Adding unit tests for settings constructor

src/Spectre.Console.Tests/Unit/Cli/CommandAppTests.Constructor.cs

@@ -0,0 +1,106 @@
+using Shouldly;
+using Spectre.Console.Cli;
+using Spectre.Console.Testing;
+using Spectre.Console.Tests.Data;
+using VerifyXunit;
+using Xunit;
+
+namespace Spectre.Console.Tests.Unit.Cli
+{
+    public sealed partial class CommandAppTests
+    {
+        public class NullableSettings : CommandSettings
+        {
+            public NullableSettings(bool? detailed, string[] extra)
+            {
+                Detailed = detailed;
+                Extra = extra;
+            }
+
+            [CommandOption("-d")]
+            public bool? Detailed { get; }
+
+            [CommandArgument(0, "[extra]")]
+            public string[] Extra { get; }
+        }
+
+        public class NullableWithInitSettings : CommandSettings
+        {
+            [CommandOption("-d")]
+            public bool? Detailed { get; init; }
+
+            [CommandArgument(0, "[extra]")]
+            public string[] Extra { get; init; }
+        }
+
+        public class NullableCommand : Command<NullableSettings>
+        {
+            public override int Execute(CommandContext context, NullableSettings settings) => 0;
+        }
+
+        public class NullableWithInitCommand : Command<NullableWithInitSettings>
+        {
+            public override int Execute(CommandContext context, NullableWithInitSettings settings) => 0;
+        }
+
+        [Fact]
+        public void Nullable_objects_in_settings_are_populated_properly()
+        {
+            // Given
+            var fixture = new CommandAppFixture();
+            fixture.Configure(configurator =>
+            {
+                configurator.SetApplicationName("myapp");
+                configurator.AddCommand<NullableCommand>("null");
+            });
+
+            // When
+            var (_, _, _, settings) = fixture.Run("null");
+            var nullableSettings = (NullableSettings)settings;
+
+            // Then
+            nullableSettings.Detailed.ShouldBeNull();
+            nullableSettings.Extra.ShouldBeNull();
+        }
+
+        [Fact]
+        public void Nullable_objects_with_init_in_settings_are_populated_properly()
+        {
+            // Given
+            var fixture = new CommandAppFixture();
+            fixture.Configure(configurator =>
+            {
+                configurator.SetApplicationName("myapp");
+                configurator.AddCommand<NullableWithInitCommand>("null");
+            });
+
+            // When
+            var (_, _, _, settings) = fixture.Run("null");
+            var nullableSettings = (NullableWithInitSettings)settings;
+
+            // Then
+            nullableSettings.Detailed.ShouldBeNull();
+            nullableSettings.Extra.ShouldBeNull();
+        }
+
+        [Fact]
+        public void Regular_settings_are_populated_properly()
+        {
+            // Given
+            var fixture = new CommandAppFixture();
+            fixture.Configure(configurator =>
+            {
+                configurator.SetApplicationName("myapp");
+                configurator.AddCommand<NullableCommand>("null");
+            });
+
+            // When
+            var (_, _, _, settings) = fixture.Run("null", "-d", "true", "first-item");
+            var nullableSettings = (NullableSettings)settings;
+
+            // Then
+            nullableSettings.Detailed.ShouldBe(true);
+            nullableSettings.Extra.ShouldBe(new[] { "first-item" });
+        }
+    }
+}