`change_table` supports `citext`. Follow up to #12523.

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -355,6 +355,10 @@ def uuid(name, options = {})
         def json(name, options = {})
           column(name, 'json', options)
         end
+
+        def citext(name, options = {})
+          column(name, 'citext', options)
+        end
       end
 
       class TableDefinition < ActiveRecord::ConnectionAdapters::TableDefinition

activerecord/test/cases/adapters/postgresql/citext_test.rb

@@ -19,10 +19,8 @@ def setup
 
     @connection.reconnect!
 
-    @connection.transaction do
-      @connection.create_table('citexts') do |t|
-        t.citext 'cival'
-      end
+    @connection.create_table('citexts') do |t|
+      t.citext 'cival'
     end
     @column = Citext.columns_hash['cival']
   end
@@ -44,15 +42,36 @@ def test_column_sql_type
     assert_equal 'citext', @column.sql_type
   end
 
+  def test_change_table_supports_json
+    @connection.transaction do
+      @connection.change_table('citexts') do |t|
+        t.citext 'username'
+      end
+      Citext.reset_column_information
+      column = Citext.columns.find { |c| c.name == 'username' }
+      assert_equal :citext, column.type
+
+      raise ActiveRecord::Rollback # reset the schema change
+    end
+  ensure
+    Citext.reset_column_information
+  end
+
   def test_write
     x = Citext.new(cival: 'Some CI Text')
-    assert x.save!
+    x.save!
+    citext = Citext.first
+    assert_equal "Some CI Text", citext.cival
+
+    citext.cival = "Some NEW CI Text"
+    citext.save!
+
+    assert_equal "Some NEW CI Text", citext.reload.cival
   end
 
   def test_select_case_insensitive
     @connection.execute "insert into citexts (cival) values('Cased Text')"
     x = Citext.where(cival: 'cased text').first
-    assert_equal('Cased Text', x.cival)
+    assert_equal 'Cased Text', x.cival
   end
-
-end
\ No newline at end of file
+end