCAT("users"."name", 'abc')
+          }
+        end
+      end
+    end
+  end
+end