chore: checkpoint before Python removal

vendor/p256/tests/scalar.rs

@@ -0,0 +1,22 @@
+//! Scalar arithmetic tests.
+
+#![cfg(feature = "arithmetic")]
+
+use elliptic_curve::ops::{Invert, Reduce};
+use p256::{Scalar, U256};
+use proptest::prelude::*;
+
+prop_compose! {
+    fn scalar()(bytes in any::<[u8; 32]>()) -> Scalar {
+        <Scalar as Reduce<U256>>::reduce_bytes(&bytes.into())
+    }
+}
+
+proptest! {
+    #[test]
+    fn invert_and_invert_vartime_are_equivalent(w in scalar()) {
+        let inv: Option<Scalar> = w.invert().into();
+        let inv_vartime: Option<Scalar> = w.invert_vartime().into();
+        prop_assert_eq!(inv, inv_vartime);
+    }
+}