diff --git a/libc/test/src/stdbit/CMakeLists.txt b/libc/test/src/stdbit/CMakeLists.txt
@@ -7,6 +7,7 @@ add_libc_test(
   SRCS
     stdc_leading_zeros_uc_test.cpp
   DEPENDS
+    libc.src.__support.CPP.limits
     libc.src.stdbit.stdc_leading_zeros_uc
 )
 
@@ -17,6 +18,7 @@ add_libc_test(
   SRCS
     stdc_leading_zeros_us_test.cpp
   DEPENDS
+    libc.src.__support.CPP.limits
     libc.src.stdbit.stdc_leading_zeros_us
 )
 
@@ -27,6 +29,7 @@ add_libc_test(
   SRCS
     stdc_leading_zeros_ui_test.cpp
   DEPENDS
+    libc.src.__support.CPP.limits
     libc.src.stdbit.stdc_leading_zeros_ui
 )
 
@@ -37,6 +40,7 @@ add_libc_test(
   SRCS
     stdc_leading_zeros_ul_test.cpp
   DEPENDS
+    libc.src.__support.CPP.limits
     libc.src.stdbit.stdc_leading_zeros_ul
 )
 
@@ -47,5 +51,62 @@ add_libc_test(
   SRCS
     stdc_leading_zeros_ull_test.cpp
   DEPENDS
+    libc.src.__support.CPP.limits
     libc.src.stdbit.stdc_leading_zeros_ull
 )
+
+add_libc_test(
+  stdc_leading_ones_uc_test
+  SUITE
+    libc-stdbit-tests
+  SRCS
+    stdc_leading_ones_uc_test.cpp
+  DEPENDS
+    libc.src.__support.CPP.limits
+    libc.src.stdbit.stdc_leading_ones_uc
+)
+
+add_libc_test(
+  stdc_leading_ones_us_test
+  SUITE
+    libc-stdbit-tests
+  SRCS
+    stdc_leading_ones_us_test.cpp
+  DEPENDS
+    libc.src.__support.CPP.limits
+    libc.src.stdbit.stdc_leading_ones_us
+)
+
+add_libc_test(
+  stdc_leading_ones_ui_test
+  SUITE
+    libc-stdbit-tests
+  SRCS
+    stdc_leading_ones_ui_test.cpp
+  DEPENDS
+    libc.src.__support.CPP.limits
+    libc.src.stdbit.stdc_leading_ones_ui
+)
+
+add_libc_test(
+  stdc_leading_ones_ul_test
+  SUITE
+    libc-stdbit-tests
+  SRCS
+    stdc_leading_ones_ul_test.cpp
+  DEPENDS
+    libc.src.__support.CPP.limits
+    libc.src.stdbit.stdc_leading_ones_ul
+)
+
+add_libc_test(
+  stdc_leading_ones_ull_test
+  SUITE
+    libc-stdbit-tests
+  SRCS
+    stdc_leading_ones_ull_test.cpp
+  DEPENDS
+    libc.src.__support.CPP.limits
+    libc.src.stdbit.stdc_leading_ones_ull
+)
+
diff --git a/libc/test/src/stdbit/stdc_leading_ones_uc_test.cpp b/libc/test/src/stdbit/stdc_leading_ones_uc_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_leading_ones_uc --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/limits.h"
+#include "src/stdbit/stdc_leading_ones_uc.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcLeadingOnesUcTest, All) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_uc(UCHAR_MAX),
+            static_cast<unsigned char>(UCHAR_WIDTH));
+}
+
+TEST(LlvmLibcStdcLeadingOnesUcTest, ZeroHot) {
+  for (unsigned i = 0U; i != UCHAR_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_uc(~(1U << i)),
+              static_cast<unsigned char>(UCHAR_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_leading_ones_ui_test.cpp b/libc/test/src/stdbit/stdc_leading_ones_ui_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_leading_ones_ui --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/limits.h"
+#include "src/stdbit/stdc_leading_ones_ui.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcLeadingOnesUiTest, All) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_ui(UINT_MAX),
+            static_cast<unsigned>(UINT_WIDTH));
+}
+
+TEST(LlvmLibcStdcLeadingOnesUiTest, ZeroHot) {
+  for (unsigned i = 0U; i != UINT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_ui(~(1U << i)),
+              static_cast<unsigned>(UINT_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_leading_ones_ul_test.cpp b/libc/test/src/stdbit/stdc_leading_ones_ul_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_leading_ones_ul --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/limits.h"
+#include "src/stdbit/stdc_leading_ones_ul.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcLeadingOnesUlTest, All) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_ul(ULONG_MAX),
+            static_cast<unsigned long>(ULONG_WIDTH));
+}
+
+TEST(LlvmLibcStdcLeadingOnesUlTest, ZeroHot) {
+  for (unsigned i = 0U; i != ULONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_ul(~(1UL << i)),
+              static_cast<unsigned long>(ULONG_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_leading_ones_ull_test.cpp b/libc/test/src/stdbit/stdc_leading_ones_ull_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_leading_ones_ull -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/limits.h"
+#include "src/stdbit/stdc_leading_ones_ull.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcLeadingOnesUllTest, All) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_ull(ULLONG_MAX),
+            static_cast<unsigned long long>(ULLONG_WIDTH));
+}
+
+TEST(LlvmLibcStdcLeadingOnesUllTest, ZeroHot) {
+  for (unsigned i = 0U; i != ULLONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_ull(~(1ULL << i)),
+              static_cast<unsigned long long>(ULLONG_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_leading_ones_us_test.cpp b/libc/test/src/stdbit/stdc_leading_ones_us_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_leading_ones_us --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/CPP/limits.h"
+#include "src/stdbit/stdc_leading_ones_us.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcLeadingOnesUsTest, All) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_us(USHRT_MAX),
+            static_cast<unsigned short>(USHRT_WIDTH));
+}
+
+TEST(LlvmLibcStdcLeadingOnesUsTest, ZeroHot) {
+  for (unsigned i = 0U; i != USHRT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_leading_ones_us(~(1U << i)),
+              static_cast<unsigned short>(USHRT_WIDTH - i - 1));
+}