diff --git a/tests/TestHarness.cpp b/tests/TestHarness.cpp
new file mode 100644
index 0000000..24b291e
--- /dev/null
+++ b/tests/TestHarness.cpp
@@ -0,0 +1,101 @@
+#include <iostream>
+#include <vector>
+#include <string>
+#include <cassert>
+
+#include "../src/NLPacketCodec.hpp"
+#include "../src/DomainDiscovery.hpp"
+
+static std::string hexOf(const std::vector<uint8_t>& v) {
+    static const char* hexd = "0123456789abcdef";
+    std::string out; out.resize(v.size()*2);
+    for (size_t i=0;i<v.size();++i){ out[2*i]=hexd[(v[i]>>4)&0xF]; out[2*i+1]=hexd[v[i]&0xF]; }
+    return out;
+}
+
+static std::string b64Of(const std::vector<uint8_t>& in){
+    static const char* tbl = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    std::string out; out.reserve(((in.size()+2)/3)*4);
+    size_t i=0; while(i<in.size()){
+        uint32_t val=0; int bytes=0;
+        for(int j=0;j<3;++j){ val<<=8; if(i<in.size()){ val|=in[i++]; ++bytes; } }
+        int pad = 3 - bytes;
+        for(int k=0;k<4-pad;++k){ int idx=(val>>(18-k*6))&0x3F; out.push_back(tbl[idx]); }
+        for(int k=0;k<pad;++k) out.push_back('=');
+    }
+    return out;
+}
+
+int main(){
+    int failures = 0;
+
+    // Test 1: protocol signature stability (for vendored Overte commit and current mapping)
+    {
+        auto sig = Overte::NLPacket::computeProtocolVersionSignature();
+        std::string hex = hexOf(sig);
+        std::string b64 = b64Of(sig);
+        std::cout << "[TEST] Protocol signature hex=" << hex << " base64=" << b64 << "\n";
+        // Expected values based on current repository state/logs
+        const std::string expectedHex = "2977ddf4352e7264b6a45767087b45ba";
+        if (hex != expectedHex) {
+            std::cerr << "[FAIL] Signature hex mismatch: got " << hex << " expected " << expectedHex << "\n";
+            ++failures;
+        }
+    }
+
+    // Test 2: discovery JSON parsing (Vircadia-like fields)
+    {
+        std::string json = R"JSON({
+            "data": [
+              {"name":"Alpha","network_address":"alpha.example.org","http_port":40102,"udp_port":40104},
+              {"name":"Beta","ice_server_address":"beta.example.org","http_port":40103,"udp_port":40105}
+            ]
+        })JSON";
+        auto domains = parseDomainsFromJson(json);
+        if (domains.size() < 2) {
+            std::cerr << "[FAIL] Parsed " << domains.size() << " entries, expected >=2\n";
+            ++failures;
+        } else {
+            if (domains[0].networkHost != "alpha.example.org" || domains[0].httpPort != 40102 || domains[0].udpPort != 40104) {
+                std::cerr << "[FAIL] First domain mismatch: host=" << domains[0].networkHost << " httpPort=" << domains[0].httpPort << " udpPort=" << domains[0].udpPort << "\n";
+                ++failures;
+            }
+            if (domains[1].networkHost != "beta.example.org" || domains[1].httpPort != 40103 || domains[1].udpPort != 40105) {
+                std::cerr << "[FAIL] Second domain mismatch: host=" << domains[1].networkHost << " httpPort=" << domains[1].httpPort << " udpPort=" << domains[1].udpPort << "\n";
+                ++failures;
+            }
+        }
+    }
+
+    // Test 3: discovery JSON parsing (Overte-like alternative keys)
+    {
+        std::string json = R"JSON({
+            "domains": [
+              {"name":"Gamma","address":"gamma.example.org","domain_http_port":40400,"domain_udp_port":40404},
+              {"name":"Delta","address":"delta.example.org"}
+            ]
+        })JSON";
+        auto domains = parseDomainsFromJson(json);
+        if (domains.empty()) {
+            std::cerr << "[FAIL] Parsed zero entries for alternative key set\n";
+            ++failures;
+        } else {
+            // find Gamma and Delta
+            bool gammaOK=false, deltaOK=false;
+            for (auto& d : domains) {
+                if (d.networkHost == "gamma.example.org" && d.httpPort == 40400 && d.udpPort == 40404) gammaOK = true;
+                if (d.networkHost == "delta.example.org" && d.httpPort == 40102 && d.udpPort == 40104) deltaOK = true; // defaults
+            }
+            if (!gammaOK) { std::cerr << "[FAIL] Gamma entry not found with expected ports\n"; ++failures; }
+            if (!deltaOK) { std::cerr << "[FAIL] Delta entry not found with default ports\n"; ++failures; }
+        }
+    }
+
+    if (failures == 0) {
+        std::cout << "ALL TESTS PASS" << std::endl;
+        return 0;
+    } else {
+        std::cout << failures << " TEST(S) FAILED" << std::endl;
+        return 1;
+    }
+}