chore: test with ensure

ruby/retryable/main_test.rb

@@ -38,4 +38,24 @@ def test_error
     end
   end
 
+  def test_error_with_ensure
+    ensure_callback = lambda do |retries|
+      Logger.new(STDOUT).info("total attempts: #{retries}")
+    end
+
+    error = assert_raises RuntimeError do
+      Retryable.retryable(
+        on:         StandardError,
+        sleep:      0.1,
+        tries:      3,
+        log_method: log_method,
+        ensure:  ensure_callback
+      ) do
+        raise_error
+      end
+    end
+
+    # Even though we put ensure block, the error will be thrown if retries exhausted
+    assert_equal("100% error", error.message)
+  end
 end