1 files changed, 48 insertions, 0 deletions
diff --git a/libc/test/src/strings/strncasecmp_test.cpp b/libc/test/src/strings/strncasecmp_test.cpp
new file mode 100644
index 000000000000..870574ed9507
--- /dev/null
+++ b/libc/test/src/strings/strncasecmp_test.cpp
@@ -0,0 +1,48 @@
+//===-- Unittests for strncasecmp -----------------------------------------===//
+//
+// 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/strings/strncasecmp.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStrNCaseCmpTest,
+     EmptyStringsShouldReturnZeroWithSufficientLength) {
+  const char *s1 = "";
+  const char *s2 = "";
+  int result = LIBC_NAMESPACE::strncasecmp(s1, s2, 1);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::strncasecmp(s2, s1, 1);
+  ASSERT_EQ(result, 0);
+}
+
+TEST(LlvmLibcStrNCaseCmpTest,
+     EmptyStringShouldNotEqualNonEmptyStringWithSufficientLength) {
+  const char *empty = "";
+  const char *s2 = "abc";
+  int result = LIBC_NAMESPACE::strncasecmp(empty, s2, 3);
+  // This should be '\0' - 'a' = -97
+  ASSERT_LT(result, 0);
+
+  // Similar case if empty string is second argument.
+  const char *s3 = "123";
+  result = LIBC_NAMESPACE::strncasecmp(s3, empty, 3);
+  // This should be '1' - '\0' = 49
+  ASSERT_GT(result, 0);
+}
+
+TEST(LlvmLibcStrNCaseCmpTest, Case) {
+  const char *s1 = "aB";
+  const char *s2 = "ab";
+  int result = LIBC_NAMESPACE::strncasecmp(s1, s2, 2);
+  ASSERT_EQ(result, 0);
+
+  // Verify operands reversed.
+  result = LIBC_NAMESPACE::strncasecmp(s2, s1, 2);
+  ASSERT_EQ(result, 0);
+}