Add unit tests for SliceRandom trait and shuffle functionality

src/random/seq.rs

@@ -14,3 +14,63 @@ impl<T> SliceRandom for [T] {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::random::{CryptoRng, Prng};
+
+    #[test]
+    fn test_shuffle_slice() {
+        let mut rng = Prng::new(3);
+        let mut arr = [1, 2, 3, 4, 5];
+        let orig = arr.clone();
+        arr.shuffle(&mut rng);
+        assert_eq!(arr.len(), orig.len());
+        let mut sorted = arr.to_vec();
+        sorted.sort();
+        assert_eq!(sorted, orig.to_vec());
+    }
+
+    #[test]
+    fn test_slice_shuffle_deterministic_with_prng() {
+        let mut rng1 = Prng::new(11);
+        let mut rng2 = Prng::new(11);
+        let mut a = [1u8, 2, 3, 4, 5, 6, 7, 8, 9];
+        let mut b = a.clone();
+        a.shuffle(&mut rng1);
+        b.shuffle(&mut rng2);
+        assert_eq!(a, b);
+    }
+
+    #[test]
+    fn test_slice_shuffle_crypto_random_changes() {
+        let mut rng1 = CryptoRng::new();
+        let mut rng2 = CryptoRng::new();
+        let orig = [1u8, 2, 3, 4, 5, 6, 7, 8, 9];
+        let mut a = orig.clone();
+        let mut b = orig.clone();
+        a.shuffle(&mut rng1);
+        b.shuffle(&mut rng2);
+        assert!(a != orig || b != orig, "Shuffles did not change order");
+        assert_ne!(a, b, "Two Crypto RNG shuffles produced same order");
+    }
+
+    #[test]
+    fn test_shuffle_single_element_no_change() {
+        let mut rng = Prng::new(1);
+        let mut arr = [42];
+        arr.shuffle(&mut rng);
+        assert_eq!(arr, [42]);
+    }
+
+    #[test]
+    fn test_multiple_shuffles_different_results() {
+        let mut rng = Prng::new(5);
+        let mut arr1 = [1, 2, 3, 4];
+        let mut arr2 = [1, 2, 3, 4];
+        arr1.shuffle(&mut rng);
+        arr2.shuffle(&mut rng);
+        assert_ne!(arr1, arr2);
+    }
+}