gnd(test): Document lowercase hex requirement for assertions

graph-node returns all hex-encoded values (addresses, tx hashes, bytes)
in lowercase. Add a note in the Assertions section's comparison behavior
table and in Tips & Best Practices.

Event inputs are normalised automatically and can be mixed case.

Also fix the transfer.json fixture assertion to use lowercase token ID.

Author: dimitrovmaksim

gnd/docs/gnd-test.md

@@ -383,8 +383,24 @@ GraphQL queries to validate the indexed entity state after processing all blocks
 | Arrays | **Order-insensitive** (set comparison) |
 | String vs Number | Coerced — `"123"` matches `123` |
 | Nulls/Booleans | Strict equality |
+| Hex strings | **Must be lowercase** — graph-node returns all hex values in lowercase |
 
-**Important:** Arrays are compared as sets (order doesn't matter). If you need ordered results, use `orderBy` in your GraphQL query:
+**Important:** Arrays are compared as sets (order doesn't matter).
+
+**Important:** graph-node returns all hex-encoded values (addresses, transaction hashes, byte arrays) in **lowercase**. Expected values in assertions must match exactly — mixed-case hex will not match:
+
+```json
+{
+  "expected": {
+    "transfer": {
+      "from": "0xaaaa000000000000000000000000000000000000",  // ✅ lowercase
+      "to":   "0xBBBB000000000000000000000000000000000000"   // ❌ will not match
+    }
+  }
+}
+```
+
+Note: hex values in event inputs (`params`, `address`) are normalized automatically and can be mixed case. If you need ordered results, use `orderBy` in your GraphQL query:
 
 ```json
 {
@@ -592,23 +608,33 @@ my-subgraph/
 
 ## Tips & Best Practices
 
-### Use Lowercase Addresses
+### Use Lowercase Hex in Assertions
 
-Always use lowercase hex addresses with `0x` prefix:
+graph-node returns **all** hex-encoded values in lowercase — addresses, transaction hashes, and any `Bytes`/`ID` fields. Expected values in assertions must use lowercase hex:
 
 ```json
 {
-  "address": "0x731a10897d267e19b34503ad902d0a29173ba4b1"  // ✅ Correct
+  "expected": {
+    "transfer": {
+      "from": "0xaaaa000000000000000000000000000000000000"  // ✅ lowercase
+    }
+  }
 }
 ```
 
 Not:
 ```json
 {
-  "address": "0x731A10897D267E19B34503Ad902d0A29173Ba4B1"  // ❌ Mixed case
+  "expected": {
+    "transfer": {
+      "from": "0xAAAA000000000000000000000000000000000000"  // ❌ will not match
+    }
+  }
 }
 ```
 
+Event inputs (`address`, `params`) are normalized automatically and can be mixed case.
+
 ### Test One Thing at a Time
 
 Write focused tests that validate a single behavior:

gnd/tests/fixtures/gnd_test/subgraph/tests/transfer.json

@@ -50,7 +50,7 @@
   "assertions": [
     {
       "query": "{ tokens { id name symbol decimals } }",
-      "expected": { "tokens": [ { "id": "0x9623063377AD1B27544C965cCd7342f7EA7e88C7", "name": "TheGraph", "symbol": "GRT", "decimals": 18 } ] }
+      "expected": { "tokens": [ { "id": "0x9623063377ad1b27544c965ccd7342f7ea7e88c7", "name": "TheGraph", "symbol": "GRT", "decimals": 18 } ] }
     },
     {
       "query": "{ accounts { id balances { token { symbol } amount } } }",