diff --git a/src/format/terms.rs b/src/format/terms.rs
index 89e83f2..a42073e 100644
--- a/src/format/terms.rs
+++ b/src/format/terms.rs
@@ -435,6 +435,16 @@ mod tests
 		// TODO: escape functions that start with capital letters or that conflict with keywords
 	}
 
+	#[test]
+	fn format_function_declaration()
+	{
+		assert_eq!(format!("{}", function_declaration("a", 0)), "a/0");
+		assert_eq!(format!("{}", function_declaration("constant", 0)), "constant/0");
+		assert_eq!(format!("{}", function_declaration("f", 1)), "f/1");
+		assert_eq!(format!("{}", function_declaration("f", 3)), "f/3");
+		assert_eq!(format!("{}", function_declaration("function", 3)), "function/3");
+	}
+
 	#[test]
 	fn format_variable()
 	{