Add XUnit test for HandleDoubleAndSingleQuote in CompletionHelpers class (PowerShell#25181)

Author: ArmaanMcleod

test/xUnit/csharp/test_CompletionHelpers.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Management.Automation;
+using Xunit;
+
+namespace PSTests.Parallel
+{
+    public class CompletionHelpersTests
+    {
+        [Theory]
+        [InlineData("", "", "")]
+        [InlineData("\"", "", "\"")]
+        [InlineData("'", "", "'")]
+        [InlineData("\"word\"", "word", "\"")]
+        [InlineData("'word'", "word", "'")]
+        [InlineData("\"word", "word", "\"")]
+        [InlineData("'word", "word", "'")]
+        [InlineData("word\"", "word\"", "")]
+        [InlineData("word'", "word'", "")]
+        [InlineData("\"word's\"", "word's", "\"")]
+        [InlineData("'word\"", "'word\"", "")]
+        [InlineData("\"word'", "\"word'", "")]
+        [InlineData("'word\"s'", "word\"s", "'")]
+        public void TestHandleDoubleAndSingleQuote(string wordToComplete, string expectedWordToComplete, string expectedQuote)
+        {
+            string quote = CompletionHelpers.HandleDoubleAndSingleQuote(ref wordToComplete);
+            Assert.Equal(expectedQuote, quote);
+            Assert.Equal(expectedWordToComplete, wordToComplete);
+        }
+    }
+}