GITBOOK-88: Add Preimage with length prefix part

docs/operations/test-runtime-upgrades.md

@@ -53,7 +53,22 @@ $ b2sum -l 256 preimage.bin | awk '{print "0x"$1}'
 $ export PREIMAGE_HASH=0x15165c85152568b7f523e374ce1a5172f2aa148721d5dae0441f86c201c1a77b4
 ```
 
-6. Create a chopsticks configuration file for the Polkadot relay chain, substituting the values generated previously: 
+6. Prepend compact-encoded length prefix to preimage, and convert back to hex, save as PREIMAGE\_WITH\_LENGTH\_PREFIX:
+
+```rust
+use codec::Encode;
+use std::fs::File;
+
+fn main() {
+    let mut file = File::open("preimage.bin")?;
+    let mut buf: Vec<u8> = Vec::new();
+    file.read_to_end(&mut buf)?;
+    let bytes_encoded = buf.encode();
+    println!("0x{}", hex::encode(bytes_encoded));
+}
+```
+
+7. Create a chopsticks configuration file for the Polkadot relay chain, substituting the values generated previously:&#x20;
 
 `polkadot.yml`
 
@@ -81,7 +96,7 @@ import-storage:
     }
 ```
 
-7. Use these Chopstics config files for AssetHub and BridgeHub
+8. Use these Chopstics config files for AssetHub and BridgeHub
 
 `polkadot-asset-hub.yml`
 
@@ -117,15 +132,15 @@ import-storage:
             free: 1000000000000000
 ```
 
-8. Run Chopsticks
+9. Run Chopsticks
 
 ```sh
 yarn start xcm -r polkadot.yml -p polkadot-asset-hub.yml -p polkadot-bridge-hub.yml
 ```
 
 A verification step that can be performed to see if the preimage has been added successfully is to check the `preimage` storage in the chain state. The authorized preimage should be in the list of added preimages.
 
-9. Execute the upgrade on the relay chain using Polkadot-JS:
+10. Execute the upgrade on the relay chain using Polkadot-JS:
 
 ```rust
 const number = (await api.rpc.chain.getHeader()).number.toNumber()
@@ -156,29 +171,29 @@ await api.rpc('dev_setStorage', {
 await api.rpc('dev_newBlock', { count: 1 })
 ```
 
-10. Advance a few blocks on the relay chain
+11. Advance a few blocks on the relay chain
 
 ```rust
 await api.rpc('dev_newBlock', { count: 2 })
 ```
 
-11. Advance by one block on bridgehub (not sure if necessary, need to experiment)
+12. Advance by one block on bridgehub (not sure if necessary, need to experiment)
 
 ```rust
 await api.rpc('dev_newBlock', { count: 1 })
 ```
 
-12. Now that the upgrade has been authorized on BridgeHub, we can execute the upgrade by calling parachainSystem.enactAuthorizedUpgrade, passing the parachain WASM blob previously generated by opengov-cli:
+13. Now that the upgrade has been authorized on BridgeHub, we can execute the upgrade by calling parachainSystem.enactAuthorizedUpgrade, passing the parachain WASM blob previously generated by opengov-cli:
 
 <figure><img src="../.gitbook/assets/image.png" alt=""><figcaption></figcaption></figure>
 
-12. Advance a few blocks on both bridgehub AND the relay chain
+14. Advance a few blocks on both bridgehub AND the relay chain
 
 ```rust
 await api.rpc('dev_newBlock', { count: 1 })
 ```
 
-14. The parachain should now be upgraded.
+15. The parachain should now be upgraded.
 
 ## Caveats