adding testcase for xml declaration vehicle without airdrag component

VectoCore/VectoCoreTest/VectoCoreTest.csproj

@@ -2546,6 +2546,9 @@
   <ItemGroup>
     <Content Include="TestData\XML\XMLReaderDeclaration\vecto_engine-sample.xml" />
     <Content Include="TestData\XML\XMLReaderDeclaration\vecto_gearbox-sample.xml" />
+    <Content Include="TestData\XML\XMLReaderDeclaration\vecto_vehicle-sample_noAirdrag.xml">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
     <Content Include="TestData\XML\XMLReaderDeclaration\vecto_vehicle-sample.xml">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>

VectoCore/VectoCoreTest/XML/XMLDeclarationInputTest.cs

@@ -56,11 +56,18 @@ namespace TUGraz.VectoCore.Tests.XML
 	public class XMLDeclarationInputTest
 	{
 		const string SampleVehicleDecl = "TestData/XML/XMLReaderDeclaration/vecto_vehicle-sample.xml";
+		const string SampleVehicleDeclNoAirdrag = "TestData/XML/XMLReaderDeclaration/vecto_vehicle-sample_noAirdrag.xml";
 		const string SampleVehicleFullDecl = "TestData/XML/XMLReaderDeclaration/vecto_vehicle-sample_FULL.xml";
 
 		const string SampleVehicleFullDeclCertificationOptions =
 			"TestData/XML/XMLReaderDeclaration/vecto_vehicle-sample_certificationOptions.xml";
 
+		[OneTimeSetUp]
+		public void Init()
+		{
+			Directory.SetCurrentDirectory(TestContext.CurrentContext.TestDirectory);
+		}
+
 		[TestCase]
 		public void TestXMLInputEng()
 		{
@@ -330,6 +337,16 @@ namespace TUGraz.VectoCore.Tests.XML
 			Assert.AreEqual(1.0, inputDataProvider.RetarderInputData.Ratio);
 		}
 
+		[TestCase]
+		public void TestVehicleInputNoAirdrag()
+		{
+			var reader = XmlReader.Create(SampleVehicleDeclNoAirdrag);
+
+			var inputDataProvider = new XMLDeclarationInputDataProvider(reader, true);
+
+			Assert.IsNull(inputDataProvider.AirdragInputData.AirDragArea);
+		}
+
 		[TestCase]
 		public void TestXMLPowertrainGeneration()
 		{