Add integration tests for ForceDriver persistence

- Created ForceDriverTests.cs with two integration tests
- Tests verify ForceDriver persists across Init/Shutdown cycles
- Tests verify scenarios use ForceDriver when calling Application.Init()
- Both tests pass successfully

Co-authored-by: tig <[email protected]>

Tests/IntegrationTests/UICatalog/ForceDriverTests.cs

@@ -0,0 +1,134 @@
+using UICatalog;
+using Xunit.Abstractions;
+
+namespace IntegrationTests.UICatalog;
+
+/// <summary>
+///     Integration tests for ForceDriver persistence when opening scenarios in UICatalog.
+/// </summary>
+public class ForceDriverTests
+{
+    private readonly ITestOutputHelper _output;
+
+    public ForceDriverTests (ITestOutputHelper output)
+    {
+        _output = output;
+    }
+
+    /// <summary>
+    ///     Tests that ForceDriver persists when opening a scenario after Init/Shutdown cycles.
+    ///     This verifies the fix for issue #4391.
+    /// </summary>
+    [Fact]
+    public void ForceDriver_Persists_Across_Init_Shutdown_Cycles ()
+    {
+        // Arrange
+        const string expectedDriver = "fake";
+        
+        ConfigurationManager.Disable (true);
+        Application.ResetState (true);
+
+        // Set ForceDriver in RuntimeConfig (simulating what UICatalog does with --driver option)
+        ConfigurationManager.RuntimeConfig = $$"""
+            {
+                "Application.ForceDriver": "{{expectedDriver}}"
+            }
+            """;
+
+        // Enable ConfigurationManager with all locations (as UICatalog does)
+        ConfigurationManager.Enable (ConfigLocations.All);
+
+        var firstDriverName = string.Empty;
+        var secondDriverName = string.Empty;
+
+        try
+        {
+            // Act - Cycle 1: Init and check driver
+            _output.WriteLine ("Cycle 1: First Init");
+            Application.Init ();
+            firstDriverName = Application.Driver?.GetName () ?? string.Empty;
+            _output.WriteLine ($"Cycle 1 driver: {firstDriverName}");
+            Application.Shutdown ();
+
+            // Act - Cycle 2: Reload RuntimeConfig and Init again (simulating scenario opening)
+            _output.WriteLine ("Cycle 2: Reload RuntimeConfig and Init again");
+            
+            // This simulates what the fix does before each scenario
+            ConfigurationManager.Load (ConfigLocations.Runtime);
+            ConfigurationManager.Apply ();
+
+            // Scenario calls Application.Init() without parameters
+            Application.Init ();
+            secondDriverName = Application.Driver?.GetName () ?? string.Empty;
+            _output.WriteLine ($"Cycle 2 driver: {secondDriverName}");
+            Application.Shutdown ();
+
+            // Assert
+            Assert.Equal (expectedDriver, firstDriverName);
+            Assert.Equal (expectedDriver, secondDriverName);
+            _output.WriteLine ($"SUCCESS: Driver '{expectedDriver}' persisted across Init/Shutdown cycles");
+        }
+        finally
+        {
+            ConfigurationManager.Disable (true);
+            Application.ResetState (true);
+        }
+    }
+
+    /// <summary>
+    ///     Tests that ForceDriver is used when a scenario calls Application.Init() without parameters.
+    ///     This simulates the actual UICatalog scenario execution flow.
+    /// </summary>
+    [Fact]
+    public void ForceDriver_Used_By_Scenario_Init ()
+    {
+        // Arrange
+        const string expectedDriver = "fake";
+        Scenario? scenario = null;
+
+        ConfigurationManager.Disable (true);
+        Application.ResetState (true);
+
+        // Set ForceDriver in RuntimeConfig
+        ConfigurationManager.RuntimeConfig = $$"""
+            {
+                "Application.ForceDriver": "{{expectedDriver}}"
+            }
+            """;
+
+        // Enable ConfigurationManager
+        ConfigurationManager.Enable (ConfigLocations.All);
+
+        try
+        {
+            // Get the first available scenario
+            var scenarios = Scenario.GetScenarios ();
+            Assert.NotEmpty (scenarios);
+            
+            scenario = scenarios[0];
+            var scenarioName = scenario.GetName ();
+            _output.WriteLine ($"Testing with scenario: {scenarioName}");
+
+            // Reload RuntimeConfig before scenario (as the fix does)
+            ConfigurationManager.Load (ConfigLocations.Runtime);
+            ConfigurationManager.Apply ();
+
+            // Scenario calls Application.Init() - it should use ForceDriver
+            Application.Init ();
+            var driverName = Application.Driver?.GetName () ?? string.Empty;
+            _output.WriteLine ($"Scenario driver: {driverName}");
+
+            // Assert
+            Assert.Equal (expectedDriver, driverName);
+            _output.WriteLine ($"SUCCESS: Scenario uses ForceDriver '{expectedDriver}'");
+
+            Application.Shutdown ();
+        }
+        finally
+        {
+            scenario?.Dispose ();
+            ConfigurationManager.Disable (true);
+            Application.ResetState (true);
+        }
+    }
+}