payment tests

server/implementations/Catcrafts.Server-Eurc.cpp

@@ -216,6 +216,25 @@ bool JsonRpcIdIs(std::string_view json, std::int64_t want) {
     return static_cast<std::int64_t>(id->number) == want;
 }
 
+std::string BalanceOfCallData(std::string_view address) {
+    // Selector, then one 32-byte ABI word: 12 zero BYTES of left padding (24
+    // hex digits), then the 20 address bytes (40 hex digits). The first
+    // version of this appended 24 bytes of padding — bytes and hex digits
+    // confused — which shifted the address past the argument word. Solidity's
+    // decoder read the word's low 20 bytes (mostly padding plus the address's
+    // first 8 bytes), found a valid-looking address with nothing on it, and
+    // answered 0: every real payment read as "not arrived", with no error on
+    // either side. Pinned byte-for-byte in ShouldParseEurcChains, and proven
+    // against a real chain in ShouldSettleEurcOnTestnet — the suite that
+    // caught it.
+    std::string data;
+    data.reserve(2 + 8 + 64);
+    data += kBalanceOfSelector;
+    data.append(12 * 2, '0');
+    data += address.substr(2);
+    return data;
+}
+
 std::optional<std::int64_t> ParseEthCallUint(std::string_view json) {
     auto doc = Json::Parse(json);
     if (!doc || !doc->IsObject()) return std::nullopt;
@@ -809,13 +828,9 @@ private:
                                           const std::string& address) {
         // A node that is not serving this chain does not get to answer.
         if (!EndpointServesChain(chain, url)) return std::nullopt;
-        // eth_call to the token contract. The address is left-padded into a
-        // 32-byte ABI word: 24 zero bytes, then the 20 address bytes.
-        std::string data;
-        data.reserve(2 + 8 + 64);
-        data += kBalanceOfSelector;
-        data.append(24 * 2, '0');
-        data += address.substr(2);
+        // eth_call to the token contract; the calldata encoding lives in
+        // BalanceOfCallData, where the self-test can pin it.
+        const std::string data = BalanceOfCallData(address);
 
         const std::string body =
             std::string(R"({"jsonrpc":"2.0","id":1,"method":"eth_call","params":[{"to":")")