test sqrt

src/utils/sqrt.rs

@@ -1,6 +1,14 @@
 use num_bigint::{BigInt, ToBigInt};
 use num_traits::{ToPrimitive, Zero};
 
+/// Computes floor(sqrt(value))
+///
+/// # Arguments
+///
+/// * `value`: The value for which to compute the square root, rounded down
+///
+/// returns: BigInt
+///
 fn sqrt(value: &BigInt) -> BigInt {
     assert!(*value >= Zero::zero(), "NEGATIVE");
 
@@ -25,3 +33,36 @@ fn sqrt(value: &BigInt) -> BigInt {
 
     z
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use num_traits::Num;
+
+    #[test]
+    fn test_sqrt_0_1000() {
+        for i in 0..1000 {
+            let sqrt_i = sqrt(&BigInt::from(i));
+            assert_eq!(sqrt_i, BigInt::from((i as f64).sqrt().floor() as i64));
+        }
+    }
+
+    #[test]
+    fn test_sqrt_2_powers() {
+        for i in 0..256 {
+            let root = BigInt::from(2).pow(i as u32);
+            let root_squared = &root * &root;
+            assert_eq!(sqrt(&root_squared), root);
+        }
+    }
+
+    #[test]
+    fn test_sqrt_max_uint256() {
+        let max_uint256_string =
+            "115792089237316195423570985008687907853269984665640564039457584007913129639935";
+        let max_uint256 = BigInt::from_str_radix(max_uint256_string, 10).unwrap();
+        let expected_sqrt =
+            BigInt::from_str_radix("340282366920938463463374607431768211455", 10).unwrap();
+        assert_eq!(sqrt(&max_uint256), expected_sqrt);
+    }
+}