diff --git a/test/UnitTests/Microsoft.Testing.Platform.UnitTests/CommandLine/ResponseFileHelperTests.cs b/test/UnitTests/Microsoft.Testing.Platform.UnitTests/CommandLine/ResponseFileHelperTests.cs
new file mode 100644
index 0000000000..a4bd24cdc0
--- /dev/null
+++ b/test/UnitTests/Microsoft.Testing.Platform.UnitTests/CommandLine/ResponseFileHelperTests.cs
@@ -0,0 +1,158 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.Testing.Platform.UnitTests;
+
+[TestClass]
+public sealed class ResponseFileHelperTests
+{
+    [TestMethod]
+    public void SplitCommandLine_EmptyString_ReturnsEmpty()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine(string.Empty)];
+
+        Assert.IsEmpty(result);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_WhitespaceOnly_ReturnsEmpty()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("   \t  ")];
+
+        Assert.IsEmpty(result);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_NullInput_ThrowsNullReferenceException()
+        => Assert.Throws<NullReferenceException>(() => ResponseFileHelper.SplitCommandLine(null!).ToArray());
+
+    [TestMethod]
+    public void SplitCommandLine_SingleToken_ReturnsSingleElement()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("hello")];
+
+        Assert.HasCount(1, result);
+        Assert.AreEqual("hello", result[0]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_MultipleTokens_ReturnsAllElements()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("one two three")];
+
+        Assert.HasCount(3, result);
+        Assert.AreEqual("one", result[0]);
+        Assert.AreEqual("two", result[1]);
+        Assert.AreEqual("three", result[2]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_LeadingAndTrailingWhitespace_IsIgnored()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("  hello world  ")];
+
+        Assert.HasCount(2, result);
+        Assert.AreEqual("hello", result[0]);
+        Assert.AreEqual("world", result[1]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_MultipleSpacesBetweenTokens_TokensSplitCorrectly()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("a   b")];
+
+        Assert.HasCount(2, result);
+        Assert.AreEqual("a", result[0]);
+        Assert.AreEqual("b", result[1]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_QuotedStringWithSpace_ReturnsSingleToken()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("\"hello world\"")];
+
+        Assert.HasCount(1, result);
+        Assert.AreEqual("hello world", result[0]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_QuotedAndUnquotedTokens_SplitsCorrectly()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("--opt \"some value\" other")];
+
+        Assert.HasCount(3, result);
+        Assert.AreEqual("--opt", result[0]);
+        Assert.AreEqual("some value", result[1]);
+        Assert.AreEqual("other", result[2]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_MultipleQuotedTokens_EachUnquotedSeparately()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("\"foo bar\" \"baz qux\"")];
+
+        Assert.HasCount(2, result);
+        Assert.AreEqual("foo bar", result[0]);
+        Assert.AreEqual("baz qux", result[1]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_OptionWithArgument_ReturnsSeparateTokens()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("--filter TestClass1")];
+
+        Assert.HasCount(2, result);
+        Assert.AreEqual("--filter", result[0]);
+        Assert.AreEqual("TestClass1", result[1]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_DashPrefixedOptions_PreserveDashes()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("--timeout 30 -v")];
+
+        Assert.HasCount(3, result);
+        Assert.AreEqual("--timeout", result[0]);
+        Assert.AreEqual("30", result[1]);
+        Assert.AreEqual("-v", result[2]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_QuotedStringContainingMultipleSpaces_PreservesInternalSpaces()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("\"a  b  c\"")];
+
+        Assert.HasCount(1, result);
+        Assert.AreEqual("a  b  c", result[0]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_UnclosedQuote_ReturnsEmpty()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("\"hello world")];
+
+        Assert.IsEmpty(result);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_TabSeparatedTokens_SplitsOnTab()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("one\ttwo")];
+
+        Assert.HasCount(2, result);
+        Assert.AreEqual("one", result[0]);
+        Assert.AreEqual("two", result[1]);
+    }
+
+    [TestMethod]
+    public void SplitCommandLine_RealWorldResponseFileLine_ParsesCorrectly()
+    {
+        string[] result = [.. ResponseFileHelper.SplitCommandLine("--filter \"FullyQualifiedName~MyNamespace.MyClass\" --timeout 60")];
+
+        Assert.HasCount(4, result);
+        Assert.AreEqual("--filter", result[0]);
+        Assert.AreEqual("FullyQualifiedName~MyNamespace.MyClass", result[1]);
+        Assert.AreEqual("--timeout", result[2]);
+        Assert.AreEqual("60", result[3]);
+    }
+}