[packet_transport] Minimise heap allocations (#14482)

esphome/components/packet_transport/packet_transport.cpp

@@ -3,6 +3,8 @@
 #include "esphome/core/helpers.h"
 #include "packet_transport.h"
 
+#include <ranges>
+
 #include "esphome/components/xxtea/xxtea.h"
 
 namespace esphome {
@@ -77,7 +79,7 @@ enum DecodeResult {
   DECODE_EMPTY,
 };
 
-static const size_t MAX_PING_KEYS = 4;
+static constexpr size_t MAX_PING_KEYS = 4;
 
 static inline void add(std::vector<uint8_t> &vec, uint32_t data) {
   vec.push_back(data & 0xFF);
@@ -168,7 +170,7 @@ class PacketDecoder {
     return true;
   }
 
-  bool decrypt(const uint32_t *key) {
+  bool decrypt(const uint32_t *key) const {
     if (this->get_remaining_size() % 4 != 0) {
       return false;
     }
@@ -249,9 +251,9 @@ void PacketTransport::init_data_() {
   } else {
     add(this->data_, DATA_KEY);
   }
-  for (const auto &pkey : this->ping_keys_) {
+  for (auto &value : this->ping_keys_ | std::views::values) {
     add(this->data_, PING_KEY);
-    add(this->data_, pkey.second);
+    add(this->data_, value);
   }
 }
 
@@ -331,7 +333,7 @@ void PacketTransport::update() {
   auto now = millis() / 1000;
   if (this->last_key_time_ + this->ping_pong_recyle_time_ < now) {
     this->resend_ping_key_ = this->ping_pong_enable_;
-    ESP_LOGV(TAG, "Ping request, age %u", now - this->last_key_time_);
+    ESP_LOGV(TAG, "Ping request, age %" PRIu32, now - this->last_key_time_);
     this->last_key_time_ = now;
   }
   for (const auto &provider : this->providers_) {
@@ -339,24 +341,32 @@ void PacketTransport::update() {
     if (key_response_age > (this->ping_pong_recyle_time_ * 2u)) {
 #ifdef USE_STATUS_SENSOR
       if (provider.second.status_sensor != nullptr && provider.second.status_sensor->state) {
-        ESP_LOGI(TAG, "Ping status for %s timeout at %u with age %u", provider.first.c_str(), now, key_response_age);
+        ESP_LOGI(TAG, "Ping status for %s timeout at %" PRIu32 " with age %" PRIu32, provider.first.c_str(), now,
+                 key_response_age);
         provider.second.status_sensor->publish_state(false);
       }
 #endif
 #ifdef USE_SENSOR
-      for (auto &sensor : this->remote_sensors_[provider.first]) {
+      auto it = this->remote_sensors_.find(provider.first);
-        sensor.second->publish_state(NAN);
+      if (it != this->remote_sensors_.end()) {
+        for (auto &val : it->second | std::views::values) {
+          val->publish_state(NAN);
+        }
       }
 #endif
 #ifdef USE_BINARY_SENSOR
-      for (auto &sensor : this->remote_binary_sensors_[provider.first]) {
+      auto bs_it = this->remote_binary_sensors_.find(provider.first);
-        sensor.second->invalidate_state();
+      if (bs_it != this->remote_binary_sensors_.end()) {
+        for (auto &val : bs_it->second | std::views::values) {
+          val->invalidate_state();
+        }
       }
 #endif
     } else {
 #ifdef USE_STATUS_SENSOR
       if (provider.second.status_sensor != nullptr && !provider.second.status_sensor->state) {
-        ESP_LOGI(TAG, "Ping status for %s restored at %u with age %u", provider.first.c_str(), now, key_response_age);
+        ESP_LOGI(TAG, "Ping status for %s restored at %" PRIu32 " with age %" PRIu32, provider.first.c_str(), now,
+                 key_response_age);
         provider.second.status_sensor->publish_state(true);
       }
 #endif
@@ -367,11 +377,16 @@ void PacketTransport::update() {
 void PacketTransport::add_key_(const char *name, uint32_t key) {
   if (!this->is_encrypted_())
     return;
-  if (this->ping_keys_.count(name) == 0 && this->ping_keys_.size() == MAX_PING_KEYS) {
+  auto it = this->ping_keys_.find(name);
-    ESP_LOGW(TAG, "Ping key from %s discarded", name);
+  if (it == this->ping_keys_.end()) {
-    return;
+    if (this->ping_keys_.size() == MAX_PING_KEYS) {
+      ESP_LOGW(TAG, "Ping key from %s discarded", name);
+      return;
+    }
+    this->ping_keys_.emplace(name, key);  // allocates string key once only
+  } else {
+    it->second = key;  // key string already exists in map, no allocation
   }
-  this->ping_keys_[name] = key;
   this->updated_ = true;
   ESP_LOGV(TAG, "Ping key from %s now %X", name, (unsigned) key);
 }
@@ -431,17 +446,19 @@ void PacketTransport::process_(std::span<const uint8_t> data) {
     return;
   }
 
-  if (this->providers_.count(namebuf) == 0) {
+  auto it = this->providers_.find(namebuf);
+  if (it == this->providers_.end()) {
     ESP_LOGVV(TAG, "Unknown hostname %s", namebuf);
     return;
   }
+  auto &provider = it->second;
   ESP_LOGV(TAG, "Found hostname %s", namebuf);
 
 #ifdef USE_SENSOR
-  auto &sensors = this->remote_sensors_[namebuf];
+  auto &sensors = this->remote_sensors_.try_emplace(namebuf).first->second;
 #endif
 #ifdef USE_BINARY_SENSOR
-  auto &binary_sensors = this->remote_binary_sensors_[namebuf];
+  auto &binary_sensors = this->remote_binary_sensors_.try_emplace(namebuf).first->second;
 #endif
 
   if (!decoder.bump_to(4)) {
@@ -453,7 +470,6 @@ void PacketTransport::process_(std::span<const uint8_t> data) {
     return;
   }
 
-  auto &provider = this->providers_[namebuf];
   // if encryption not used with this host, ping check is pointless since it would be easily spoofed.
   if (provider.encryption_key.empty())
     ping_key_seen = true;
@@ -495,16 +511,19 @@ void PacketTransport::process_(std::span<const uint8_t> data) {
     if (decoder.decode(BINARY_SENSOR_KEY, namebuf, sizeof(namebuf), byte) == DECODE_OK) {
       ESP_LOGV(TAG, "Got binary sensor %s %d", namebuf, byte);
 #ifdef USE_BINARY_SENSOR
-      if (binary_sensors.count(namebuf) != 0)
+      auto bs = binary_sensors.find(namebuf);
-        binary_sensors[namebuf]->publish_state(byte != 0);
+      if (bs != binary_sensors.end()) {
+        bs->second->publish_state(byte != 0);
+      }
 #endif
       continue;
     }
     if (decoder.decode(SENSOR_KEY, namebuf, sizeof(namebuf), rdata.u32) == DECODE_OK) {
       ESP_LOGV(TAG, "Got sensor %s %f", namebuf, rdata.f32);
 #ifdef USE_SENSOR
-      if (sensors.count(namebuf) != 0)
+      auto sensor_it = sensors.find(namebuf);
-        sensors[namebuf]->publish_state(rdata.f32);
+      if (sensor_it != sensors.end())
+        sensor_it->second->publish_state(rdata.f32);
 #endif
       continue;
     }
@@ -537,12 +556,18 @@ void PacketTransport::dump_config() {
     ESP_LOGCONFIG(TAG, "  Remote host: %s", host.first.c_str());
     ESP_LOGCONFIG(TAG, "    Encrypted: %s", YESNO(!host.second.encryption_key.empty()));
 #ifdef USE_SENSOR
-    for (const auto &sensor : this->remote_sensors_[host.first.c_str()])
+    auto rs = this->remote_sensors_.find(host.first.c_str());
-      ESP_LOGCONFIG(TAG, "    Sensor: %s", sensor.first.c_str());
+    if (rs != this->remote_sensors_.end()) {
+      for (const auto &key : rs->second | std::views::keys)
+        ESP_LOGCONFIG(TAG, "    Sensor: %s", key.c_str());
+    }
 #endif
 #ifdef USE_BINARY_SENSOR
-    for (const auto &sensor : this->remote_binary_sensors_[host.first.c_str()])
+    auto rbs = this->remote_binary_sensors_.find(host.first.c_str());
-      ESP_LOGCONFIG(TAG, "    Binary Sensor: %s", sensor.first.c_str());
+    if (rbs != this->remote_binary_sensors_.end()) {
+      for (const auto &key : rbs->second | std::views::keys)
+        ESP_LOGCONFIG(TAG, "    Binary Sensor: %s", key.c_str());
+    }
 #endif
   }
 }

esphome/components/packet_transport/packet_transport.h

@@ -24,6 +24,9 @@
 namespace esphome {
 namespace packet_transport {
 
+// std::less provides allocation-free comparison with const char *
+template<typename T> using string_map_t = std::map<std::string, T, std::less<>>;
+
 struct Provider {
   std::vector<uint8_t> encryption_key;
   const char *name;
@@ -79,15 +82,15 @@ class PacketTransport : public PollingComponent {
 #endif
 
   void add_provider(const char *hostname) {
-    if (this->providers_.count(hostname) == 0) {
+    if (!this->providers_.contains(hostname)) {
       Provider provider{};
       provider.name = hostname;
       this->providers_[hostname] = provider;
 #ifdef USE_SENSOR
-      this->remote_sensors_[hostname] = std::map<std::string, sensor::Sensor *>();
+      this->remote_sensors_[hostname] = string_map_t<sensor::Sensor *>();
 #endif
 #ifdef USE_BINARY_SENSOR
-      this->remote_binary_sensors_[hostname] = std::map<std::string, binary_sensor::BinarySensor *>();
+      this->remote_binary_sensors_[hostname] = string_map_t<binary_sensor::BinarySensor *>();
 #endif
     }
   }
@@ -139,23 +142,23 @@ class PacketTransport : public PollingComponent {
 
 #ifdef USE_SENSOR
   std::vector<Sensor> sensors_{};
-  std::map<std::string, std::map<std::string, sensor::Sensor *>> remote_sensors_{};
+  string_map_t<string_map_t<sensor::Sensor *>> remote_sensors_{};
 #endif
 #ifdef USE_BINARY_SENSOR
   std::vector<BinarySensor> binary_sensors_{};
-  std::map<std::string, std::map<std::string, binary_sensor::BinarySensor *>> remote_binary_sensors_{};
+  string_map_t<string_map_t<binary_sensor::BinarySensor *>> remote_binary_sensors_{};
 #endif
 
-  std::map<std::string, Provider> providers_{};
+  string_map_t<Provider> providers_{};
   std::vector<uint8_t> ping_header_{};
   std::vector<uint8_t> header_{};
   std::vector<uint8_t> data_{};
-  std::map<std::string, uint32_t> ping_keys_{};
+  string_map_t<uint32_t> ping_keys_{};
   const char *platform_name_{""};
   void add_key_(const char *name, uint32_t key);
   void send_ping_pong_request_();
 
-  inline bool is_encrypted_() { return !this->encryption_key_.empty(); }
+  bool is_encrypted_() const { return !this->encryption_key_.empty(); }
 };
 
 }  // namespace packet_transport

script/cpp_unit_test.py

@@ -12,6 +12,7 @@ from esphome.__main__ import command_compile, parse_args
 from esphome.config import validate_config
 from esphome.core import CORE
 from esphome.platformio_api import get_idedata
+from esphome.yaml_util import load_yaml
 
 # This must coincide with the version in /platformio.ini
 PLATFORMIO_GOOGLE_TEST_LIB = "google/googletest@^1.15.2"
@@ -44,6 +45,38 @@ def filter_components_without_tests(components: list[str]) -> list[str]:
     return filtered_components
 
 
+# Name of optional per-component YAML config merged into the test build
+# before validation so that platform defines (USE_SENSOR, etc.) are generated.
+CPP_TEST_CONFIG_FILE = "cpp_test.yaml"
+
+
+def load_component_test_configs(components: list[str]) -> dict:
+    """Load cpp_test.yaml files from test component directories.
+
+    These configs are merged into the base test config *before* validation
+    so that entity registration runs during code generation, which causes
+    the corresponding USE_* defines to be emitted.
+    """
+    merged: dict = {}
+    for component in components:
+        config_file = COMPONENTS_TESTS_DIR / component / CPP_TEST_CONFIG_FILE
+        if not config_file.exists():
+            continue
+        component_config = load_yaml(config_file)
+        if not component_config:
+            continue
+        for key, value in component_config.items():
+            if (
+                key in merged
+                and isinstance(merged[key], list)
+                and isinstance(value, list)
+            ):
+                merged[key].extend(value)
+            else:
+                merged[key] = value
+    return merged
+
+
 def create_test_config(config_name: str, includes: list[str]) -> dict:
     """Create ESPHome test configuration for C++ unit tests.
 
@@ -115,6 +148,11 @@ def run_tests(selected_components: list[str]) -> int:
 
     config = create_test_config(config_name, includes)
 
+    # Merge component-specific test configs (e.g. sensor instances) before
+    # validation so that entity registration and USE_* defines work.
+    extra_config = load_component_test_configs(components)
+    config.update(extra_config)
+
     CORE.config_path = COMPONENTS_TESTS_DIR / "dummy.yaml"
     CORE.dashboard = None
 
@@ -122,8 +160,10 @@ def run_tests(selected_components: list[str]) -> int:
     config = validate_config(config, {})
 
     # Add all components and dependencies to the base configuration after validation, so their files
-    # are added to the build.
+    # are added to the build.  Use setdefault to avoid overwriting entries that were
-    config.update({key: {} for key in components_with_dependencies})
+    # already validated (e.g. sensor instances from cpp_test.yaml).
+    for key in components_with_dependencies:
+        config.setdefault(key, {})
 
     print(f"Testing components: {', '.join(components)}")
     CORE.config = config

tests/components/packet_transport/common.h

@@ -0,0 +1,98 @@
+#pragma once
+#include <cstdint>
+#include <cstring>
+#include <cstdio>
+#include <vector>
+#include <gtest/gtest.h>
+#include "esphome/components/packet_transport/packet_transport.h"
+
+namespace esphome::packet_transport::testing {
+
+// Protocol constants mirrored from packet_transport.cpp for test packet construction.
+static constexpr uint16_t MAGIC_NUMBER = 0x4553;
+static constexpr uint16_t MAGIC_PING = 0x5048;
+
+// Concrete testable implementation of PacketTransport.
+// Captures sent packets and exposes protected members for verification.
+//
+// Sensor round-trip tests require USE_SENSOR / USE_BINARY_SENSOR to be defined,
+// which happens when 'sensor' and 'binary_sensor' components are in the build.
+// Run with --all or include those components to enable the full test suite.
+class TestablePacketTransport : public PacketTransport {
+ public:
+  using PacketTransport::add_key_;
+  using PacketTransport::data_;
+  using PacketTransport::encryption_key_;
+  using PacketTransport::flush_;
+  using PacketTransport::header_;
+  using PacketTransport::increment_code_;
+  using PacketTransport::init_data_;
+  using PacketTransport::is_encrypted_;
+  using PacketTransport::is_provider_;
+  using PacketTransport::name_;
+  using PacketTransport::ping_key_;
+  using PacketTransport::ping_keys_;
+  using PacketTransport::ping_pong_enable_;
+  using PacketTransport::ping_pong_recyle_time_;
+  using PacketTransport::process_;
+  using PacketTransport::providers_;
+  using PacketTransport::rolling_code_;
+  using PacketTransport::rolling_code_enable_;
+  using PacketTransport::send_data_;
+  using PacketTransport::updated_;
+#ifdef USE_SENSOR
+  using PacketTransport::add_data_;
+  using PacketTransport::remote_sensors_;
+  using PacketTransport::sensors_;
+#endif
+#ifdef USE_BINARY_SENSOR
+  using PacketTransport::add_binary_data_;
+  using PacketTransport::binary_sensors_;
+  using PacketTransport::remote_binary_sensors_;
+#endif
+
+  // NOTE: std::vector is used here for test convenience. For production code,
+  // consider using StaticVector or FixedVector from esphome/core/helpers.h instead.
+  mutable std::vector<std::vector<uint8_t>> sent_packets;
+  size_t max_packet_size{512};
+  bool send_enabled{true};
+
+  void send_packet(const std::vector<uint8_t> &buf) const override { this->sent_packets.push_back(buf); }
+  size_t get_max_packet_size() override { return this->max_packet_size; }
+  bool should_send() override { return this->send_enabled; }
+
+  /// Build the packet header for testing without requiring App or global_preferences.
+  void init_for_test(const char *name) {
+    this->name_ = name;
+    this->header_.clear();
+    // MAGIC_NUMBER as uint16_t little-endian
+    this->header_.push_back(MAGIC_NUMBER & 0xFF);
+    this->header_.push_back((MAGIC_NUMBER >> 8) & 0xFF);
+    // Length-prefixed hostname
+    auto len = strlen(name);
+    this->header_.push_back(static_cast<uint8_t>(len));
+    for (size_t i = 0; i < len; i++)
+      this->header_.push_back(name[i]);
+    // Pad to 4-byte boundary
+    while (this->header_.size() & 0x3)
+      this->header_.push_back(0);
+  }
+};
+
+/// Build a MAGIC_PING packet for testing add_key_ / ping-pong flows.
+inline std::vector<uint8_t> build_ping_packet(const char *hostname, uint32_t key) {
+  std::vector<uint8_t> packet;
+  packet.push_back(MAGIC_PING & 0xFF);
+  packet.push_back((MAGIC_PING >> 8) & 0xFF);
+  auto len = strlen(hostname);
+  packet.push_back(static_cast<uint8_t>(len));
+  for (size_t i = 0; i < len; i++)
+    packet.push_back(hostname[i]);
+  packet.push_back(key & 0xFF);
+  packet.push_back((key >> 8) & 0xFF);
+  packet.push_back((key >> 16) & 0xFF);
+  packet.push_back((key >> 24) & 0xFF);
+  return packet;
+}
+
+}  // namespace esphome::packet_transport::testing

tests/components/packet_transport/cpp_test.yaml

@@ -0,0 +1,11 @@
+# Extra component configuration required by C++ unit tests.
+# Loaded by cpp_unit_test.py and merged into the test build config
+# before validation, so that platform defines (USE_SENSOR, etc.) are generated.
+
+sensor:
+  - platform: template
+    id: test_cpp_sensor
+
+binary_sensor:
+  - platform: template
+    id: test_cpp_binary_sensor

tests/components/packet_transport/packet_transport_test.cpp

@@ -0,0 +1,445 @@
+#include "common.h"
+
+namespace esphome::packet_transport::testing {
+
+// --- Configuration setter tests ---
+
+TEST(PacketTransportTest, SetIsProvider) {
+  TestablePacketTransport transport;
+  transport.set_is_provider(true);
+  EXPECT_TRUE(transport.is_provider_);
+}
+
+TEST(PacketTransportTest, SetEncryptionKey) {
+  TestablePacketTransport transport;
+  std::vector<uint8_t> key(32, 0xAB);
+  transport.set_encryption_key(key);
+  EXPECT_EQ(transport.encryption_key_, key);
+  EXPECT_TRUE(transport.is_encrypted_());
+}
+
+TEST(PacketTransportTest, NoEncryptionByDefault) {
+  TestablePacketTransport transport;
+  EXPECT_FALSE(transport.is_encrypted_());
+}
+
+TEST(PacketTransportTest, SetRollingCodeEnable) {
+  TestablePacketTransport transport;
+  transport.set_rolling_code_enable(true);
+  EXPECT_TRUE(transport.rolling_code_enable_);
+}
+
+TEST(PacketTransportTest, SetPingPongEnable) {
+  TestablePacketTransport transport;
+  transport.set_ping_pong_enable(true);
+  EXPECT_TRUE(transport.ping_pong_enable_);
+}
+
+TEST(PacketTransportTest, SetPingPongRecycleTime) {
+  TestablePacketTransport transport;
+  transport.set_ping_pong_recycle_time(600);
+  EXPECT_EQ(transport.ping_pong_recyle_time_, 600u);
+}
+
+// --- Provider management ---
+
+TEST(PacketTransportTest, AddProvider) {
+  TestablePacketTransport transport;
+  transport.add_provider("host1");
+  EXPECT_TRUE(transport.providers_.contains("host1"));
+  EXPECT_EQ(transport.providers_.size(), 1u);
+}
+
+TEST(PacketTransportTest, AddProviderDuplicate) {
+  TestablePacketTransport transport;
+  transport.add_provider("host1");
+  transport.add_provider("host1");
+  EXPECT_EQ(transport.providers_.size(), 1u);
+}
+
+TEST(PacketTransportTest, SetProviderEncryption) {
+  TestablePacketTransport transport;
+  transport.add_provider("host1");
+  std::vector<uint8_t> key(32, 0xCD);
+  transport.set_provider_encryption("host1", key);
+  EXPECT_EQ(transport.providers_["host1"].encryption_key, key);
+}
+
+// --- Sensor management (requires USE_SENSOR / USE_BINARY_SENSOR) ---
+
+#ifdef USE_SENSOR
+TEST(PacketTransportTest, AddSensor) {
+  TestablePacketTransport transport;
+  sensor::Sensor s;
+  transport.add_sensor("temp", &s);
+  ASSERT_EQ(transport.sensors_.size(), 1u);
+  EXPECT_STREQ(transport.sensors_[0].id, "temp");
+  EXPECT_EQ(transport.sensors_[0].sensor, &s);
+  EXPECT_TRUE(transport.sensors_[0].updated);
+}
+
+TEST(PacketTransportTest, AddRemoteSensor) {
+  TestablePacketTransport transport;
+  sensor::Sensor s;
+  transport.add_remote_sensor("host1", "remote_temp", &s);
+  EXPECT_TRUE(transport.providers_.contains("host1"));
+  EXPECT_EQ(transport.remote_sensors_["host1"]["remote_temp"], &s);
+}
+#endif
+
+#ifdef USE_BINARY_SENSOR
+TEST(PacketTransportTest, AddBinarySensor) {
+  TestablePacketTransport transport;
+  binary_sensor::BinarySensor bs;
+  transport.add_binary_sensor("motion", &bs);
+  ASSERT_EQ(transport.binary_sensors_.size(), 1u);
+  EXPECT_STREQ(transport.binary_sensors_[0].id, "motion");
+  EXPECT_EQ(transport.binary_sensors_[0].sensor, &bs);
+}
+
+TEST(PacketTransportTest, AddRemoteBinarySensor) {
+  TestablePacketTransport transport;
+  binary_sensor::BinarySensor bs;
+  transport.add_remote_binary_sensor("host1", "remote_motion", &bs);
+  EXPECT_TRUE(transport.providers_.contains("host1"));
+  EXPECT_EQ(transport.remote_binary_sensors_["host1"]["remote_motion"], &bs);
+}
+#endif
+
+// --- Unencrypted round-trip tests (require USE_SENSOR / USE_BINARY_SENSOR) ---
+
+#ifdef USE_SENSOR
+TEST(PacketTransportTest, UnencryptedSensorRoundTrip) {
+  // Encoder
+  TestablePacketTransport encoder;
+  encoder.init_for_test("sender");
+  sensor::Sensor local_sensor;
+  local_sensor.state = 42.5f;
+  encoder.add_sensor("temp", &local_sensor);
+
+  encoder.send_data_(true);
+  ASSERT_EQ(encoder.sent_packets.size(), 1u);
+
+  // Decoder
+  TestablePacketTransport decoder;
+  decoder.init_for_test("receiver");
+  sensor::Sensor remote_sensor;
+  remote_sensor.state = -999.0f;  // sentinel
+  decoder.add_remote_sensor("sender", "temp", &remote_sensor);
+
+  auto &packet = encoder.sent_packets[0];
+  decoder.process_({packet.data(), packet.size()});
+  EXPECT_FLOAT_EQ(remote_sensor.state, 42.5f);
+}
+#endif
+
+#ifdef USE_BINARY_SENSOR
+TEST(PacketTransportTest, UnencryptedBinarySensorRoundTrip) {
+  TestablePacketTransport encoder;
+  encoder.init_for_test("sender");
+  binary_sensor::BinarySensor local_bs;
+  local_bs.state = true;
+  encoder.add_binary_sensor("motion", &local_bs);
+
+  encoder.send_data_(true);
+  ASSERT_EQ(encoder.sent_packets.size(), 1u);
+
+  TestablePacketTransport decoder;
+  decoder.init_for_test("receiver");
+  binary_sensor::BinarySensor remote_bs;
+  decoder.add_remote_binary_sensor("sender", "motion", &remote_bs);
+
+  auto &packet = encoder.sent_packets[0];
+  decoder.process_({packet.data(), packet.size()});
+  EXPECT_TRUE(remote_bs.state);
+}
+#endif
+
+#if defined(USE_SENSOR) && defined(USE_BINARY_SENSOR)
+TEST(PacketTransportTest, MultipleSensorsRoundTrip) {
+  TestablePacketTransport encoder;
+  encoder.init_for_test("sender");
+
+  sensor::Sensor s1, s2;
+  s1.state = 10.0f;
+  s2.state = 20.0f;
+  encoder.add_sensor("s1", &s1);
+  encoder.add_sensor("s2", &s2);
+
+  binary_sensor::BinarySensor bs1;
+  bs1.state = true;
+  encoder.add_binary_sensor("bs1", &bs1);
+
+  encoder.send_data_(true);
+  ASSERT_EQ(encoder.sent_packets.size(), 1u);
+
+  TestablePacketTransport decoder;
+  decoder.init_for_test("receiver");
+  sensor::Sensor rs1, rs2;
+  binary_sensor::BinarySensor rbs1;
+  rs1.state = -999.0f;
+  rs2.state = -999.0f;
+  decoder.add_remote_sensor("sender", "s1", &rs1);
+  decoder.add_remote_sensor("sender", "s2", &rs2);
+  decoder.add_remote_binary_sensor("sender", "bs1", &rbs1);
+
+  auto &packet = encoder.sent_packets[0];
+  decoder.process_({packet.data(), packet.size()});
+
+  EXPECT_FLOAT_EQ(rs1.state, 10.0f);
+  EXPECT_FLOAT_EQ(rs2.state, 20.0f);
+  EXPECT_TRUE(rbs1.state);
+}
+#endif
+
+// --- Encrypted round-trip ---
+
+#ifdef USE_SENSOR
+TEST(PacketTransportTest, EncryptedSensorRoundTrip) {
+  std::vector<uint8_t> key(32);
+  for (int i = 0; i < 32; i++)
+    key[i] = i;
+
+  TestablePacketTransport encoder;
+  encoder.init_for_test("sender");
+  encoder.set_encryption_key(key);
+  sensor::Sensor local_sensor;
+  local_sensor.state = 99.9f;
+  encoder.add_sensor("temp", &local_sensor);
+
+  encoder.send_data_(true);
+  ASSERT_EQ(encoder.sent_packets.size(), 1u);
+
+  TestablePacketTransport decoder;
+  decoder.init_for_test("receiver");
+  sensor::Sensor remote_sensor;
+  remote_sensor.state = -999.0f;
+  decoder.add_remote_sensor("sender", "temp", &remote_sensor);
+  decoder.set_provider_encryption("sender", key);
+
+  auto &packet = encoder.sent_packets[0];
+  decoder.process_({packet.data(), packet.size()});
+  EXPECT_FLOAT_EQ(remote_sensor.state, 99.9f);
+}
+
+// --- Selective send ---
+
+TEST(PacketTransportTest, SendDataOnlyUpdated) {
+  TestablePacketTransport encoder;
+  encoder.init_for_test("sender");
+
+  sensor::Sensor s1, s2;
+  s1.state = 1.0f;
+  s2.state = 2.0f;
+  encoder.add_sensor("s1", &s1);
+  encoder.add_sensor("s2", &s2);
+
+  // Mark s1 as not updated, only s2 as updated
+  encoder.sensors_[0].updated = false;
+  encoder.sensors_[1].updated = true;
+
+  encoder.send_data_(false);
+  ASSERT_EQ(encoder.sent_packets.size(), 1u);
+
+  TestablePacketTransport decoder;
+  decoder.init_for_test("receiver");
+  sensor::Sensor rs1, rs2;
+  rs1.state = -999.0f;
+  rs2.state = -999.0f;
+  decoder.add_remote_sensor("sender", "s1", &rs1);
+  decoder.add_remote_sensor("sender", "s2", &rs2);
+
+  auto &packet = encoder.sent_packets[0];
+  decoder.process_({packet.data(), packet.size()});
+
+  EXPECT_FLOAT_EQ(rs1.state, -999.0f);  // not updated, not sent
+  EXPECT_FLOAT_EQ(rs2.state, 2.0f);     // updated, sent
+}
+#endif
+
+// --- Ping key tests ---
+
+TEST(PacketTransportTest, PingKeyStoredWhenEncrypted) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  transport.set_encryption_key(std::vector<uint8_t>(32, 0xAA));
+
+  auto ping = build_ping_packet("requester", 0xDEADBEEF);
+  transport.process_({ping.data(), ping.size()});
+
+  ASSERT_EQ(transport.ping_keys_.size(), 1u);
+  EXPECT_EQ(transport.ping_keys_["requester"], 0xDEADBEEFu);
+}
+
+TEST(PacketTransportTest, PingKeyIgnoredWhenNotEncrypted) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  // No encryption key — add_key_ should be a no-op
+
+  auto ping = build_ping_packet("requester", 0xDEADBEEF);
+  transport.process_({ping.data(), ping.size()});
+
+  EXPECT_TRUE(transport.ping_keys_.empty());
+}
+
+TEST(PacketTransportTest, PingKeyUpdatedOnRepeat) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  transport.set_encryption_key(std::vector<uint8_t>(32, 0xAA));
+
+  auto ping1 = build_ping_packet("host1", 0x1111);
+  transport.process_({ping1.data(), ping1.size()});
+  EXPECT_EQ(transport.ping_keys_["host1"], 0x1111u);
+
+  // Same host, new key value — should update in place
+  auto ping2 = build_ping_packet("host1", 0x2222);
+  transport.process_({ping2.data(), ping2.size()});
+  EXPECT_EQ(transport.ping_keys_.size(), 1u);
+  EXPECT_EQ(transport.ping_keys_["host1"], 0x2222u);
+}
+
+TEST(PacketTransportTest, PingKeyMaxLimit) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  transport.set_encryption_key(std::vector<uint8_t>(32, 0xAA));
+
+  // Fill to MAX_PING_KEYS (4)
+  for (int i = 0; i < 4; i++) {
+    char name[16];
+    snprintf(name, sizeof(name), "host%d", i);
+    auto ping = build_ping_packet(name, 0x1000 + i);
+    transport.process_({ping.data(), ping.size()});
+  }
+  EXPECT_EQ(transport.ping_keys_.size(), 4u);
+
+  // 5th key should be discarded
+  auto ping = build_ping_packet("host4", 0x9999);
+  transport.process_({ping.data(), ping.size()});
+  EXPECT_EQ(transport.ping_keys_.size(), 4u);
+  EXPECT_FALSE(transport.ping_keys_.contains("host4"));
+}
+
+#ifdef USE_SENSOR
+TEST(PacketTransportTest, PingKeyIncludedInTransmittedPacket) {
+  std::vector<uint8_t> key(32, 0xBB);
+
+  // Responder: encrypted, owns a sensor
+  TestablePacketTransport responder;
+  responder.init_for_test("responder");
+  responder.set_encryption_key(key);
+  sensor::Sensor local_sensor;
+  local_sensor.state = 77.7f;
+  responder.add_sensor("temp", &local_sensor);
+
+  // Requester sends a MAGIC_PING that the responder processes
+  auto ping = build_ping_packet("requester", 0xDEADBEEF);
+  responder.process_({ping.data(), ping.size()});
+  ASSERT_EQ(responder.ping_keys_.size(), 1u);
+
+  // Responder sends sensor data — ping key should be embedded
+  responder.send_data_(true);
+  ASSERT_EQ(responder.sent_packets.size(), 1u);
+
+  // Requester: encrypted provider, ping-pong enabled, expects key 0xDEADBEEF
+  TestablePacketTransport requester;
+  requester.init_for_test("requester");
+  requester.set_ping_pong_enable(true);
+  requester.ping_key_ = 0xDEADBEEF;
+  sensor::Sensor remote_sensor;
+  remote_sensor.state = -999.0f;
+  requester.add_remote_sensor("responder", "temp", &remote_sensor);
+  requester.set_provider_encryption("responder", key);
+
+  // The requester decrypts the packet and finds its ping key echoed back,
+  // which gates the sensor data — if the key is missing, data is blocked.
+  auto &packet = responder.sent_packets[0];
+  requester.process_({packet.data(), packet.size()});
+  EXPECT_FLOAT_EQ(remote_sensor.state, 77.7f);
+}
+
+TEST(PacketTransportTest, MissingPingKeyBlocksSensorData) {
+  std::vector<uint8_t> key(32, 0xBB);
+
+  // Responder sends data WITHOUT receiving any MAGIC_PING first — no ping keys
+  TestablePacketTransport responder;
+  responder.init_for_test("responder");
+  responder.set_encryption_key(key);
+  sensor::Sensor local_sensor;
+  local_sensor.state = 77.7f;
+  responder.add_sensor("temp", &local_sensor);
+  responder.send_data_(true);
+  ASSERT_EQ(responder.sent_packets.size(), 1u);
+
+  // Requester with ping-pong enabled expects a key that isn't in the packet
+  TestablePacketTransport requester;
+  requester.init_for_test("requester");
+  requester.set_ping_pong_enable(true);
+  requester.ping_key_ = 0xDEADBEEF;
+  sensor::Sensor remote_sensor;
+  remote_sensor.state = -999.0f;
+  requester.add_remote_sensor("responder", "temp", &remote_sensor);
+  requester.set_provider_encryption("responder", key);
+
+  auto &packet = responder.sent_packets[0];
+  requester.process_({packet.data(), packet.size()});
+  EXPECT_FLOAT_EQ(remote_sensor.state, -999.0f);  // blocked — ping key not found
+}
+#endif
+
+// --- Process error handling ---
+
+TEST(PacketTransportTest, ProcessShortBuffer) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  uint8_t buf[] = {0x53};
+  // Too short for a magic number - should return safely
+  transport.process_({buf, 1});
+}
+
+TEST(PacketTransportTest, ProcessBadMagic) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  uint8_t buf[] = {0xFF, 0xFF, 0x00, 0x00};
+  // Wrong magic - should return safely
+  transport.process_({buf, sizeof(buf)});
+}
+
+TEST(PacketTransportTest, ProcessOwnHostname) {
+  TestablePacketTransport transport;
+  transport.init_for_test("myself");
+  // Build a packet from "myself" using a separate encoder
+  TestablePacketTransport fake_sender;
+  fake_sender.init_for_test("myself");
+  fake_sender.send_data_(true);
+  ASSERT_EQ(fake_sender.sent_packets.size(), 1u);
+
+  auto &packet = fake_sender.sent_packets[0];
+  // Should be silently ignored because hostname matches our own
+  transport.process_({packet.data(), packet.size()});
+}
+
+TEST(PacketTransportTest, ProcessUnknownHostname) {
+  TestablePacketTransport transport;
+  transport.init_for_test("receiver");
+  // No providers registered - "unknown" will not be found
+  TestablePacketTransport sender;
+  sender.init_for_test("unknown");
+  sender.send_data_(true);
+  ASSERT_EQ(sender.sent_packets.size(), 1u);
+
+  auto &packet = sender.sent_packets[0];
+  // Should return safely without crash
+  transport.process_({packet.data(), packet.size()});
+}
+
+// --- Send disabled ---
+
+TEST(PacketTransportTest, NoSendWhenDisabled) {
+  TestablePacketTransport transport;
+  transport.init_for_test("sender");
+  transport.send_enabled = false;
+  transport.send_data_(true);
+  EXPECT_TRUE(transport.sent_packets.empty());
+}
+
+}  // namespace esphome::packet_transport::testing