More serialization tests & compressed structs

sampling/src/source.rs

@@ -15,11 +15,16 @@ impl Source {
     }
 
     pub fn branch(&mut self) -> ([u8; 32], Self) {
-        let mut seed = [0; 32];
-        self.source.fill_bytes(&mut seed);
+        let seed: [u8; 32] = self.new_seed();
         (seed, Source::new(seed))
     }
 
+    pub fn new_seed(&mut self) -> [u8; 32] {
+        let mut seed: [u8; 32] = [0u8; 32];
+        self.fill_bytes(&mut seed);
+        seed
+    }
+
     #[inline(always)]
     pub fn next_u64n(&mut self, max: u64, mask: u64) -> u64 {
         let mut x: u64 = self.next_u64() & mask;