add failure test

Author: nickdesaulniers

libc/test/src/poll/poll_test.cpp

@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "hdr/limits_macros.h" // UINT_MAX
 #include "src/errno/libc_errno.h"
 #include "src/poll/poll.h"
 #include "test/UnitTest/Test.h"
@@ -16,3 +17,9 @@ TEST(LlvmLibcPollTest, SmokeTest) {
   ASSERT_ERRNO_SUCCESS();
   ASSERT_EQ(0, ret);
 }
+TEST(LlvmLibcPollTest, SmokeFailureTest) {
+  LIBC_NAMESPACE::libc_errno = 0;
+  int ret = LIBC_NAMESPACE::poll(nullptr, UINT_MAX, 0);
+  ASSERT_ERRNO_EQ(EINVAL);
+  ASSERT_EQ(-1, ret);
+}