diff --git a/src/libraries/packed_felt252.cairo b/src/libraries/packed_felt252.cairo
index 3424c41..99a6f23 100644
--- a/src/libraries/packed_felt252.cairo
+++ b/src/libraries/packed_felt252.cairo
@@ -2,7 +2,7 @@ use core::traits::Into;
 use starknet::storage_access::{StorePacking};
 
 const TWO_POW_62: u256 = 0x4000000000000000; // 2**62
-const MASK_62: u256 = 0xFFFFFFFFFFFFFFFF; // 2**62 - 1
+const MASK_62: u256 = 0x3fffffffffffffff; // 2**62 - 1
 
 pub fn get_u62(packed: felt252, mut n: u8) -> u64 {
     assert(n < 4, 'Index out of bounds');
@@ -51,3 +51,118 @@ pub fn sum_u62(packed: felt252, mut s: u8, e: u8) -> u256 {
     };
     sum
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{get_u62, update_62, add_u62, sub_u62};
+
+    #[test]
+    fn test_get_u62() {
+        let packed: felt252 = 0x11111111111111103333333333333330888888888888888111111111111111;
+        assert_eq!(get_u62(packed, 0), 0x0111111111111111);
+        assert_eq!(get_u62(packed, 1), 0x0222222222222222);
+        assert_eq!(get_u62(packed, 2), 0x0333333333333333);
+        assert_eq!(get_u62(packed, 3), 0x0444444444444444);
+    }
+
+    #[test]
+    #[should_panic(expected: ('Index out of bounds',))]
+    fn test_get_u62_out_of_bounds() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        get_u62(packed, 4);
+    }
+
+    #[test]
+    fn test_update_62() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        let mut i = 0;
+        while (i < 4) {
+            let updated = update_62(packed, i, 0x0123456789ABCDEF);
+            let mut j = 0;
+            while (j < 4) {
+                if (j == i) {
+                    assert_eq!(get_u62(updated, j), 0x0123456789ABCDEF);
+                } else {
+                    assert_eq!(get_u62(updated, j), get_u62(packed, j));
+                }
+                j += 1;
+            };
+            i += 1;
+        };
+    }
+
+    #[test]
+    #[should_panic(expected: ('Index out of bounds',))]
+    fn test_update_64_out_of_bounds() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        update_62(packed, 4, 0x0123456789ABCDEF);
+    }
+
+    #[test]
+    fn test_add_u62() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        let base_hex = 0x0111111111111111;
+        let mut i = 0;
+        while (i < 4) {
+            let updated = add_u62(packed, i, base_hex);
+            let mut j = 0;
+            while (j < 4) {
+                if (j == i) {
+                    assert_eq!(get_u62(updated, j), base_hex * (i + 2).into());
+                } else {
+                    assert_eq!(get_u62(updated, j), get_u62(packed, j));
+                }
+                j += 1;
+            };
+            i += 1;
+        };
+    }
+
+    #[test]
+    #[should_panic(expected: ('Index out of bounds',))]
+    fn test_add_u62_out_of_bounds() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        add_u62(packed, 4, 0x1111111111111111);
+    }
+
+    #[test]
+    #[should_panic(expected: ('u64_add Overflow',))]
+    fn add_u62_overflow() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        add_u62(packed, 0, 0xffffffffffffffff);
+    }
+
+    #[test]
+    fn test_sub_u62() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        let base_hex = 0x0111111111111111;
+        let mut i = 0;
+        while (i < 4) {
+            let updated = sub_u62(packed, i, base_hex * i.into());
+            let mut j = 0;
+            while (j < 4) {
+                if (j == i) {
+                    assert_eq!(get_u62(updated, j), base_hex);
+                } else {
+                    assert_eq!(get_u62(updated, j), get_u62(packed, j));
+                }
+                j += 1;
+            };
+            i += 1;
+        };
+    }
+
+    #[test]
+    #[should_panic(expected: ('Index out of bounds',))]
+    fn test_sub_u62_out_of_bounds() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        sub_u62(packed, 4, 0x1111111111111111);
+    }
+
+    #[test]
+    #[should_panic(expected: ('u64_sub Overflow',))]
+    fn sub_u62_overflow() {
+        let packed = 0x11111111111111103333333333333330888888888888888111111111111111;
+        sub_u62(packed, 0, 0x0111111111111112);
+    }
+}