feat(test): Adding tests to ensure that the test mode values are not changed

sdk/digitaltwins/Azure.DigitalTwins.Core/tests/EnsureCorrectTestMode.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.IO;
+using System.Reflection;
+using Azure.Core.TestFramework;
+using FluentAssertions;
+using Microsoft.Extensions.Configuration;
+using NUnit.Framework;
+
+namespace Azure.DigitalTwins.Core.Tests
+{
+    [Category("Unit")]
+    [Parallelizable(ParallelScope.All)]
+    public class EnsureCorrectTestMode
+    {
+        [Test]
+        // The PR tests use the value in the common.config.json to determine the mode to run the tests.
+        // This test ensures that the value in common.config.json is not changed.
+        public void CommonConfig_SetTo_PlaybackMode()
+        {
+            // arrange
+            string codeBase = Assembly.GetExecutingAssembly().CodeBase;
+            var uri = new UriBuilder(codeBase);
+            string path = Uri.UnescapeDataString(uri.Path);
+            string workingDirectory = Path.GetDirectoryName(path);
+            string testSettingsCommonPath = Path.Combine(
+                workingDirectory,
+                "config",
+                "common.config.json");
+
+            var testsSettingsConfigBuilder = new ConfigurationBuilder();
+            testsSettingsConfigBuilder.AddJsonFile(testSettingsCommonPath);
+
+            IConfiguration config = testsSettingsConfigBuilder.Build();
+
+            // act
+            var testSettings = config.Get<TestSettings>();
+
+            // assert
+            testSettings.TestMode.Should().Be(RecordedTestMode.Playback, "The PR pipeline should always run the e2e tests in the playback mode so the value of TestMode should not be changed in the common.config.json file.");
+        }
+    }
+}