diff --git a/test/libc/mem/putenv_test.c b/test/libc/mem/putenv_test.c
new file mode 100644
index 000000000..d3253ed3e
--- /dev/null
+++ b/test/libc/mem/putenv_test.c
@@ -0,0 +1,33 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Gavin Arthur Hayes                                            │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/mem/mem.h"
+#include "libc/runtime/runtime.h"
+#include "libc/testlib/testlib.h"
+
+TEST(putenv, test) {
+  EXPECT_EQ(0, clearenv());
+  EXPECT_EQ(0, putenv("hi=there"));
+  EXPECT_STREQ("there", getenv("hi"));
+  EXPECT_EQ(0, clearenv());
+  EXPECT_EQ(0, putenv("hi=theretwo"));
+  EXPECT_STREQ("theretwo", getenv("hi"));
+  EXPECT_EQ(0, clearenv());
+  EXPECT_EQ(0, setenv("hi", "therethree", 0));
+  EXPECT_STREQ("therethree", getenv("hi"));
+}