add propertytesting for i32

Cargo.toml

@@ -36,6 +36,7 @@ num-traits = { version = "0.2.14", default-features = false }
 
 [dev-dependencies]
 criterion = "0.5.1"
+proptest = "1.4.0"
 
 [[bench]]
 name = "benches"

tests/i32.rs

@@ -0,0 +1,24 @@
+use proptest::prelude::proptest;
+use atoi::{FromRadix10, FromRadix10Signed};
+
+type N = i32;
+
+proptest! {
+    #[test]
+    fn roundtrip_without_sign(n in 0..=N::MAX) {
+        let text = n.to_string();
+        let (actual, len) = N::from_radix_10(text.as_bytes());
+
+        assert_eq!(text.len(), len);
+        assert_eq!(n, actual);
+    }
+
+    #[test]
+    fn roundtrip_with_sign(n in N::MIN..=N::MAX) {
+        let text = n.to_string();
+        let (actual, len) = N::from_radix_10_signed(text.as_bytes());
+
+        assert_eq!(text.len(), len);
+        assert_eq!(n, actual);
+    }
+}