diff --git a/activerecord/test/cases/migration/compatibility_test.rb b/activerecord/test/cases/migration/compatibility_test.rb
index b50d68d6df..2fef2f796e 100644
--- a/activerecord/test/cases/migration/compatibility_test.rb
+++ b/activerecord/test/cases/migration/compatibility_test.rb
@@ -71,9 +71,6 @@ module ActiveRecord
 
         assert_not connection.index_exists?(:more_testings, :foo_id)
         assert_not connection.index_exists?(:more_testings, :bar_id)
-
-        legacy_ref = connection.columns(:more_testings).find { |c| c.name == "foo_id" }
-        assert_not legacy_ref.bigint?
       ensure
         connection.drop_table :more_testings rescue nil
       end
@@ -133,11 +130,9 @@ module ActiveRecord
   end
 end
 
-class LegacyPrimaryKeyTest < ActiveRecord::TestCase
+module LegacyPrimaryKeyTestCases
   include SchemaDumpingHelper
 
-  self.use_transactional_tests = false
-
   class LegacyPrimaryKey < ActiveRecord::Base
   end
 
@@ -155,7 +150,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   end
 
   def test_legacy_primary_key_should_be_auto_incremented
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_table :legacy_primary_keys do |t|
           t.references :legacy_ref
@@ -185,7 +180,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   def test_legacy_integer_primary_key_should_not_be_auto_incremented
     skip if current_adapter?(:SQLite3Adapter)
 
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_table :legacy_primary_keys, id: :integer do |t|
         end
@@ -204,7 +199,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
 
   if current_adapter?(:Mysql2Adapter, :PostgreSQLAdapter)
     def test_legacy_primary_key_in_create_table_should_be_integer
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: false do |t|
             t.primary_key :id
@@ -219,7 +214,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     end
 
     def test_legacy_primary_key_in_change_table_should_be_integer
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: false do |t|
             t.integer :dummy
@@ -237,7 +232,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     end
 
     def test_add_column_with_legacy_primary_key_should_be_integer
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: false do |t|
             t.integer :dummy
@@ -254,7 +249,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   end
 
   def test_legacy_join_table_foreign_keys_should_be_integer
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_join_table :apples, :bananas do |t|
         end
@@ -269,7 +264,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
   end
 
   def test_legacy_join_table_column_options_should_be_overwritten
-    @migration = Class.new(ActiveRecord::Migration[5.0]) {
+    @migration = Class.new(migration_class) {
       def change
         create_join_table :apples, :bananas, column_options: { type: :bigint } do |t|
         end
@@ -285,7 +280,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
 
   if current_adapter?(:Mysql2Adapter)
     def test_legacy_bigint_primary_key_should_be_auto_incremented
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: :bigint
         end
@@ -302,7 +297,7 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     end
   else
     def test_legacy_bigint_primary_key_should_not_be_auto_incremented
-      @migration = Class.new(ActiveRecord::Migration[5.0]) {
+      @migration = Class.new(migration_class) {
         def change
           create_table :legacy_primary_keys, id: :bigint do |t|
           end
@@ -320,3 +315,27 @@ class LegacyPrimaryKeyTest < ActiveRecord::TestCase
     end
   end
 end
+
+module LegacyPrimaryKeyTest
+  class V5_0 < ActiveRecord::TestCase
+    include LegacyPrimaryKeyTestCases
+
+    self.use_transactional_tests = false
+
+    private
+      def migration_class
+        ActiveRecord::Migration[5.0]
+      end
+  end
+
+  class V4_2 < ActiveRecord::TestCase
+    include LegacyPrimaryKeyTestCases
+
+    self.use_transactional_tests = false
+
+    private
+      def migration_class
+        ActiveRecord::Migration[4.2]
+      end
+  end
+end