add number test

Author: tomoikey

tests/number.rs

@@ -0,0 +1,12 @@
+use refined_type::less_rule;
+use refined_type::result::Error;
+
+less_rule!((5, i8));
+
+#[test]
+fn test_less_than_5() -> Result<(), Error> {
+    let target = 4;
+    let refined = Less5i8::new(target)?;
+    assert_eq!(refined.into_value(), 4);
+    Ok(())
+}