diff --git a/src/test/c/StringUtilTests.cpp b/src/test/c/StringUtilTests.cpp
new file mode 100644
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+++ b/src/test/c/StringUtilTests.cpp
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+// Copyright (c) 2019, offa
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// Redistributions of source code must retain the above copyright notice, this
+// list of conditions and the following disclaimer.
+//
+// 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 "seasocks/StringUtil.h"
+#include <catch2/catch.hpp>
+
+using namespace seasocks;
+
+TEST_CASE("case insensitive string comparison", "[ToStringTests]") {
+    CHECK(caseInsensitiveSame("abc def 123", "abc def 123") == true);
+    CHECK(caseInsensitiveSame("abc def 123", "abc ghi 123") == false);
+    CHECK(caseInsensitiveSame("abc", "aBc") == true);
+    CHECK(caseInsensitiveSame("", "") == true);
+    CHECK(caseInsensitiveSame("123", "123") == true);
+    CHECK(caseInsensitiveSame(" ", " ") == true);
+}
+
+TEST_CASE("replace replaces match if found", "[ToStringTests]") {
+    std::string str = "x-?-z";
+    replace(str, "-?-", "y");
+    CHECK(str == "xyz");
+}
+
+TEST_CASE("replace replaces all matches", "[ToStringTests]") {
+    std::string str = "1xx2 xx34xxxx";
+    replace(str, "xx", "---");
+    CHECK(str == "1---2 ---34------");
+}
+
+TEST_CASE("replace does nothing if no match", "[ToStringTests]") {
+    std::string str = "no match in here";
+    replace(str, "xx", "no!");
+    CHECK(str == "no match in here");
+}
+
+TEST_CASE("replace is safe to empty strings", "[ToStringTests]") {
+    std::string empty{};
+    replace(empty, "a", "b");
+    CHECK(empty == "");
+
+    std::string str = "input text";
+    replace(str, "", "aaa");
+    CHECK(str == "input text");
+
+    replace(str, " text", "");
+    CHECK(str == "input");
+}
+
+TEST_CASE("split splits input if delimiter found", "[ToStringTests]") {
+    using Catch::Matchers::Equals;
+
+    const auto result = split("123-456-789-0", '-');
+    CHECK_THAT(result, Equals<std::string>({"123", "456", "789", "0"}));
+}
+
+TEST_CASE("split returns input if delimiter not found", "[ToStringTests]") {
+    using Catch::Matchers::Equals;
+
+    const auto result = split("1-2 3-4", 'x');
+    CHECK_THAT(result, Equals<std::string>({"1-2 3-4"}));
+}
+
+TEST_CASE("split is safe to empty strings", "[ToStringTests]") {
+    using Catch::Matchers::Equals;
+
+    const auto result = split("", '-');
+    CHECK_THAT(result, Equals<std::string>({}));
+}
+
+TEST_CASE("split returns empty strings if input is delimiter", "[ToStringTests]") {
+    using Catch::Matchers::Equals;
+
+    const auto result = split("-", '-');
+    CHECK_THAT(result, Equals<std::string>({"", ""}));
+}
+
+TEST_CASE("trim whitespace removes whitespace on both ends", "[ToStringTests]") {
+    const auto result = trimWhitespace(" abc def   ");
+    CHECK(result == "abc def");
+}
+
+TEST_CASE("trim whitespace removes whitespace escape sequences", "[ToStringTests]") {
+    const auto result = trimWhitespace("\t xyz\n");
+    CHECK(result == "xyz");
+}
+
+TEST_CASE("trim whitespace is safe to empty string", "[ToStringTests]") {
+    const auto result = trimWhitespace("");
+    CHECK(result == "");
+}
+
+TEST_CASE("trim whitespace returns empty string if only whitespace", "[ToStringTests]") {
+    const auto result = trimWhitespace(" \n \t   ");
+    CHECK(result == "");
+}