From c8e636f25365640d38b67929ff7f5b4bd3cb2bdb Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Wed, 8 Apr 2026 20:51:06 -1000
Subject: [PATCH] Add unit tests for small_pow10, uint32_to_str, frac_to_str

---
 tests/components/core/test_helpers.cpp | 119 +++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 tests/components/core/test_helpers.cpp

diff --git a/tests/components/core/test_helpers.cpp b/tests/components/core/test_helpers.cpp
new file mode 100644
index 0000000000..50df1492ad
--- /dev/null
+++ b/tests/components/core/test_helpers.cpp
@@ -0,0 +1,119 @@
+#include <gtest/gtest.h>
+#include <cstring>
+
+#include "esphome/core/helpers.h"
+
+namespace esphome::testing {
+
+// --- 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); }
+
+// --- uint32_to_str() ---
+
+TEST(Uint32ToStr, Zero) {
+  char buf[12];
+  char *end = uint32_to_str(buf, 0);
+  *end = '\0';
+  EXPECT_STREQ(buf, "0");
+  EXPECT_EQ(end - buf, 1);
+}
+
+TEST(Uint32ToStr, SingleDigit) {
+  char buf[12];
+  char *end = uint32_to_str(buf, 7);
+  *end = '\0';
+  EXPECT_STREQ(buf, "7");
+}
+
+TEST(Uint32ToStr, MultiDigit) {
+  char buf[12];
+  char *end = uint32_to_str(buf, 12345);
+  *end = '\0';
+  EXPECT_STREQ(buf, "12345");
+  EXPECT_EQ(end - buf, 5);
+}
+
+TEST(Uint32ToStr, Large) {
+  char buf[12];
+  char *end = uint32_to_str(buf, 4294967295u);
+  *end = '\0';
+  EXPECT_STREQ(buf, "4294967295");
+  EXPECT_EQ(end - buf, 10);
+}
+
+TEST(Uint32ToStr, PowersOfTen) {
+  char buf[12];
+  char *end;
+
+  end = uint32_to_str(buf, 10);
+  *end = '\0';
+  EXPECT_STREQ(buf, "10");
+
+  end = uint32_to_str(buf, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "100");
+
+  end = uint32_to_str(buf, 1000);
+  *end = '\0';
+  EXPECT_STREQ(buf, "1000");
+}
+
+// --- frac_to_str() ---
+
+TEST(FracToStr, OneDigit) {
+  char buf[8];
+  char *end = frac_to_str(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(buf, 46, 10);
+  *end = '\0';
+  EXPECT_STREQ(buf, "46");
+}
+
+TEST(FracToStr, ThreeDigits) {
+  char buf[8];
+  char *end = frac_to_str(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(buf, 1, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "001");
+
+  end = frac_to_str(buf, 5, 10);
+  *end = '\0';
+  EXPECT_STREQ(buf, "05");
+}
+
+TEST(FracToStr, AllZeros) {
+  char buf[8];
+  char *end = frac_to_str(buf, 0, 100);
+  *end = '\0';
+  EXPECT_STREQ(buf, "000");
+
+  end = frac_to_str(buf, 0, 1);
+  *end = '\0';
+  EXPECT_STREQ(buf, "0");
+}
+
+TEST(FracToStr, ZeroDivisor) {
+  char buf[8];
+  buf[0] = 'X';
+  char *end = frac_to_str(buf, 0, 0);
+  EXPECT_EQ(end, buf);  // writes nothing
+}
+
+}  // namespace esphome::testing