test: add orm migration and transaction tests

test/test_orm_transaction.rb

@@ -0,0 +1,39 @@
+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+
+class OrmTransactionTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-tx-store')
+    @store = Prism::Orm::Store.new(File.join(@dir, 'test.pstore'))
+    @store.create_table(:ledger, %w[id amount])
+  end
+
+  def teardown
+    FileUtils.remove_entry(@dir)
+  end
+
+  def test_successful_transaction_commits_every_write
+    @store.transaction do
+      @store.insert(:ledger, amount: 10)
+      @store.insert(:ledger, amount: 20)
+    end
+    assert_equal [10, 20], @store.all(:ledger).map { |row| row['amount'] }
+  end
+
+  def test_failed_transaction_rolls_back_every_write
+    assert_raises(RuntimeError) do
+      @store.transaction do
+        @store.insert(:ledger, amount: 10)
+        @store.insert(:ledger, amount: 20)
+        raise 'transfer failed midway'
+      end
+    end
+    assert_empty @store.all(:ledger), 'no row from the aborted transaction should be visible'
+  end
+
+  def test_transaction_return_value_is_yielded_through
+    result = @store.transaction { @store.insert(:ledger, amount: 5) }
+    assert_equal 1, result
+  end
+end