Add tests for existing command line parsing

ILSpy.Tests/CommandLineArgumentsTests.cs

@@ -0,0 +1,48 @@
+using FluentAssertions;
+
+using NUnit.Framework;
+
+namespace ICSharpCode.ILSpy.Tests
+{
+	[TestFixture]
+	public class CommandLineArgumentsTests
+	{
+		[Test]
+		public void VerifyEmptyArgumentsArray()
+		{
+			var cmdLineArgs = new CommandLineArguments(new string[] { });
+
+			cmdLineArgs.AssembliesToLoad.Should().BeEmpty();
+			cmdLineArgs.SingleInstance.Should().BeNull();
+			cmdLineArgs.NavigateTo.Should().BeNull();
+			cmdLineArgs.Search.Should().BeNull();
+			cmdLineArgs.Language.Should().BeNull();
+			cmdLineArgs.NoActivate.Should().BeFalse();
+			cmdLineArgs.ConfigFile.Should().BeNull();
+		}
+
+		[Test]
+		public void VerifySeparateOption()
+		{
+			var cmdLineArgs = new CommandLineArguments(new string[] { "/separate" });
+			cmdLineArgs.SingleInstance.Should().BeFalse();
+		}
+
+		[Test]
+		public void VerifySingleInstanceOption()
+		{
+			var cmdLineArgs = new CommandLineArguments(new string[] { "/singleInstance" });
+			cmdLineArgs.SingleInstance.Should().BeTrue();
+		}
+
+		[Test]
+		public void VerifySeparateSingleInstanceOptionOrdering()
+		{
+			var cmdLineArgsCase1 = new CommandLineArguments(new string[] { "/singleInstance", "/separate" });
+			cmdLineArgsCase1.SingleInstance.Should().BeFalse();
+
+			var cmdLineArgsCase2 = new CommandLineArguments(new string[] { "/separate", "/singleInstance" });
+			cmdLineArgsCase2.SingleInstance.Should().BeTrue();
+		}
+	}
+}

ILSpy.Tests/ILSpy.Tests.csproj

@@ -39,6 +39,7 @@
     <Compile Include="Analyzers\MethodUsesAnalyzerTests.cs" />
     <Compile Include="Analyzers\TestCases\MainAssembly.cs" />
     <Compile Include="Analyzers\TypeUsedByAnalyzerTests.cs" />
+    <Compile Include="CommandLineArgumentsTests.cs" />
   </ItemGroup>
 
   <ItemGroup>