Merge remote-tracking branch 'origin/optimize-value-accuracy' into integration

# Conflicts:
#	esphome/core/application.cpp
#	esphome/core/application.h
#	tests/components/core/test_helpers.cpp

esphome/components/audio/__init__.py

@@ -1,7 +1,11 @@
 from dataclasses import dataclass
 
 import esphome.codegen as cg
-from esphome.components.esp32 import add_idf_component, include_builtin_idf_component
+from esphome.components.esp32 import (
+    add_idf_component,
+    add_idf_sdkconfig_option,
+    include_builtin_idf_component,
+)
 import esphome.config_validation as cv
 from esphome.const import CONF_BITS_PER_SAMPLE, CONF_NUM_CHANNELS, CONF_SAMPLE_RATE
 from esphome.core import CORE
@@ -27,6 +31,7 @@ class AudioData:
     flac_support: bool = False
     mp3_support: bool = False
     opus_support: bool = False
+    micro_decoder_support: bool = False
 
 
 def _get_data() -> AudioData:
@@ -50,6 +55,11 @@ def request_opus_support() -> None:
     _get_data().opus_support = True
 
 
+def request_micro_decoder_support() -> None:
+    """Request micro-decoder library support for audio decoding."""
+    _get_data().micro_decoder_support = True
+
+
 CONF_MIN_BITS_PER_SAMPLE = "min_bits_per_sample"
 CONF_MAX_BITS_PER_SAMPLE = "max_bits_per_sample"
 CONF_MIN_CHANNELS = "min_channels"
@@ -208,6 +218,19 @@ async def to_code(config):
     )
 
     data = _get_data()
+
+    if data.micro_decoder_support:
+        add_idf_component(name="esphome/micro-decoder", ref="0.1.1")
+
+        # All codecs are enabled by default in micro-decoder, so disable the ones that aren't requested to save flash
+        if not data.flac_support:
+            add_idf_sdkconfig_option("CONFIG_MICRO_DECODER_CODEC_FLAC", False)
+        if not data.mp3_support:
+            add_idf_sdkconfig_option("CONFIG_MICRO_DECODER_CODEC_MP3", False)
+        if not data.opus_support:
+            add_idf_sdkconfig_option("CONFIG_MICRO_DECODER_CODEC_OPUS", False)
+
+    # Legacy audio_decoder.cpp support defines and components
     if data.flac_support:
         cg.add_define("USE_AUDIO_FLAC_SUPPORT")
         add_idf_component(name="esphome/micro-flac", ref="0.1.1")

esphome/components/esp32/preferences.cpp

@@ -4,7 +4,6 @@
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <nvs_flash.h>
-#include <cinttypes>
 #include <cstring>
 #include <vector>
 
@@ -12,9 +11,6 @@ namespace esphome::esp32 {
 
 static const char *const TAG = "preferences";
 
-// Buffer size for converting uint32_t to string: max "4294967295" (10 chars) + null terminator + 1 padding
-static constexpr size_t KEY_BUFFER_SIZE = 12;
-
 struct NVSData {
   uint32_t key;
   SmallInlineBuffer<8> data;  // Most prefs fit in 8 bytes (covers fan, cover, select, etc.)
@@ -51,8 +47,8 @@ bool ESP32PreferenceBackend::load(uint8_t *data, size_t len) {
     }
   }
 
-  char key_str[KEY_BUFFER_SIZE];
-  snprintf(key_str, sizeof(key_str), "%" PRIu32, this->key);
+  char key_str[UINT32_MAX_STR_SIZE];
+  uint32_to_str(key_str, this->key);
   size_t actual_len;
   esp_err_t err = nvs_get_blob(this->nvs_handle, key_str, nullptr, &actual_len);
   if (err != 0) {
@@ -108,8 +104,8 @@ bool ESP32Preferences::sync() {
   uint32_t last_key = 0;
 
   for (const auto &save : s_pending_save) {
-    char key_str[KEY_BUFFER_SIZE];
-    snprintf(key_str, sizeof(key_str), "%" PRIu32, save.key);
+    char key_str[UINT32_MAX_STR_SIZE];
+    uint32_to_str(key_str, save.key);
     ESP_LOGVV(TAG, "Checking if NVS data %s has changed", key_str);
     if (this->is_changed_(this->nvs_handle, save, key_str)) {
       esp_err_t err = nvs_set_blob(this->nvs_handle, key_str, save.data.data(), save.data.size());

esphome/components/libretiny/preferences.cpp

@@ -3,7 +3,6 @@
 #include "preferences.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
-#include <cinttypes>
 #include <cstring>
 #include <vector>
 
@@ -11,9 +10,6 @@ namespace esphome::libretiny {
 
 static const char *const TAG = "preferences";
 
-// Buffer size for converting uint32_t to string: max "4294967295" (10 chars) + null terminator + 1 padding
-static constexpr size_t KEY_BUFFER_SIZE = 12;
-
 struct NVSData {
   uint32_t key;
   SmallInlineBuffer<8> data;  // Most prefs fit in 8 bytes (covers fan, cover, select, etc.)
@@ -50,8 +46,8 @@ bool LibreTinyPreferenceBackend::load(uint8_t *data, size_t len) {
     }
   }
 
-  char key_str[KEY_BUFFER_SIZE];
-  snprintf(key_str, sizeof(key_str), "%" PRIu32, this->key);
+  char key_str[UINT32_MAX_STR_SIZE];
+  uint32_to_str(key_str, this->key);
   fdb_blob_make(this->blob, data, len);
   size_t actual_len = fdb_kv_get_blob(this->db, key_str, this->blob);
   if (actual_len != len) {
@@ -92,8 +88,8 @@ bool LibreTinyPreferences::sync() {
   uint32_t last_key = 0;
 
   for (const auto &save : s_pending_save) {
-    char key_str[KEY_BUFFER_SIZE];
-    snprintf(key_str, sizeof(key_str), "%" PRIu32, save.key);
+    char key_str[UINT32_MAX_STR_SIZE];
+    uint32_to_str(key_str, save.key);
     ESP_LOGVV(TAG, "Checking if FDB data %s has changed", key_str);
     if (this->is_changed_(&this->db, save, key_str)) {
       ESP_LOGV(TAG, "sync: key: %s, len: %zu", key_str, save.data.size());

esphome/core/helpers.cpp

@@ -380,6 +380,20 @@ static char *format_hex_internal(char *buffer, size_t buffer_size, const uint8_t
   return buffer;
 }
 
+char *uint32_to_str_unchecked(char *buf, uint32_t val) {
+  if (val == 0) {
+    *buf++ = '0';
+    return buf;
+  }
+  char *start = buf;
+  while (val > 0) {
+    *buf++ = '0' + (val % 10);
+    val /= 10;
+  }
+  std::reverse(start, buf);
+  return buf;
+}
+
 char *format_hex_to(char *buffer, size_t buffer_size, const uint8_t *data, size_t length) {
   return format_hex_internal(buffer, buffer_size, data, length, 0, 'a');
 }
@@ -529,28 +543,58 @@ std::string value_accuracy_to_string(float value, int8_t accuracy_decimals) {
   return std::string(buf);
 }
 
+// Fast float-to-string for accuracy_decimals 0-3 (covers virtually all sensor usage).
+// Avoids snprintf("%.*f") which pulls in heavy float formatting machinery.
+// Caller must guarantee value is finite and |value| * mult fits in uint32_t.
+static size_t value_accuracy_to_buf_fast(char *buf, float value, int8_t accuracy_decimals, uint32_t mult) {
+  char *p = buf;
+  if (std::signbit(value)) {
+    *p++ = '-';
+    value = -value;
+  }
+  // Cast to double for the multiply to match snprintf's rounding precision.
+  // float*int loses bits at exact-half boundaries (e.g. 23.45f*10 = 234.5 in float,
+  // but snprintf sees 234.500007... via double promotion and rounds differently).
+  // llrint returns long long so the result fits even on 32-bit targets where
+  // long is 32-bit; caller has already bounded |value * mult| to UINT32_MAX.
+  uint32_t scaled = static_cast<uint32_t>(llrint(static_cast<double>(value) * mult));
+  p = uint32_to_str_unchecked(p, scaled / mult);
+  if (accuracy_decimals > 0) {
+    *p++ = '.';
+    p = frac_to_str_unchecked(p, scaled % mult, mult / 10);
+  }
+  *p = '\0';
+  return static_cast<size_t>(p - buf);
+}
+
 size_t value_accuracy_to_buf(std::span<char, VALUE_ACCURACY_MAX_LEN> buf, float value, int8_t accuracy_decimals) {
   normalize_accuracy_decimals(value, accuracy_decimals);
-  // snprintf returns chars that would be written (excluding null), or negative on error
+
+  // Fast path for accuracy 0-3, finite values whose scaled magnitude fits in uint32_t.
+  // For 3 decimals that's |value| < ~4.29e6; larger totals fall through to snprintf.
+  if (accuracy_decimals <= 3 && std::isfinite(value)) {
+    const uint32_t mult = small_pow10(accuracy_decimals);
+    if (std::fabs(value) < static_cast<float>(UINT32_MAX) / mult) {
+      return value_accuracy_to_buf_fast(buf.data(), value, accuracy_decimals, mult);
+    }
+  }
+
+  // Fallback for NaN/Inf/high accuracy/out-of-range
   int len = snprintf(buf.data(), buf.size(), "%.*f", accuracy_decimals, value);
   if (len < 0)
-    return 0;  // encoding error
-  // On truncation, snprintf returns would-be length; actual written is buf.size() - 1
+    return 0;
   return static_cast<size_t>(len) >= buf.size() ? buf.size() - 1 : static_cast<size_t>(len);
 }
 
 size_t value_accuracy_with_uom_to_buf(std::span<char, VALUE_ACCURACY_MAX_LEN> buf, float value,
                                       int8_t accuracy_decimals, StringRef unit_of_measurement) {
-  if (unit_of_measurement.empty()) {
-    return value_accuracy_to_buf(buf, value, accuracy_decimals);
+  size_t len = value_accuracy_to_buf(buf, value, accuracy_decimals);
+  if (len == 0 || unit_of_measurement.empty()) {
+    return len;
   }
-  normalize_accuracy_decimals(value, accuracy_decimals);
-  // snprintf returns chars that would be written (excluding null), or negative on error
-  int len = snprintf(buf.data(), buf.size(), "%.*f %s", accuracy_decimals, value, unit_of_measurement.c_str());
-  if (len < 0)
-    return 0;  // encoding error
-  // On truncation, snprintf returns would-be length; actual written is buf.size() - 1
-  return static_cast<size_t>(len) >= buf.size() ? buf.size() - 1 : static_cast<size_t>(len);
+  char *end = buf_append_sep_str(buf.data() + len, buf.size() - len, ' ', unit_of_measurement.c_str(),
+                                 unit_of_measurement.size());
+  return static_cast<size_t>(end - buf.data());
 }
 
 int8_t step_to_accuracy_decimals(float step) {

esphome/core/helpers.h

@@ -1295,6 +1295,56 @@ inline char *int8_to_str(char *buf, int8_t val) {
   return buf;
 }
 
+/// Append a separator char and a string to a buffer, respecting remaining space.
+/// Returns pointer past last char written. The buffer is always null-terminated
+/// when remaining >= 1 (even on the no-room early-return), so callers always get
+/// a valid C string.
+inline char *buf_append_sep_str(char *buf, size_t remaining, char separator, const char *str, size_t str_len) {
+  if (remaining < 2) {
+    if (remaining >= 1) {
+      *buf = '\0';
+    }
+    return buf;
+  }
+  *buf++ = separator;
+  remaining--;
+  size_t copy_len = std::min(str_len, remaining - 1);
+  memcpy(buf, str, copy_len);
+  buf += copy_len;
+  *buf = '\0';
+  return buf;
+}
+
+/// Return 10^n for small non-negative n (0-3) as uint32_t, avoiding float.
+inline uint32_t small_pow10(int8_t n) { return n == 3 ? 1000 : n == 2 ? 100 : n == 1 ? 10 : 1; }
+
+/// Minimum buffer size for uint32_to_str: 10 digits + null terminator.
+static constexpr size_t UINT32_MAX_STR_SIZE = 11;
+
+/// Write unsigned 32-bit integer to buffer (internal, no size check).
+/// Buffer must have at least 10 bytes free. Returns pointer past last char written.
+char *uint32_to_str_unchecked(char *buf, uint32_t val);
+
+/// Write unsigned 32-bit integer to buffer with compile-time size check.
+/// Null-terminates the output. Returns number of chars written (excluding null).
+inline size_t uint32_to_str(std::span<char, UINT32_MAX_STR_SIZE> buf, uint32_t val) {
+  char *end = uint32_to_str_unchecked(buf.data(), val);
+  *end = '\0';
+  return static_cast<size_t>(end - buf.data());
+}
+
+/// Write fractional digits with leading zeros to buffer (internal, no size check).
+/// frac is the fractional value, divisor is the highest place value (e.g. 100 for 3 digits).
+/// Returns pointer past last char written.
+inline char *frac_to_str_unchecked(char *buf, uint32_t frac, uint32_t divisor) {
+  while (divisor > 0) {
+    *buf++ = '0' + static_cast<char>(frac / divisor);
+    frac %= divisor;
+    divisor /= 10;
+  }
+  return buf;
+}
+
 /// Format byte array as lowercase hex to buffer (base implementation).
 char *format_hex_to(char *buffer, size_t buffer_size, const uint8_t *data, size_t length);
 

esphome/idf_component.yml

@@ -3,6 +3,8 @@ dependencies:
     version: "7.4.2"
   esphome/esp-audio-libs:
     version: 2.0.4
+  esphome/micro-decoder:
+    version: 0.1.1
   esphome/micro-flac:
     version: 0.1.1
   esphome/micro-opus:

tests/benchmarks/core/bench_helpers.cpp

@@ -1,4 +1,6 @@
 #include <benchmark/benchmark.h>
+#include <cinttypes>
+#include <cstdio>
 
 #include "esphome/core/helpers.h"
 
@@ -307,4 +309,58 @@ static void Base64Decode_32Bytes(benchmark::State &state) {
 }
 BENCHMARK(Base64Decode_32Bytes);
 
+// --- uint32_to_str() vs snprintf ---
+
+static void Uint32ToStr_Small(benchmark::State &state) {
+  char buf[UINT32_MAX_STR_SIZE];
+  for (auto _ : state) {
+    for (int i = 0; i < kInnerIterations; i++) {
+      uint32_to_str(buf, 12345);
+      benchmark::DoNotOptimize(buf);
+      benchmark::ClobberMemory();
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Uint32ToStr_Small);
+
+static void Snprintf_Uint32_Small(benchmark::State &state) {
+  char buf[UINT32_MAX_STR_SIZE];
+  for (auto _ : state) {
+    for (int i = 0; i < kInnerIterations; i++) {
+      snprintf(buf, sizeof(buf), "%" PRIu32, static_cast<uint32_t>(12345));
+      benchmark::DoNotOptimize(buf);
+      benchmark::ClobberMemory();
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Snprintf_Uint32_Small);
+
+static void Uint32ToStr_Large(benchmark::State &state) {
+  char buf[UINT32_MAX_STR_SIZE];
+  for (auto _ : state) {
+    for (int i = 0; i < kInnerIterations; i++) {
+      uint32_to_str(buf, 4294967295u);
+      benchmark::DoNotOptimize(buf);
+      benchmark::ClobberMemory();
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Uint32ToStr_Large);
+
+static void Snprintf_Uint32_Large(benchmark::State &state) {
+  char buf[UINT32_MAX_STR_SIZE];
+  for (auto _ : state) {
+    for (int i = 0; i < kInnerIterations; i++) {
+      snprintf(buf, sizeof(buf), "%" PRIu32, static_cast<uint32_t>(4294967295u));
+      benchmark::DoNotOptimize(buf);
+      benchmark::ClobberMemory();
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+}
+BENCHMARK(Snprintf_Uint32_Large);
+
 }  // namespace esphome::benchmarks

tests/components/core/test_helpers.cpp

@@ -117,4 +117,100 @@ TEST(FormatHexChar, UppercaseDigits) {
   EXPECT_EQ(format_hex_pretty_char(15), 'F');
 }
 
+// --- small_pow10() ---
+
+TEST(SmallPow10, Zero) { EXPECT_EQ(small_pow10(0), 1u); }
+TEST(SmallPow10, One) { EXPECT_EQ(small_pow10(1), 10u); }
+TEST(SmallPow10, Two) { EXPECT_EQ(small_pow10(2), 100u); }
+TEST(SmallPow10, Three) { EXPECT_EQ(small_pow10(3), 1000u); }
+
+// --- frac_to_str_unchecked() ---
+
+TEST(FracToStr, OneDigit) {
+  char buf[8];
+  char *end = frac_to_str_unchecked(buf, 5, 1);
+  *end = '\0';
+  EXPECT_STREQ(buf, "5");
+  EXPECT_EQ(end - buf, 1);
+}
+
+TEST(FracToStr, TwoDigits) {
+  char buf[8];
+  char *end = frac_to_str_unchecked(buf, 46, 10);
+  *end = '\0';
+  EXPECT_STREQ(buf, "46");
+}
+
+TEST(FracToStr, ThreeDigits) {
+  char buf[8];
+  char *end = frac_to_str_unchecked(buf, 456, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "456");
+  EXPECT_EQ(end - buf, 3);
+}
+
+TEST(FracToStr, LeadingZeros) {
+  char buf[8];
+  char *end = frac_to_str_unchecked(buf, 1, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "001");
+
+  end = frac_to_str_unchecked(buf, 5, 10);
+  *end = '\0';
+  EXPECT_STREQ(buf, "05");
+}
+
+TEST(FracToStr, AllZeros) {
+  char buf[8];
+  char *end = frac_to_str_unchecked(buf, 0, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "000");
+
+  end = frac_to_str_unchecked(buf, 0, 1);
+  *end = '\0';
+  EXPECT_STREQ(buf, "0");
+}
+
+TEST(FracToStr, ZeroDivisor) {
+  char buf[8];
+  buf[0] = 'X';
+  char *end = frac_to_str_unchecked(buf, 0, 0);
+  EXPECT_EQ(end, buf);  // writes nothing
+}
+
+// --- buf_append_sep_str() ---
+
+TEST(BufAppendSepStr, Basic) {
+  char buf[32] = "23.46";
+  char *start = buf + 5;
+  char *end = buf_append_sep_str(start, sizeof(buf) - 5, ' ', "°C", 3);
+  EXPECT_STREQ(buf, "23.46 °C");
+  EXPECT_EQ(end - buf, 9);  // "°C" is 3 bytes (UTF-8)
+}
+
+TEST(BufAppendSepStr, EmptyString) {
+  char buf[32] = "100";
+  char *start = buf + 3;
+  char *end = buf_append_sep_str(start, sizeof(buf) - 3, ' ', "", 0);
+  EXPECT_STREQ(buf, "100 ");
+  EXPECT_EQ(end - start, 1);  // just the separator
+}
+
+TEST(BufAppendSepStr, NoRoom) {
+  char buf[8] = "1234567";
+  char *start = buf + 7;
+  char *end = buf_append_sep_str(start, 1, ' ', "unit", 4);
+  EXPECT_EQ(end, start);  // nothing written
+}
+
+TEST(BufAppendSepStr, Truncation) {
+  char buf[8] = "val";
+  char *start = buf + 3;
+  // remaining = 5, separator takes 1, so 3 chars of string fit + null
+  char *end = buf_append_sep_str(start, 5, ' ', "longunit", 8);
+  *end = '\0';
+  EXPECT_STREQ(buf, "val lon");
+  EXPECT_EQ(end - buf, 7);
+}
+
 }  // namespace esphome::core::testing

tests/components/core/test_uint32_to_str.cpp

@@ -0,0 +1,77 @@
+#include <gtest/gtest.h>
+
+#include "esphome/core/helpers.h"
+
+namespace esphome::core::testing {
+
+// --- uint32_to_str_unchecked() (internal, raw pointer) ---
+
+TEST(Uint32ToStr, InternalZero) {
+  char buf[UINT32_MAX_STR_SIZE];
+  char *end = uint32_to_str_unchecked(buf, 0);
+  *end = '\0';
+  EXPECT_STREQ(buf, "0");
+  EXPECT_EQ(end - buf, 1);
+}
+
+TEST(Uint32ToStr, InternalSingleDigit) {
+  char buf[UINT32_MAX_STR_SIZE];
+  char *end = uint32_to_str_unchecked(buf, 7);
+  *end = '\0';
+  EXPECT_STREQ(buf, "7");
+}
+
+TEST(Uint32ToStr, InternalMultiDigit) {
+  char buf[UINT32_MAX_STR_SIZE];
+  char *end = uint32_to_str_unchecked(buf, 12345);
+  *end = '\0';
+  EXPECT_STREQ(buf, "12345");
+  EXPECT_EQ(end - buf, 5);
+}
+
+TEST(Uint32ToStr, InternalMaxValue) {
+  char buf[UINT32_MAX_STR_SIZE];
+  char *end = uint32_to_str_unchecked(buf, 4294967295u);
+  *end = '\0';
+  EXPECT_STREQ(buf, "4294967295");
+  EXPECT_EQ(end - buf, 10);
+}
+
+TEST(Uint32ToStr, InternalPowersOfTen) {
+  char buf[UINT32_MAX_STR_SIZE];
+  char *end;
+
+  end = uint32_to_str_unchecked(buf, 10);
+  *end = '\0';
+  EXPECT_STREQ(buf, "10");
+
+  end = uint32_to_str_unchecked(buf, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "100");
+
+  end = uint32_to_str_unchecked(buf, 1000000);
+  *end = '\0';
+  EXPECT_STREQ(buf, "1000000");
+}
+
+// --- uint32_to_str() (public, span API) ---
+
+TEST(Uint32ToStr, SpanZero) {
+  char buf[UINT32_MAX_STR_SIZE];
+  EXPECT_EQ(uint32_to_str(buf, 0), 1u);
+  EXPECT_STREQ(buf, "0");
+}
+
+TEST(Uint32ToStr, SpanMultiDigit) {
+  char buf[UINT32_MAX_STR_SIZE];
+  EXPECT_EQ(uint32_to_str(buf, 12345), 5u);
+  EXPECT_STREQ(buf, "12345");
+}
+
+TEST(Uint32ToStr, SpanMaxValue) {
+  char buf[UINT32_MAX_STR_SIZE];
+  EXPECT_EQ(uint32_to_str(buf, 4294967295u), 10u);
+  EXPECT_STREQ(buf, "4294967295");
+}
+
+}  // namespace esphome::core::testing

tests/components/core/test_value_accuracy.cpp

@@ -0,0 +1,152 @@
+#include <gtest/gtest.h>
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+#include <span>
+#include <string>
+
+#include "esphome/core/helpers.h"
+
+namespace esphome::core::testing {
+
+// Helper to call value_accuracy_to_buf and return as string
+static std::string va_to_string(float value, int8_t accuracy_decimals) {
+  char buf[VALUE_ACCURACY_MAX_LEN];
+  std::span<char, VALUE_ACCURACY_MAX_LEN> sp(buf);
+  size_t len = value_accuracy_to_buf(sp, value, accuracy_decimals);
+  return std::string(buf, len);
+}
+
+// Helper: reference implementation using snprintf for comparison
+static std::string va_reference(float value, int8_t accuracy_decimals) {
+  // Replicate normalize_accuracy_decimals logic
+  if (accuracy_decimals < 0) {
+    float divisor;
+    if (accuracy_decimals == -1) {
+      divisor = 10.0f;
+    } else if (accuracy_decimals == -2) {
+      divisor = 100.0f;
+    } else {
+      divisor = pow10_int(-accuracy_decimals);
+    }
+    value = roundf(value / divisor) * divisor;
+    accuracy_decimals = 0;
+  }
+  char buf[VALUE_ACCURACY_MAX_LEN];
+  snprintf(buf, sizeof(buf), "%.*f", accuracy_decimals, value);
+  return std::string(buf);
+}
+
+// --- Basic formatting ---
+
+TEST(ValueAccuracyToBuf, ZeroDecimals) {
+  EXPECT_EQ(va_to_string(23.456f, 0), "23");
+  EXPECT_EQ(va_to_string(0.0f, 0), "0");
+  EXPECT_EQ(va_to_string(100.0f, 0), "100");
+  EXPECT_EQ(va_to_string(1.0f, 0), "1");
+}
+
+TEST(ValueAccuracyToBuf, OneDecimal) {
+  EXPECT_EQ(va_to_string(23.456f, 1), "23.5");
+  EXPECT_EQ(va_to_string(0.0f, 1), "0.0");
+  EXPECT_EQ(va_to_string(1.05f, 1), va_reference(1.05f, 1));
+}
+
+TEST(ValueAccuracyToBuf, TwoDecimals) {
+  EXPECT_EQ(va_to_string(23.456f, 2), "23.46");
+  EXPECT_EQ(va_to_string(0.0f, 2), "0.00");
+  EXPECT_EQ(va_to_string(1.005f, 2), va_reference(1.005f, 2));
+}
+
+TEST(ValueAccuracyToBuf, ThreeDecimals) {
+  EXPECT_EQ(va_to_string(23.456f, 3), "23.456");
+  EXPECT_EQ(va_to_string(0.0f, 3), "0.000");
+}
+
+// --- Negative values ---
+
+TEST(ValueAccuracyToBuf, NegativeValues) {
+  EXPECT_EQ(va_to_string(-23.456f, 2), "-23.46");
+  EXPECT_EQ(va_to_string(-0.5f, 1), "-0.5");
+  EXPECT_EQ(va_to_string(-100.0f, 0), "-100");
+}
+
+// --- Negative accuracy_decimals (rounding to tens/hundreds) ---
+
+TEST(ValueAccuracyToBuf, NegativeAccuracy) {
+  EXPECT_EQ(va_to_string(1234.0f, -1), va_reference(1234.0f, -1));
+  EXPECT_EQ(va_to_string(1234.0f, -2), va_reference(1234.0f, -2));
+  EXPECT_EQ(va_to_string(56.0f, -1), va_reference(56.0f, -1));
+}
+
+// --- Special float values ---
+
+TEST(ValueAccuracyToBuf, NaN) {
+  std::string result = va_to_string(NAN, 2);
+  EXPECT_EQ(result, va_reference(NAN, 2));
+}
+
+TEST(ValueAccuracyToBuf, Infinity) {
+  std::string result = va_to_string(INFINITY, 2);
+  EXPECT_EQ(result, va_reference(INFINITY, 2));
+}
+
+TEST(ValueAccuracyToBuf, NegativeInfinity) {
+  std::string result = va_to_string(-INFINITY, 2);
+  EXPECT_EQ(result, va_reference(-INFINITY, 2));
+}
+
+// --- Edge cases ---
+
+TEST(ValueAccuracyToBuf, VerySmallValues) {
+  EXPECT_EQ(va_to_string(0.001f, 3), "0.001");
+  EXPECT_EQ(va_to_string(0.001f, 2), "0.00");
+  EXPECT_EQ(va_to_string(0.009f, 2), "0.01");
+}
+
+TEST(ValueAccuracyToBuf, LargeValues) {
+  EXPECT_EQ(va_to_string(999999.0f, 0), va_reference(999999.0f, 0));
+  EXPECT_EQ(va_to_string(1013.25f, 2), "1013.25");
+}
+
+TEST(ValueAccuracyToBuf, Rounding) {
+  // 0.5 rounds up
+  EXPECT_EQ(va_to_string(23.5f, 0), "24");
+  EXPECT_EQ(va_to_string(23.45f, 1), "23.5");  // float: 23.45 -> 23.4 or 23.5
+  EXPECT_EQ(va_to_string(23.45f, 1), va_reference(23.45f, 1));
+}
+
+// --- Match snprintf for a range of typical sensor values ---
+
+TEST(ValueAccuracyToBuf, MatchesSnprintf) {
+  float test_values[] = {0.0f, 1.0f, -1.0f, 23.456f, -23.456f, 100.0f, 0.1f, 0.01f, 99.99f, 1013.25f, -40.0f};
+  int8_t test_accuracies[] = {0, 1, 2, 3};
+
+  for (float value : test_values) {
+    for (int8_t acc : test_accuracies) {
+      EXPECT_EQ(va_to_string(value, acc), va_reference(value, acc))
+          << "Mismatch for value=" << value << " accuracy=" << static_cast<int>(acc);
+    }
+  }
+}
+
+// --- Return value (length) ---
+
+TEST(ValueAccuracyToBuf, ReturnsCorrectLength) {
+  char buf[VALUE_ACCURACY_MAX_LEN];
+  std::span<char, VALUE_ACCURACY_MAX_LEN> sp(buf);
+
+  size_t len = value_accuracy_to_buf(sp, 23.456f, 2);
+  EXPECT_EQ(len, 5u);  // "23.46"
+  EXPECT_EQ(strlen(buf), len);
+
+  len = value_accuracy_to_buf(sp, 0.0f, 0);
+  EXPECT_EQ(len, 1u);  // "0"
+  EXPECT_EQ(strlen(buf), len);
+
+  len = value_accuracy_to_buf(sp, -100.0f, 1);
+  EXPECT_EQ(len, 6u);  // "-100.0"
+  EXPECT_EQ(strlen(buf), len);
+}
+
+}  // namespace esphome::core::testing