diff --git a/libc/test/integration/src/unistd/fork_test.cpp b/libc/test/integration/src/unistd/fork_test.cpp
@@ -8,6 +8,8 @@
 
 #include "src/signal/raise.h"
 #include "src/sys/wait/wait.h"
+#include "src/sys/wait/wait4.h"
+#include "src/sys/wait/waitpid.h"
 #include "src/unistd/fork.h"
 
 #include "utils/IntegrationTest/test.h"
@@ -17,6 +19,11 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+// The tests wait4 and waitpid are present as tests for those functions
+// really and not for the fork function. They are here along with the tests
+// for fork because it is convenient to invoke and test them after forking
+// a child.
+
 void fork_and_wait_normal_exit() {
   pid_t pid = __llvm_libc::fork();
   if (pid == 0)
@@ -29,6 +36,33 @@ void fork_and_wait_normal_exit() {
   ASSERT_TRUE(WIFEXITED(status));
 }
 
+void fork_and_wait4_normal_exit() {
+  pid_t pid = __llvm_libc::fork();
+  if (pid == 0)
+    return; // Just end without any thing special.
+  ASSERT_TRUE(pid > 0);
+  int status;
+  struct rusage usage;
+  usage.ru_utime = {0, 0};
+  usage.ru_stime = {0, 0};
+  pid_t cpid = __llvm_libc::wait4(pid, &status, 0, &usage);
+  ASSERT_TRUE(cpid > 0);
+  ASSERT_EQ(cpid, pid);
+  ASSERT_TRUE(WIFEXITED(status));
+}
+
+void fork_and_waitpid_normal_exit() {
+  pid_t pid = __llvm_libc::fork();
+  if (pid == 0)
+    return; // Just end without any thing special.
+  ASSERT_TRUE(pid > 0);
+  int status;
+  pid_t cpid = __llvm_libc::waitpid(pid, &status, 0);
+  ASSERT_TRUE(cpid > 0);
+  ASSERT_EQ(cpid, pid);
+  ASSERT_TRUE(WIFEXITED(status));
+}
+
 void fork_and_wait_signal_exit() {
   pid_t pid = __llvm_libc::fork();
   if (pid == 0)
@@ -42,8 +76,41 @@ void fork_and_wait_signal_exit() {
   ASSERT_TRUE(WTERMSIG(status) == SIGUSR1);
 }
 
+void fork_and_wait4_signal_exit() {
+  pid_t pid = __llvm_libc::fork();
+  if (pid == 0)
+    __llvm_libc::raise(SIGUSR1);
+  ASSERT_TRUE(pid > 0);
+  int status;
+  struct rusage usage;
+  usage.ru_utime = {0, 0};
+  usage.ru_stime = {0, 0};
+  pid_t cpid = __llvm_libc::wait4(pid, &status, 0, &usage);
+  ASSERT_TRUE(cpid > 0);
+  ASSERT_EQ(cpid, pid);
+  ASSERT_FALSE(WIFEXITED(status));
+  ASSERT_TRUE(WTERMSIG(status) == SIGUSR1);
+}
+
+void fork_and_waitpid_signal_exit() {
+  pid_t pid = __llvm_libc::fork();
+  if (pid == 0)
+    __llvm_libc::raise(SIGUSR1);
+  ASSERT_TRUE(pid > 0);
+  int status;
+  pid_t cpid = __llvm_libc::waitpid(pid, &status, 0);
+  ASSERT_TRUE(cpid > 0);
+  ASSERT_EQ(cpid, pid);
+  ASSERT_FALSE(WIFEXITED(status));
+  ASSERT_TRUE(WTERMSIG(status) == SIGUSR1);
+}
+
 TEST_MAIN(int argc, char **argv, char **envp) {
   fork_and_wait_normal_exit();
+  fork_and_wait4_normal_exit();
+  fork_and_waitpid_normal_exit();
   fork_and_wait_signal_exit();
+  fork_and_wait4_signal_exit();
+  fork_and_waitpid_signal_exit();
   return 0;
 }
diff --git a/libc/test/src/sys/CMakeLists.txt b/libc/test/src/sys/CMakeLists.txt
@@ -3,3 +3,4 @@ add_subdirectory(resource)
 add_subdirectory(sendfile)
 add_subdirectory(stat)
 add_subdirectory(utsname)
+add_subdirectory(wait)
diff --git a/libc/test/src/sys/wait/CMakeLists.txt b/libc/test/src/sys/wait/CMakeLists.txt
@@ -0,0 +1,25 @@
+add_libc_testsuite(libc_sys_wait_unittests)
+
+add_libc_unittest(
+  waitpid_test
+  SUITE
+    libc_sys_stat_unittests
+  SRCS
+    waitpid_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.sys_wait
+    libc.src.sys.wait.waitpid
+)
+
+add_libc_unittest(
+  wait4_test
+  SUITE
+    libc_sys_stat_unittests
+  SRCS
+    wait4_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.sys_wait
+    libc.src.sys.wait.wait4
+)
diff --git a/libc/test/src/sys/wait/wait4_test.cpp b/libc/test/src/sys/wait/wait4_test.cpp
@@ -0,0 +1,23 @@
+//===-- Unittests for wait4 -----------------------------------------------===//
+//
+// 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/sys/wait/wait4.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+#include <errno.h>
+#include <sys/wait.h>
+
+// The test here is a simpl test for WNOHANG functionality. For a more
+// involved test, look at fork_test.
+
+TEST(LlvmLibcwait4Test, NoHangTest) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  int status;
+  ASSERT_THAT(__llvm_libc::wait4(-1, &status, WNOHANG, nullptr), Fails(ECHILD));
+}
diff --git a/libc/test/src/sys/wait/waitpid_test.cpp b/libc/test/src/sys/wait/waitpid_test.cpp
@@ -0,0 +1,23 @@
+//===-- Unittests for waitpid ---------------------------------------------===//
+//
+// 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/sys/wait/waitpid.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+#include <errno.h>
+#include <sys/wait.h>
+
+// The test here is a simpl test for WNOHANG functionality. For a more
+// involved test, look at fork_test.
+
+TEST(LlvmLibcWaitPidTest, NoHangTest) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  int status;
+  ASSERT_THAT(__llvm_libc::waitpid(-1, &status, WNOHANG), Fails(ECHILD));
+}