Output random bytes to logs in hexadecimal form

include/ableton/link/NodeId.hpp

@@ -23,6 +23,7 @@
 #include <algorithm>
 #include <array>
 #include <cstdint>
+#include <iomanip>
 #include <string>
 
 namespace ableton
@@ -55,7 +56,18 @@ struct NodeId : NodeIdArray
 
   friend std::ostream& operator<<(std::ostream& stream, const NodeId& id)
   {
-    return stream << std::string{id.cbegin(), id.cend()};
+    const auto flags = stream.flags();
+    const auto fill = stream.fill();
+
+    stream << "0x" << std::hex << std::setfill('0');
+    for (const auto byte : id)
+    {
+      stream << std::setw(2) << static_cast<int>(byte);
+    }
+
+    stream.flags(flags);
+    stream.fill(fill);
+    return stream;
   }
 
   template <typename It>

src/CMakeLists.txt

@@ -25,6 +25,7 @@ set(link_core_test_SOURCES
   ableton/link/tst_LinearRegression.cpp
   ableton/link/tst_Measurement.cpp
   ableton/link/tst_Median.cpp
+  ableton/link/tst_NodeId.cpp
   ableton/link/tst_Peers.cpp
   ableton/link/tst_PeerState.cpp
   ableton/link/tst_Phase.cpp

src/ableton/link/tst_NodeId.cpp

@@ -0,0 +1,96 @@
+/* Copyright 2025, Ableton AG, Berlin. All rights reserved.
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *  If you would like to incorporate Link into a proprietary software application,
+ *  please contact <link-devs@ableton.com>.
+ */
+
+#include <ableton/link/NodeId.hpp>
+#include <ableton/test/CatchWrapper.hpp>
+#include <sstream>
+
+namespace ableton
+{
+namespace link
+{
+
+TEST_CASE("NodeId")
+{
+  SECTION("StreamState")
+  {
+    NodeId nodeId{};
+    nodeId.fill(0xAB);
+
+    std::ostringstream stream;
+
+    // Set up some non-default stream state
+    stream << std::dec << std::setfill('X') << std::setw(5) << 42;
+    // After setw, width resets to 0, but fill and flags should persist
+
+    // Capture stream state before outputting NodeId
+    const auto flagsBefore = stream.flags();
+    const auto fillBefore = stream.fill();
+
+    // Output the NodeId
+    stream << nodeId;
+
+    // Check stream state after outputting NodeId
+    const auto flagsAfter = stream.flags();
+    const auto fillAfter = stream.fill();
+
+    CHECK(flagsBefore == flagsAfter);
+    CHECK(fillBefore == fillAfter);
+  }
+
+
+  SECTION("StreamOutputFormat")
+  {
+    NodeId nodeId{};
+    nodeId.fill(0x00);
+    nodeId[0] = 0x01;
+    nodeId[7] = 0xFF;
+
+    std::ostringstream stream;
+    stream << nodeId;
+
+    CHECK(stream.str() == "0x01000000000000ff");
+  }
+
+  SECTION("StreamStateVisual")
+  {
+    NodeId nodeId{};
+    nodeId.fill(0xAB);
+
+    std::ostringstream stream;
+
+    // Output something before NodeId with specific formatting
+    stream << std::setfill('_') << std::setw(5) << 42;
+    CHECK(stream.str() == "___42");
+
+    // Output the NodeId
+    stream << " " << nodeId << " ";
+
+    // Now output something after - it should use decimal and default fill
+    // If stream state is corrupted, this will be in hex and/or use '0' fill
+    stream << std::setw(5) << 15;
+
+    // Expected: "___42 0xabababababababab ___15"
+    // If corrupted: "___42 0xabababababababab 0000f" (hex + '0' fill)
+    CHECK(stream.str() == "___42 0xabababababababab ___15");
+  }
+}
+
+} // namespace link
+} // namespace ableton