diff -r bf817b825ed2 -r e081643aae2a tests/test_hash_key.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test_hash_key.cpp	Tue Feb 07 21:55:37 2023 +0100
@@ -0,0 +1,87 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "cx/hash_key.h"
+
+#include <gtest/gtest.h>
+
+TEST(cx_hash_key, functions) {
+    auto str = "my key";
+    auto len = strlen(str);
+
+    auto str_key = cx_hash_key_str(str);
+    auto bytes_key = cx_hash_key_bytes(
+            reinterpret_cast<unsigned char const *>(str), len);
+    auto obj_key = cx_hash_key(
+            reinterpret_cast<void const *>(str), len);
+
+    EXPECT_EQ(str_key.hash, bytes_key.hash);
+    EXPECT_EQ(obj_key.hash, bytes_key.hash);
+    EXPECT_EQ(str_key.len, len);
+    EXPECT_EQ(bytes_key.len, len);
+    EXPECT_EQ(bytes_key.len, len);
+    EXPECT_EQ(str_key.data.cstr, str);
+    EXPECT_EQ(bytes_key.data.cbytes, reinterpret_cast<unsigned char const *>(str));
+    EXPECT_EQ(bytes_key.data.cobj, reinterpret_cast<void const *>(str));
+}
+
+TEST(cx_hash_key, empty_string) {
+    auto str = "";
+
+    auto str_key = cx_hash_key_str(str);
+    auto bytes_key = cx_hash_key_bytes(
+            reinterpret_cast<unsigned char const *>(str), 0);
+    auto obj_key = cx_hash_key(
+            reinterpret_cast<void const *>(str), 0);
+
+    EXPECT_EQ(bytes_key.hash, 4152238450u);
+    EXPECT_EQ(str_key.hash, 4152238450u);
+    EXPECT_EQ(obj_key.hash, 4152238450u);
+    EXPECT_EQ(str_key.len, 0);
+    EXPECT_EQ(bytes_key.len, 0);
+    EXPECT_EQ(bytes_key.len, 0);
+    EXPECT_EQ(str_key.data.cstr, str);
+    EXPECT_EQ(bytes_key.data.cbytes, reinterpret_cast<unsigned char const *>(str));
+    EXPECT_EQ(bytes_key.data.cobj, reinterpret_cast<void const *>(str));
+}
+
+TEST(cx_hash_key, null_ptr) {
+    auto str_key = cx_hash_key_str(nullptr);
+    auto bytes_key = cx_hash_key_bytes(nullptr, 0);
+    auto obj_key = cx_hash_key(nullptr, 0);
+
+    EXPECT_EQ(bytes_key.hash, 1574210520u);
+    EXPECT_EQ(str_key.hash, 1574210520u);
+    EXPECT_EQ(obj_key.hash, 1574210520u);
+    EXPECT_EQ(str_key.len, 0);
+    EXPECT_EQ(bytes_key.len, 0);
+    EXPECT_EQ(bytes_key.len, 0);
+    EXPECT_EQ(str_key.data.cstr, nullptr);
+    EXPECT_EQ(bytes_key.data.cbytes, nullptr);
+    EXPECT_EQ(bytes_key.data.cobj, nullptr);
+}