Added test case and updated changelog

Author: aidanharan

CHANGELOG.md

@@ -17,5 +17,6 @@
 - [#1320](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/1320) Fix SQL statement to calculate `updated_at` when upserting.
 - [#1327](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/1327) Fix multiple `nil` identity columns for merge insert.
 - [#1338](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/1338) Fix `insert_all`/`upsert_all` for table names containing numbers.
+- [#1345](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/1345) Maintain index options during `change_column` operations.
 
 Please check [8-0-stable](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/blob/8-0-stable/CHANGELOG.md) for previous changes.

test/cases/change_column_index_test_sqlserver.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require "cases/helper_sqlserver"
+
+class ChangeColumnIndexTestSqlServer < ActiveRecord::TestCase
+  class CreateClientsWithUniqueIndex < ActiveRecord::Migration[8.0]
+    def up
+      create_table :clients do |t|
+        t.string :name, limit: 15
+      end
+      add_index :clients, :name, unique: true
+    end
+
+    def down
+      drop_table :clients
+    end
+  end
+
+  class ChangeClientsNameLength < ActiveRecord::Migration[8.0]
+    def up
+      change_column :clients, :name, :string, limit: 30
+    end
+  end
+
+  before do
+    CreateClientsWithUniqueIndex.new.up
+  end
+
+  after do
+    CreateClientsWithUniqueIndex.new.down
+  end
+
+  def test_index_uniqueness_is_maintained_after_column_change
+    indexes = ActiveRecord::Base.connection.indexes("clients")
+    columns = ActiveRecord::Base.connection.columns("clients")
+    assert_equal columns.find { |column| column.name == "name" }.limit, 15
+    assert_equal indexes.size, 1
+    assert_equal indexes.first.name, "index_clients_on_name"
+    assert indexes.first.unique
+
+    ChangeClientsNameLength.new.up
+
+    indexes = ActiveRecord::Base.connection.indexes("clients")
+    columns = ActiveRecord::Base.connection.columns("clients")
+    assert_equal columns.find { |column| column.name == "name" }.limit, 30
+    assert_equal indexes.size, 1
+    assert_equal indexes.first.name, "index_clients_on_name"
+    assert indexes.first.unique
+  end
+end