Add the max_delta filter (#12605)

Co-authored-by: clydebarrow <2366188+clydebarrow@users.noreply.github.com>

esphome/components/api/homeassistant_service.h

@@ -25,9 +25,7 @@ template<typename... X> class TemplatableStringValue : public TemplatableValue<s
 
  private:
   // Helper to convert value to string - handles the case where value is already a string
-  template<typename T> static std::string value_to_string(T &&val) {
-    return to_string(std::forward<T>(val));  // NOLINT
-  }
+  template<typename T> static std::string value_to_string(T &&val) { return to_string(std::forward<T>(val)); }
 
   // Overloads for string types - needed because std::to_string doesn't support them
   static std::string value_to_string(char *val) {

esphome/components/esp32_ble/ble_uuid.h

@@ -48,7 +48,7 @@ class ESPBTUUID {
 
   // Remove before 2026.8.0
   ESPDEPRECATED("Use to_str() instead. Removed in 2026.8.0", "2026.2.0")
-  std::string to_string() const;  // NOLINT
+  std::string to_string() const;
   const char *to_str(std::span<char, UUID_STR_LEN> output) const;
 
  protected:

esphome/components/sensor/__init__.py

@@ -9,6 +9,7 @@ from esphome.const import (
     CONF_ABOVE,
     CONF_ACCURACY_DECIMALS,
     CONF_ALPHA,
+    CONF_BASELINE,
     CONF_BELOW,
     CONF_CALIBRATION,
     CONF_DEVICE_CLASS,
@@ -38,7 +39,6 @@ from esphome.const import (
     CONF_TIMEOUT,
     CONF_TO,
     CONF_TRIGGER_ID,
-    CONF_TYPE,
     CONF_UNIT_OF_MEASUREMENT,
     CONF_VALUE,
     CONF_WEB_SERVER,
@@ -107,7 +107,7 @@ from esphome.const import (
 )
 from esphome.core import CORE, CoroPriority, coroutine_with_priority
 from esphome.core.entity_helpers import entity_duplicate_validator, setup_entity
-from esphome.cpp_generator import MockObjClass
+from esphome.cpp_generator import MockObj, MockObjClass
 from esphome.util import Registry
 
 CODEOWNERS = ["@esphome/core"]
@@ -574,38 +574,56 @@ async def lambda_filter_to_code(config, filter_id):
     return automation.new_lambda_pvariable(filter_id, lambda_, StatelessLambdaFilter)
 
 
-DELTA_SCHEMA = cv.Schema(
-    {
-        cv.Required(CONF_VALUE): cv.positive_float,
-        cv.Optional(CONF_TYPE, default="absolute"): cv.one_of(
-            "absolute", "percentage", lower=True
-        ),
-    }
+def validate_delta_value(value):
+    if isinstance(value, str) and value.endswith("%"):
+        # Check it's a well-formed percentage, but return the string as-is
+        try:
+            cv.positive_float(value[:-1])
+            return value
+        except cv.Invalid as exc:
+            raise cv.Invalid("Malformed delta % value") from exc
+    return cv.positive_float(value)
+
+
+# This ideally would be done with `cv.maybe_simple_value` but it doesn't seem to respect the default for min_value.
+DELTA_SCHEMA = cv.Any(
+    cv.All(
+        {
+            # Ideally this would be 'default=float("inf")' but it doesn't translate well to C++
+            cv.Optional(CONF_MAX_VALUE): validate_delta_value,
+            cv.Optional(CONF_MIN_VALUE, default="0.0"): validate_delta_value,
+            cv.Optional(CONF_BASELINE): cv.templatable(cv.float_),
+        },
+        cv.has_at_least_one_key(CONF_MAX_VALUE, CONF_MIN_VALUE),
+    ),
+    validate_delta_value,
 )
 
 
-def validate_delta(config):
-    try:
-        value = cv.positive_float(config)
-        return DELTA_SCHEMA({CONF_VALUE: value, CONF_TYPE: "absolute"})
-    except cv.Invalid:
-        pass
-    try:
-        value = cv.percentage(config)
-        return DELTA_SCHEMA({CONF_VALUE: value, CONF_TYPE: "percentage"})
-    except cv.Invalid:
-        pass
-    raise cv.Invalid("Delta filter requires a positive number or percentage value.")
+def _get_delta(value):
+    if isinstance(value, str):
+        assert value.endswith("%")
+        return 0.0, float(value[:-1])
+    return value, 0.0
 
 
-@FILTER_REGISTRY.register("delta", DeltaFilter, cv.Any(DELTA_SCHEMA, validate_delta))
+@FILTER_REGISTRY.register("delta", DeltaFilter, DELTA_SCHEMA)
 async def delta_filter_to_code(config, filter_id):
-    percentage = config[CONF_TYPE] == "percentage"
-    return cg.new_Pvariable(
-        filter_id,
-        config[CONF_VALUE],
-        percentage,
-    )
+    # The config could be just the min_value, or it could be a dict.
+    max = MockObj("std::numeric_limits<float>::infinity()"), 0
+    if isinstance(config, dict):
+        min = _get_delta(config[CONF_MIN_VALUE])
+        if CONF_MAX_VALUE in config:
+            max = _get_delta(config[CONF_MAX_VALUE])
+    else:
+        min = _get_delta(config)
+    var = cg.new_Pvariable(filter_id, *min, *max)
+    if isinstance(config, dict) and (baseline_lambda := config.get(CONF_BASELINE)):
+        baseline = await cg.process_lambda(
+            baseline_lambda, [(float, "x")], return_type=float
+        )
+        cg.add(var.set_baseline(baseline))
+    return var
 
 
 @FILTER_REGISTRY.register("or", OrFilter, validate_filters)

esphome/components/sensor/filter.cpp

@@ -291,22 +291,27 @@ optional<float> ThrottleWithPriorityFilter::new_value(float value) {
 }
 
 // DeltaFilter
-DeltaFilter::DeltaFilter(float delta, bool percentage_mode)
-    : delta_(delta), current_delta_(delta), last_value_(NAN), percentage_mode_(percentage_mode) {}
+DeltaFilter::DeltaFilter(float min_a0, float min_a1, float max_a0, float max_a1)
+    : min_a0_(min_a0), min_a1_(min_a1), max_a0_(max_a0), max_a1_(max_a1) {}
+
+void DeltaFilter::set_baseline(float (*fn)(float)) { this->baseline_ = fn; }
+
 optional<float> DeltaFilter::new_value(float value) {
-  if (std::isnan(value)) {
-    if (std::isnan(this->last_value_)) {
-      return {};
-    } else {
-      return this->last_value_ = value;
-    }
+  // Always yield the first value.
+  if (std::isnan(this->last_value_)) {
+    this->last_value_ = value;
+    return value;
   }
-  float diff = fabsf(value - this->last_value_);
-  if (std::isnan(this->last_value_) || (diff > 0.0f && diff >= this->current_delta_)) {
-    if (this->percentage_mode_) {
-      this->current_delta_ = fabsf(value * this->delta_);
-    }
-    return this->last_value_ = value;
+  // calculate min and max using the linear equation
+  float ref = this->baseline_(this->last_value_);
+  float min = fabsf(this->min_a0_ + ref * this->min_a1_);
+  float max = fabsf(this->max_a0_ + ref * this->max_a1_);
+  float delta = fabsf(value - ref);
+  // if there is no reference, e.g. for the first value, just accept this one,
+  // otherwise accept only if within range.
+  if (delta > min && delta <= max) {
+    this->last_value_ = value;
+    return value;
   }
   return {};
 }

esphome/components/sensor/filter.h

@@ -452,15 +452,21 @@ class HeartbeatFilter : public Filter, public Component {
 
 class DeltaFilter : public Filter {
  public:
-  explicit DeltaFilter(float delta, bool percentage_mode);
+  explicit DeltaFilter(float min_a0, float min_a1, float max_a0, float max_a1);
+
+  void set_baseline(float (*fn)(float));
 
   optional<float> new_value(float value) override;
 
  protected:
-  float delta_;
-  float current_delta_;
+  // These values represent linear equations for the min and max values but in practice only one of a0 and a1 will be
+  // non-zero Each limit is calculated as fabs(a0 + value * a1)
+
+  float min_a0_, min_a1_, max_a0_, max_a1_;
+  // default baseline is the previous value
+  float (*baseline_)(float) = [](float last_value) { return last_value; };
+
   float last_value_{NAN};
-  bool percentage_mode_;
 };
 
 class OrFilter : public Filter {

esphome/components/voice_assistant/voice_assistant.h

@@ -83,7 +83,7 @@ struct Timer {
   }
   // Remove before 2026.8.0
   ESPDEPRECATED("Use to_str() instead. Removed in 2026.8.0", "2026.2.0")
-  std::string to_string() const {  // NOLINT
+  std::string to_string() const {
     char buffer[TO_STR_BUFFER_SIZE];
     return this->to_str(buffer);
   }

esphome/components/wifi_info/text_sensor.py

@@ -79,13 +79,17 @@ async def setup_conf(config, key):
 
 async def to_code(config):
     # Request specific WiFi listeners based on which sensors are configured
+    # Each sensor needs its own listener slot - call request for EACH sensor
+
     # SSID and BSSID use WiFiConnectStateListener
-    if CONF_SSID in config or CONF_BSSID in config:
-        wifi.request_wifi_connect_state_listener()
+    for key in (CONF_SSID, CONF_BSSID):
+        if key in config:
+            wifi.request_wifi_connect_state_listener()
 
     # IP address and DNS use WiFiIPStateListener
-    if CONF_IP_ADDRESS in config or CONF_DNS_ADDRESS in config:
-        wifi.request_wifi_ip_state_listener()
+    for key in (CONF_IP_ADDRESS, CONF_DNS_ADDRESS):
+        if key in config:
+            wifi.request_wifi_ip_state_listener()
 
     # Scan results use WiFiScanResultsListener
     if CONF_SCAN_RESULTS in config:

esphome/components/x9c/x9c.cpp

@@ -6,7 +6,7 @@ namespace x9c {
 
 static const char *const TAG = "x9c.output";
 
-void X9cOutput::trim_value(int change_amount) {
+void X9cOutput::trim_value(int32_t change_amount) {
   if (change_amount == 0) {
     return;
   }
@@ -47,17 +47,17 @@ void X9cOutput::setup() {
 
   if (this->initial_value_ <= 0.50) {
     this->trim_value(-101);  // Set min value (beyond 0)
-    this->trim_value(static_cast<uint32_t>(roundf(this->initial_value_ * 100)));
+    this->trim_value(lroundf(this->initial_value_ * 100));
   } else {
     this->trim_value(101);  // Set max value (beyond 100)
-    this->trim_value(static_cast<uint32_t>(roundf(this->initial_value_ * 100) - 100));
+    this->trim_value(lroundf(this->initial_value_ * 100) - 100);
   }
   this->pot_value_ = this->initial_value_;
   this->write_state(this->initial_value_);
 }
 
 void X9cOutput::write_state(float state) {
-  this->trim_value(static_cast<uint32_t>(roundf((state - this->pot_value_) * 100)));
+  this->trim_value(lroundf((state - this->pot_value_) * 100));
   this->pot_value_ = state;
 }
 

esphome/components/x9c/x9c.h

@@ -18,7 +18,7 @@ class X9cOutput : public output::FloatOutput, public Component {
   void setup() override;
   void dump_config() override;
 
-  void trim_value(int change_amount);
+  void trim_value(int32_t change_amount);
 
  protected:
   void write_state(float state) override;

esphome/core/helpers.h

@@ -348,6 +348,8 @@ template<typename T> class FixedVector {
 
   size_t size() const { return size_; }
   bool empty() const { return size_ == 0; }
+  size_t capacity() const { return capacity_; }
+  bool full() const { return size_ == capacity_; }
 
   /// Access element without bounds checking (matches std::vector behavior)
   /// Caller must ensure index is valid (i < size())

script/ci-custom.py

@@ -732,47 +732,6 @@ def lint_no_heap_allocating_helpers(fname, match):
     )
 
 
-@lint_re_check(
-    # Match std::to_string() or unqualified to_string() calls
-    # The esphome namespace has "using std::to_string;" so unqualified calls resolve to std::to_string
-    # Use negative lookbehind to avoid matching:
-    #   - Function definitions: "const char *to_string(" or "std::string to_string("
-    #   - Method definitions: "Class::to_string("
-    #   - Method calls: ".to_string(" or "->to_string("
-    #   - Other identifiers: "_to_string("
-    r"(?<![*&.\w>:])to_string\s*\(" + CPP_RE_EOL,
-    include=cpp_include,
-    exclude=[
-        # Vendored library
-        "esphome/components/http_request/httplib.h",
-        # Deprecated helpers that return std::string
-        "esphome/core/helpers.cpp",
-        # The using declaration itself
-        "esphome/core/helpers.h",
-        # Test fixtures - not production embedded code
-        "tests/integration/fixtures/*",
-    ],
-)
-def lint_no_std_to_string(fname, match):
-    return (
-        f"{highlight('std::to_string()')} allocates heap memory. On long-running embedded "
-        f"devices, repeated heap allocations fragment memory over time.\n"
-        f"Please use {highlight('snprintf()')} with a stack buffer instead.\n"
-        f"\n"
-        f"Buffer sizes and format specifiers:\n"
-        f"  uint8_t/int8_t:   4 chars   - %u / %d (or PRIu8/PRId8)\n"
-        f"  uint16_t/int16_t: 6 chars   - %u / %d (or PRIu16/PRId16)\n"
-        f"  uint32_t/int32_t: 11 chars  - %" + "PRIu32 / %" + "PRId32\n"
-        "  uint64_t/int64_t: 21 chars  - %" + "PRIu64 / %" + "PRId64\n"
-        f"  float/double:     24 chars  - %.8g (15 digits + sign + decimal + e+XXX)\n"
-        f"                    317 chars - %f (for DBL_MAX: 309 int digits + decimal + 6 frac + sign)\n"
-        f"\n"
-        f"For sensor values, use value_accuracy_to_buf() from helpers.h.\n"
-        f'Example: char buf[11]; snprintf(buf, sizeof(buf), "%" PRIu32, value);\n'
-        f"(If strictly necessary, add `{highlight('// NOLINT')}` to the end of the line)"
-    )
-
-
 @lint_content_find_check(
     "ESP_LOG",
     include=["*.h", "*.tcc"],

tests/components/template/common-base.yaml

@@ -121,6 +121,8 @@ sensor:
           min_value: -10.0
       - debounce: 0.1s
       - delta: 5.0
+      - delta:
+          max_value: 2%
       - exponential_moving_average:
           alpha: 0.1
           send_every: 15

tests/integration/fixtures/sensor_filters_delta.yaml

@@ -0,0 +1,180 @@
+esphome:
+  name: test-delta-filters
+
+host:
+api:
+  batch_delay: 0ms  # Disable batching to receive all state updates
+logger:
+  level: DEBUG
+
+sensor:
+  - platform: template
+    name: "Source Sensor 1"
+    id: source_sensor_1
+    accuracy_decimals: 1
+
+  - platform: template
+    name: "Source Sensor 2"
+    id: source_sensor_2
+    accuracy_decimals: 1
+
+  - platform: template
+    name: "Source Sensor 3"
+    id: source_sensor_3
+    accuracy_decimals: 1
+
+  - platform: template
+    name: "Source Sensor 4"
+    id: source_sensor_4
+    accuracy_decimals: 1
+
+  - platform: copy
+    source_id: source_sensor_1
+    name: "Filter Min"
+    id: filter_min
+    filters:
+      - delta:
+          min_value: 10
+
+  - platform: copy
+    source_id: source_sensor_2
+    name: "Filter Max"
+    id: filter_max
+    filters:
+      - delta:
+          max_value: 10
+
+  - platform: copy
+    source_id: source_sensor_3
+    id: test_3_baseline
+    filters:
+      - median:
+          window_size: 6
+          send_every: 1
+          send_first_at: 1
+
+  - platform: copy
+    source_id: source_sensor_3
+    name: "Filter Baseline Max"
+    id: filter_baseline_max
+    filters:
+      - delta:
+          max_value: 10
+          baseline: !lambda return id(test_3_baseline).state;
+
+  - platform: copy
+    source_id: source_sensor_4
+    name: "Filter Zero Delta"
+    id: filter_zero_delta
+    filters:
+      - delta: 0
+
+script:
+  - id: test_filter_min
+    then:
+      - sensor.template.publish:
+          id: source_sensor_1
+          state: 1.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_1
+          state: 5.0  # Filtered out
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_1
+          state: 12.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_1
+          state: 8.0  # Filtered out
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_1
+          state: -2.0
+
+  - id: test_filter_max
+    then:
+      - sensor.template.publish:
+          id: source_sensor_2
+          state: 1.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_2
+          state: 5.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_2
+          state: 40.0  # Filtered out
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_2
+          state: 10.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_2
+          state: -40.0  # Filtered out
+
+  - id: test_filter_baseline_max
+    then:
+      - sensor.template.publish:
+          id: source_sensor_3
+          state: 1.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_3
+          state: 2.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_3
+          state: 3.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_3
+          state: 40.0  # Filtered out
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_3
+          state: 20.0  # Filtered out
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_3
+          state: 20.0
+
+  - id: test_filter_zero_delta
+    then:
+      - sensor.template.publish:
+          id: source_sensor_4
+          state: 1.0
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_4
+          state: 1.0  # Filtered out
+      - delay: 20ms
+      - sensor.template.publish:
+          id: source_sensor_4
+          state: 2.0
+
+button:
+  - platform: template
+    name: "Test Filter Min"
+    id: btn_filter_min
+    on_press:
+      - script.execute: test_filter_min
+
+  - platform: template
+    name: "Test Filter Max"
+    id: btn_filter_max
+    on_press:
+      - script.execute: test_filter_max
+
+  - platform: template
+    name: "Test Filter Baseline Max"
+    id: btn_filter_baseline_max
+    on_press:
+      - script.execute: test_filter_baseline_max
+
+  - platform: template
+    name: "Test Filter Zero Delta"
+    id: btn_filter_zero_delta
+    on_press:
+      - script.execute: test_filter_zero_delta

tests/integration/test_sensor_filters_delta.py

@@ -0,0 +1,163 @@
+"""Test sensor DeltaFilter functionality."""
+
+from __future__ import annotations
+
+import asyncio
+
+from aioesphomeapi import ButtonInfo, EntityState, SensorState
+import pytest
+
+from .state_utils import InitialStateHelper, build_key_to_entity_mapping
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_sensor_filters_delta(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    loop = asyncio.get_running_loop()
+
+    sensor_values: dict[str, list[float]] = {
+        "filter_min": [],
+        "filter_max": [],
+        "filter_baseline_max": [],
+        "filter_zero_delta": [],
+    }
+
+    filter_min_done = loop.create_future()
+    filter_max_done = loop.create_future()
+    filter_baseline_max_done = loop.create_future()
+    filter_zero_delta_done = loop.create_future()
+
+    def on_state(state: EntityState) -> None:
+        if not isinstance(state, SensorState) or state.missing_state:
+            return
+
+        sensor_name = key_to_sensor.get(state.key)
+        if sensor_name not in sensor_values:
+            return
+
+        sensor_values[sensor_name].append(state.state)
+
+        # Check completion conditions
+        if (
+            sensor_name == "filter_min"
+            and len(sensor_values[sensor_name]) == 3
+            and not filter_min_done.done()
+        ):
+            filter_min_done.set_result(True)
+        elif (
+            sensor_name == "filter_max"
+            and len(sensor_values[sensor_name]) == 3
+            and not filter_max_done.done()
+        ):
+            filter_max_done.set_result(True)
+        elif (
+            sensor_name == "filter_baseline_max"
+            and len(sensor_values[sensor_name]) == 4
+            and not filter_baseline_max_done.done()
+        ):
+            filter_baseline_max_done.set_result(True)
+        elif (
+            sensor_name == "filter_zero_delta"
+            and len(sensor_values[sensor_name]) == 2
+            and not filter_zero_delta_done.done()
+        ):
+            filter_zero_delta_done.set_result(True)
+
+    async with (
+        run_compiled(yaml_config),
+        api_client_connected() as client,
+    ):
+        # Get entities and build key mapping
+        entities, _ = await client.list_entities_services()
+        key_to_sensor = build_key_to_entity_mapping(
+            entities,
+            {
+                "filter_min": "Filter Min",
+                "filter_max": "Filter Max",
+                "filter_baseline_max": "Filter Baseline Max",
+                "filter_zero_delta": "Filter Zero Delta",
+            },
+        )
+
+        # Set up initial state helper with all entities
+        initial_state_helper = InitialStateHelper(entities)
+
+        # Subscribe to state changes with wrapper
+        client.subscribe_states(initial_state_helper.on_state_wrapper(on_state))
+
+        # Wait for initial states
+        await initial_state_helper.wait_for_initial_states()
+
+        # Find all buttons
+        button_name_map = {
+            "Test Filter Min": "filter_min",
+            "Test Filter Max": "filter_max",
+            "Test Filter Baseline Max": "filter_baseline_max",
+            "Test Filter Zero Delta": "filter_zero_delta",
+        }
+        buttons = {}
+        for entity in entities:
+            if isinstance(entity, ButtonInfo) and entity.name in button_name_map:
+                buttons[button_name_map[entity.name]] = entity.key
+
+        assert len(buttons) == 4, f"Expected 3 buttons, found {len(buttons)}"
+
+        # Test 1: Min
+        sensor_values["filter_min"].clear()
+        client.button_command(buttons["filter_min"])
+        try:
+            await asyncio.wait_for(filter_min_done, timeout=2.0)
+        except TimeoutError:
+            pytest.fail(f"Test 1 timed out. Values: {sensor_values['filter_min']}")
+
+        expected = [1.0, 12.0, -2.0]
+        assert sensor_values["filter_min"] == pytest.approx(expected), (
+            f"Test 1 failed: expected {expected}, got {sensor_values['filter_min']}"
+        )
+
+        # Test 2: Max
+        sensor_values["filter_max"].clear()
+        client.button_command(buttons["filter_max"])
+        try:
+            await asyncio.wait_for(filter_max_done, timeout=2.0)
+        except TimeoutError:
+            pytest.fail(f"Test 2 timed out. Values: {sensor_values['filter_max']}")
+
+        expected = [1.0, 5.0, 10.0]
+        assert sensor_values["filter_max"] == pytest.approx(expected), (
+            f"Test 2 failed: expected {expected}, got {sensor_values['filter_max']}"
+        )
+
+        # Test 3: Baseline Max
+        sensor_values["filter_baseline_max"].clear()
+        client.button_command(buttons["filter_baseline_max"])
+        try:
+            await asyncio.wait_for(filter_baseline_max_done, timeout=2.0)
+        except TimeoutError:
+            pytest.fail(
+                f"Test 3 timed out. Values: {sensor_values['filter_baseline_max']}"
+            )
+
+        expected = [1.0, 2.0, 3.0, 20.0]
+        assert sensor_values["filter_baseline_max"] == pytest.approx(expected), (
+            f"Test 3 failed: expected {expected}, got {sensor_values['filter_baseline_max']}"
+        )
+
+        # Test 4: Zero Delta
+        sensor_values["filter_zero_delta"].clear()
+        client.button_command(buttons["filter_zero_delta"])
+        try:
+            await asyncio.wait_for(filter_zero_delta_done, timeout=2.0)
+        except TimeoutError:
+            pytest.fail(
+                f"Test 4 timed out. Values: {sensor_values['filter_zero_delta']}"
+            )
+
+        expected = [1.0, 2.0]
+        assert sensor_values["filter_zero_delta"] == pytest.approx(expected), (
+            f"Test 4 failed: expected {expected}, got {sensor_values['filter_zero_delta']}"
+        )