diff --git a/libc/test/src/stdbit/stdc_has_single_bit_ul_test.cpp b/libc/test/src/stdbit/stdc_has_single_bit_ul_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_has_single_bit_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_has_single_bit_ul.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcCountOnesUlTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_has_single_bit_ul(0U), false);
+}
+
+TEST(LlvmLibcStdcCountOnesUlTest, OneHot) {
+  for (unsigned i = 0U; i != ULONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_has_single_bit_ul(1UL << i), true);
+}
diff --git a/libc/test/src/stdbit/stdc_has_single_bit_ull_test.cpp b/libc/test/src/stdbit/stdc_has_single_bit_ull_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_has_single_bit_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_has_single_bit_ull.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcCountOnesUllTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_has_single_bit_ull(0U), false);
+}
+
+TEST(LlvmLibcStdcCountOnesUllTest, OneHot) {
+  for (unsigned i = 0U; i != ULLONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_has_single_bit_ull(1ULL << i), true);
+}
diff --git a/libc/test/src/stdbit/stdc_has_single_bit_us_test.cpp b/libc/test/src/stdbit/stdc_has_single_bit_us_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_has_single_bit_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_has_single_bit_us.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcCountOnesUsTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_has_single_bit_us(0U), false);
+}
+
+TEST(LlvmLibcStdcCountOnesUsTest, OneHot) {
+  for (unsigned i = 0U; i != USHRT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_has_single_bit_us(1U << i), true);
+}