diff --git a/libc/test/src/stdbit/stdc_bit_ceil_ui_test.cpp b/libc/test/src/stdbit/stdc_bit_ceil_ui_test.cpp
@@ -0,0 +1,30 @@
+//===-- Unittests for stdc_bit_ceil_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_bit_ceil_ui.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitceilUiTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ui(0U), 1U);
+}
+
+TEST(LlvmLibcStdcBitceilUiTest, Ones) {
+  for (unsigned i = 0U; i != UINT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ui(1U << i), 1U << i);
+}
+
+TEST(LlvmLibcStdcBitceilUiTest, OneLessThanPowsTwo) {
+  for (unsigned i = 2U; i != UINT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ui((1U << i) - 1), 1U << i);
+}
+
+TEST(LlvmLibcStdcBitceilUiTest, OneMoreThanPowsTwo) {
+  for (unsigned i = 1U; i != UINT_WIDTH - 1; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ui((1U << i) + 1), 1U << (i + 1));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_ceil_ul_test.cpp b/libc/test/src/stdbit/stdc_bit_ceil_ul_test.cpp
@@ -0,0 +1,30 @@
+//===-- Unittests for stdc_bit_ceil_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_bit_ceil_ul.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitceilUlTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ul(0UL), 1UL);
+}
+
+TEST(LlvmLibcStdcBitceilUlTest, Ones) {
+  for (unsigned i = 0U; i != ULONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ul(1UL << i), 1UL << i);
+}
+
+TEST(LlvmLibcStdcBitceilUlTest, OneLessThanPowsTwo) {
+  for (unsigned i = 2U; i != ULONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ul((1UL << i) - 1), 1UL << i);
+}
+
+TEST(LlvmLibcStdcBitceilUlTest, OneMoreThanPowsTwo) {
+  for (unsigned i = 1U; i != ULONG_WIDTH - 1; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ul((1UL << i) + 1), 1UL << (i + 1));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_ceil_ull_test.cpp b/libc/test/src/stdbit/stdc_bit_ceil_ull_test.cpp
@@ -0,0 +1,31 @@
+//===-- Unittests for stdc_bit_ceil_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_bit_ceil_ull.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitceilUllTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ull(0ULL), 1ULL);
+}
+
+TEST(LlvmLibcStdcBitceilUllTest, Ones) {
+  for (unsigned i = 0U; i != ULLONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ull(1ULL << i), 1ULL << i);
+}
+
+TEST(LlvmLibcStdcBitceilUllTest, OneLessThanPowsTwo) {
+  for (unsigned i = 2U; i != ULLONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ull((1ULL << i) - 1), 1ULL << i);
+}
+
+TEST(LlvmLibcStdcBitceilUllTest, OneMoreThanPowsTwo) {
+  for (unsigned i = 1U; i != ULLONG_WIDTH - 1; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_ull((1ULL << i) + 1),
+              1ULL << (i + 1));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_ceil_us_test.cpp b/libc/test/src/stdbit/stdc_bit_ceil_us_test.cpp
@@ -0,0 +1,34 @@
+//===-- Unittests for stdc_bit_ceil_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_bit_ceil_us.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitceilUsTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_us(0U),
+            static_cast<unsigned short>(1));
+}
+
+TEST(LlvmLibcStdcBitceilUsTest, Ones) {
+  for (unsigned i = 0U; i != USHRT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_us(1U << i),
+              static_cast<unsigned short>(1U << i));
+}
+
+TEST(LlvmLibcStdcBitceilUsTest, OneLessThanPowsTwo) {
+  for (unsigned i = 2U; i != USHRT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_us((1U << i) - 1),
+              static_cast<unsigned short>(1U << i));
+}
+
+TEST(LlvmLibcStdcBitceilUsTest, OneMoreThanPowsTwo) {
+  for (unsigned i = 1U; i != USHRT_WIDTH - 1; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_ceil_us((1U << i) + 1),
+              static_cast<unsigned short>(1U << (i + 1)));
+}