Create unit tests for Calculator plugin (#6356)

* Refactored logic and made it unit testable

* Changes after code review

* Added to build steps, and modified bracket to new class with unittest. Validates complexer cases now.

Co-authored-by: p-storm <paul.de.man@gmail.com>

src/modules/launcher/Plugins/Microsoft.Plugin.Calculator/BracketHelper.cs

@@ -0,0 +1,87 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.Plugin.Calculator
+{
+    public static class BracketHelper
+    {
+        public static bool IsBracketComplete(string query)
+        {
+            if (string.IsNullOrWhiteSpace(query))
+            {
+                return true;
+            }
+
+            var valueTuples = query
+                .Select(BracketTrail)
+                .Where(r => r != default);
+
+            var trailTest = new Stack<TrailType>();
+
+            foreach (var (direction, type) in valueTuples)
+            {
+                switch (direction)
+                {
+                    case TrailDirection.Open:
+                        trailTest.Push(type);
+                        break;
+                    case TrailDirection.Close:
+                        // Try to get item out of stack
+                        if (!trailTest.TryPop(out var popped))
+                        {
+                            return false;
+                        }
+
+                        if (type != popped)
+                        {
+                            return false;
+                        }
+
+                        continue;
+                    default:
+                    {
+                        throw new ArgumentOutOfRangeException(nameof(direction), direction, "Can't process value");
+                    }
+                }
+            }
+
+            return !trailTest.Any();
+        }
+
+        private static (TrailDirection direction, TrailType type) BracketTrail(char @char)
+        {
+            switch (@char)
+            {
+                case '(':
+                    return (TrailDirection.Open, TrailType.Round);
+                case ')':
+                    return (TrailDirection.Close, TrailType.Round);
+                case '[':
+                    return (TrailDirection.Open, TrailType.Bracket);
+                case ']':
+                    return (TrailDirection.Close, TrailType.Bracket);
+                default:
+                    return default;
+            }
+        }
+
+        private enum TrailDirection
+        {
+            None,
+            Open,
+            Close,
+        }
+
+        private enum TrailType
+        {
+            None,
+            Bracket,
+            Round,
+        }
+    }
+}