Add true_bytes tests for ChaCha and Isaac; fix 2 bugs in fill_bytes i…

…mpls

[Cherry-picked from ae365ef]

src/prng/chacha.rs

@@ -328,6 +328,20 @@ mod test {
                         0x2c5bad8f, 0x898881dc, 0x5f1c86d9, 0xc1f8e7f4));
     }
 
+    #[test]
+    fn test_rng_true_bytes() {
+        let seed : &[_] = &[0u32; 8];
+        let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
+        let mut buf = [0u8; 32];
+        ra.fill_bytes(&mut buf);
+        // Same as first values in test_isaac_true_values as bytes in LE order
+        assert_eq!(buf,
+                   [118, 184, 224, 173, 160, 241, 61, 144,
+                    64, 93, 106, 229, 83, 134, 189, 40,
+                    189, 210, 25, 184, 160, 141, 237, 26,
+                    168, 54, 239, 204, 139, 119, 13, 199]);
+    }
+
     #[test]
     fn test_rng_clone() {
         let seed : &[_] = &[0u32; 8];

src/prng/isaac.rs

@@ -412,6 +412,20 @@ mod test {
                         1576568959, 3507990155, 179069555, 141456972, 2478885421));
     }
 
+    #[test]
+    fn test_isaac_true_bytes() {
+        let seed: &[_] = &[1, 23, 456, 7890, 12345];
+        let mut rng1 = IsaacRng::from_seed(seed);
+        let mut buf = [0u8; 32];
+        rng1.fill_bytes(&mut buf);
+        // Same as first values in test_isaac_true_values as bytes in LE order
+        assert_eq!(buf,
+                   [82, 186, 128, 152, 71, 240, 20, 52,
+                    45, 175, 180, 15, 86, 16, 99, 125,
+                    101, 203, 81, 214, 97, 162, 134, 250,
+                    103, 78, 203, 15, 150, 3, 210, 164]);
+    }
+
     #[test]
     fn test_isaac_new_uninitialized() {
         // Compare the results from initializing `IsaacRng` with

src/prng/isaac64.rs

@@ -373,7 +373,21 @@ mod test {
                         596345674630742204, 9947027391921273664, 11788097613744130851,
                         10391409374914919106));
     }
-
+
+    #[test]
+    fn test_isaac64_true_bytes() {
+        let seed: &[_] = &[1, 23, 456, 7890, 12345];
+        let mut rng1 = Isaac64Rng::from_seed(seed);
+        let mut buf = [0u8; 32];
+        rng1.fill_bytes(&mut buf);
+        // Same as first values in test_isaac64_true_values as bytes in LE order
+        assert_eq!(buf,
+                   [140, 237, 103, 8, 93, 196, 151, 7,
+                    156, 242, 26, 63, 54, 166, 135, 199,
+                    141, 186, 192, 50, 116, 69, 205, 240,
+                    98, 205, 127, 160, 83, 98, 49, 17]);
+    }
+
     #[test]
     fn test_isaac_new_uninitialized() {
         // Compare the results from initializing `IsaacRng` with