Moved analyzer tests to its own project

Also moves tests to `./test` which makes it possible
for all test projects to share the same .editorconfig
files and similar.

test/Spectre.Console.Tests/Unit/Cli/Annotations/CommandArgumentAttributeTests.cs

@@ -0,0 +1,64 @@
+using Shouldly;
+using Spectre.Console.Cli;
+using Xunit;
+
+namespace Spectre.Console.Tests.Unit.Cli.Annotations
+{
+    public sealed partial class CommandArgumentAttributeTests
+    {
+        [Fact]
+        public void Should_Not_Contain_Options()
+        {
+            // Given, When
+            var result = Record.Exception(() => new CommandArgumentAttribute(0, "--foo <BAR>"));
+
+            // Then
+            result.ShouldNotBe(null);
+            result.ShouldBeOfType<CommandTemplateException>().And(exception =>
+                exception.Message.ShouldBe("Arguments can not contain options."));
+        }
+
+        [Theory]
+        [InlineData("<FOO> <BAR>")]
+        [InlineData("[FOO] [BAR]")]
+        [InlineData("[FOO] <BAR>")]
+        [InlineData("<FOO> [BAR]")]
+        public void Should_Not_Contain_Multiple_Value_Names(string template)
+        {
+            // Given, When
+            var result = Record.Exception(() => new CommandArgumentAttribute(0, template));
+
+            // Then
+            result.ShouldNotBe(null);
+            result.ShouldBeOfType<CommandTemplateException>().And(exception =>
+                exception.Message.ShouldBe("Multiple values are not supported."));
+        }
+
+        [Theory]
+        [InlineData("<>")]
+        [InlineData("[]")]
+        public void Should_Not_Contain_Empty_Value_Name(string template)
+        {
+            // Given, When
+            var result = Record.Exception(() => new CommandArgumentAttribute(0, template));
+
+            // Then
+            result.ShouldNotBe(null);
+            result.ShouldBeOfType<CommandTemplateException>().And(exception =>
+                exception.Message.ShouldBe("Values without name are not allowed."));
+        }
+
+        [Theory]
+        [InlineData("<FOO>", true)]
+        [InlineData("[FOO]", false)]
+        public void Should_Parse_Valid_Options(string template, bool required)
+        {
+            // Given, When
+            var result = new CommandArgumentAttribute(0, template);
+
+            // Then
+            result.ValueName.ShouldBe("FOO");
+            result.IsRequired.ShouldBe(required);
+        }
+    }
+}