[cpptests] support testing platform components (#13075)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>

tests/components/README.md

@@ -7,10 +7,23 @@
 testing binaries that combine many components. By convention, this unique namespace is `esphome::component::testing`
 (where "component" is the component under test), for example: `esphome::uart::testing`.
 
+### Platform components
+
+For components that expose to a platform component, create a folder under your component test folder with the platform component name, e.g. `binary_sensor` and
+include the relevant `.cpp` and `.h` test files there.
+
+### Override component code generation for testing
+
+When generating code for testing, ESPHome won't invoke the component's `to_code` function, since most components do not
+need to generate configuration code for testing.
+
+If you do need to generate code to for example configure compilation flags or add libraries,
+add the component name to the `CPP_TESTING_CODEGEN_COMPONENTS` allowlist in `script/cpp_unit_test.py`.
 
 ## Running component unit tests
 
 (from the repository root)
+
 ```bash
 ./script/cpp_unit_test.py component1 component2 ...
 ```

tests/components/packet_transport/binary_sensor/binary_sensor_test.cpp

@@ -0,0 +1,77 @@
+#include "../common.h"
+
+namespace esphome::packet_transport::testing {
+
+TEST(PacketTransportBinarySensorTest, 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(PacketTransportBinarySensorTest, 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);
+}
+
+TEST(PacketTransportBinarySensorTest, 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);
+}
+
+TEST(PacketTransportBinarySensorTest, 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);
+}
+
+}  // namespace esphome::packet_transport::testing

tests/components/packet_transport/cpp_test.yaml

@@ -1,11 +0,0 @@
-# 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

@@ -65,198 +65,6 @@ TEST(PacketTransportTest, SetProviderEncryption) {
   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) {
@@ -319,73 +127,6 @@ TEST(PacketTransportTest, PingKeyMaxLimit) {
   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) {

tests/components/packet_transport/sensor/sensor_test.cpp

@@ -0,0 +1,170 @@
+#include "../common.h"
+
+namespace esphome::packet_transport::testing {
+
+TEST(PacketTransportSensorTest, 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(PacketTransportSensorTest, 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);
+}
+
+TEST(PacketTransportSensorTest, 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);
+}
+
+TEST(PacketTransportSensorTest, 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);
+}
+
+TEST(PacketTransportSensorTest, 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
+}
+
+TEST(PacketTransportSensorTest, 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(PacketTransportSensorTest, 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
+}
+
+}  // namespace esphome::packet_transport::testing

tests/script/test_helpers.py

@@ -1027,6 +1027,73 @@ def test_get_all_dependencies_empty_set() -> None:
     assert result == set()
 
 
+def test_get_all_dependencies_platform_component() -> None:
+    """Platform components (domain.component) are looked up via get_platform,
+    not get_component."""
+    platform_comp = Mock()
+    platform_comp.dependencies = []
+    platform_comp.auto_load = []
+
+    with (
+        patch("esphome.loader.get_component") as mock_get_component,
+        patch("helpers.get_platform") as mock_get_platform,
+    ):
+        mock_get_platform.return_value = platform_comp
+        mock_get_component.return_value = None
+
+        result = helpers.get_all_dependencies({"sensor.bthome"})
+
+        mock_get_platform.assert_called_once_with("sensor", "bthome")
+        mock_get_component.assert_not_called()
+        assert result == {"sensor.bthome"}
+
+
+def test_get_all_dependencies_platform_component_with_dependencies() -> None:
+    """Dependencies of a platform component are resolved transitively."""
+    platform_comp = Mock()
+    platform_comp.dependencies = ["sensor"]
+    platform_comp.auto_load = []
+
+    sensor_comp = Mock()
+    sensor_comp.dependencies = []
+    sensor_comp.auto_load = []
+
+    with (
+        patch("esphome.loader.get_component") as mock_get_component,
+        patch("helpers.get_platform") as mock_get_platform,
+    ):
+        mock_get_platform.return_value = platform_comp
+        mock_get_component.side_effect = lambda name: (
+            sensor_comp if name == "sensor" else None
+        )
+
+        result = helpers.get_all_dependencies({"sensor.bthome"})
+
+        assert result == {"sensor.bthome", "sensor"}
+
+
+def test_get_all_dependencies_cpp_testing_flag() -> None:
+    """cpp_testing=True propagates to CORE.cpp_testing during resolution."""
+    from esphome.core import CORE
+
+    with (
+        patch("esphome.loader.get_component") as mock_get_component,
+        patch("esphome.loader.get_platform"),
+    ):
+        observed: list[bool] = []
+
+        def capturing_get_component(name: str):
+            observed.append(CORE.cpp_testing)
+
+        mock_get_component.side_effect = capturing_get_component
+
+        helpers.get_all_dependencies({"some_comp"}, cpp_testing=True)
+
+    assert observed and all(observed), (
+        "CORE.cpp_testing should be True during resolution"
+    )
+
+
 def test_get_components_from_integration_fixtures() -> None:
     """Test extraction of components from fixture YAML files."""
     yaml_content = {

tests/unit_tests/test_core.py

@@ -841,6 +841,18 @@ class TestEsphomeCore:
 
         assert "WiFi" in target.platformio_libraries
 
+    def test_testing_ensure_platform_registered__sets_count(self, target):
+        """Test testing_ensure_platform_registered sets count to 1 for new platform."""
+        assert target.platform_counts["sensor"] == 0
+        target.testing_ensure_platform_registered("sensor")
+        assert target.platform_counts["sensor"] == 1
+
+    def test_testing_ensure_platform_registered__does_not_overwrite(self, target):
+        """Test testing_ensure_platform_registered preserves existing count."""
+        target.platform_counts["sensor"] = 3
+        target.testing_ensure_platform_registered("sensor")
+        assert target.platform_counts["sensor"] == 3
+
     def test_add_library__extracts_short_name_from_path(self, target):
         """Test add_library extracts short name from library paths like owner/lib."""
         target.data[const.KEY_CORE] = {