test(depinfo): current cargo unable to parse v0 or v1

We're going to add the magic marker in the next commit.
The v0 test is to ensure that we don't change anything unexpected.

Author: weihanglo

src/cargo/core/compiler/fingerprint/dep_info.rs

@@ -667,4 +667,35 @@ mod encoded_dep_info {
     fn round_trip_with_checksums() {
         gen_test(true);
     }
+
+    #[test]
+    fn path_type_is_u8_max() {
+        #[rustfmt::skip]
+        let data = [
+            0x01, 0x00, 0x00, 0x00, 0xff,       // magic marker
+            0x01,                               // version
+            0x01, 0x00, 0x00, 0x00,             // # of files
+            0x00,                               // path type
+            0x04, 0x00, 0x00, 0x00,             // len of path
+            0x72, 0x75, 0x73, 0x74,             // path bytes ("rust")
+            0x00,                               // cksum exists?
+            0x00, 0x00, 0x00, 0x00,             // # of env vars
+        ];
+        // The current cargo doesn't recognize the magic marker.
+        assert!(EncodedDepInfo::parse(&data).is_none());
+    }
+
+    #[test]
+    fn parse_v0_fingerprint_dep_info() {
+        #[rustfmt::skip]
+        let data = [
+            0x01, 0x00, 0x00, 0x00, // # of files
+            0x00,                   // path type
+            0x04, 0x00, 0x00, 0x00, // len of path
+            0x72, 0x75, 0x73, 0x74, // path bytes: "rust"
+            0x00, 0x00, 0x00, 0x00, // # of env vars
+        ];
+        // Cargo can't recognize v0 after `-Zchecksum-freshess` added.
+        assert!(EncodedDepInfo::parse(&data).is_none());
+    }
 }