diff --git a/src/format/formulas.rs b/src/format/formulas.rs
index 8f24906..805a745 100644
--- a/src/format/formulas.rs
+++ b/src/format/formulas.rs
@@ -364,6 +364,16 @@ mod tests
 	use crate::*;
 	use crate::format::terms::tests::*;
 
+	fn assert_all<F>(input: F, output: &str)
+	where
+		F: Fn(Box<Fn(Box<Formula>) -> Box<Formula>>) -> Box<Formula>,
+	{
+		assert_eq!(format(input(Box::new(|f| f))), output);
+		assert_eq!(format(input(Box::new(|f| and(vec![f])))), output);
+		assert_eq!(format(input(Box::new(|f| or(vec![f])))), output);
+		assert_eq!(format(input(Box::new(|f| if_and_only_if(vec![f])))), output);
+	}
+
 	fn format(formula: Box<ast::Formula>) -> String
 	{
 		format!("{}", formula)