Cover parsing/serializing roundtrip in fuzzers

fuzz/fuzz_targets/parse_dictionary.rs

@@ -1,7 +1,18 @@
 #![no_main]
 
 use libfuzzer_sys::fuzz_target;
+use sfv::SerializeValue as _;
 
 fuzz_target!(|data: &[u8]| {
-    let _ = sfv::Parser::from_bytes(data).parse_dictionary();
+    if let Ok(dict) = sfv::Parser::from_bytes(data).parse_dictionary() {
+        let serialized = dict.serialize_value();
+        if dict.is_empty() {
+            assert!(serialized.is_err());
+        } else {
+            assert_eq!(
+                sfv::Parser::from_bytes(serialized.unwrap().as_bytes()).parse_dictionary(),
+                Ok(dict)
+            );
+        }
+    }
 });

fuzz/fuzz_targets/parse_item.rs

@@ -1,7 +1,14 @@
 #![no_main]
 
 use libfuzzer_sys::fuzz_target;
+use sfv::SerializeValue as _;
 
 fuzz_target!(|data: &[u8]| {
-    let _ = sfv::Parser::from_bytes(data).parse_item();
+    if let Ok(item) = sfv::Parser::from_bytes(data).parse_item() {
+        let serialized = item.serialize_value().unwrap();
+        assert_eq!(
+            sfv::Parser::from_bytes(serialized.as_bytes()).parse_item(),
+            Ok(item)
+        );
+    }
 });

fuzz/fuzz_targets/parse_list.rs

@@ -1,7 +1,18 @@
 #![no_main]
 
 use libfuzzer_sys::fuzz_target;
+use sfv::SerializeValue as _;
 
 fuzz_target!(|data: &[u8]| {
-    let _ = sfv::Parser::from_bytes(data).parse_list();
+    if let Ok(list) = sfv::Parser::from_bytes(data).parse_list() {
+        let serialized = list.serialize_value();
+        if list.is_empty() {
+            assert!(serialized.is_err());
+        } else {
+            assert_eq!(
+                sfv::Parser::from_bytes(serialized.unwrap().as_bytes()).parse_list(),
+                Ok(list)
+            );
+        }
+    }
 });