Using embedded file. Create file in your project testingFile.xml. In properties set type as embedded resource file. How is your file called? http://blog.cpodesign.com/blog/how-is-my-file-called-in-resource/

GetAllResourceFiles

var thisExe = System.Reflection.Assembly.GetExecutingAssembly();
string[] resources = thisExe.GetManifestResourceNames();
string list = "";

// Build the string of resources.
foreach (string resource in resources)
Console.WriteLine(resource);

TestMapperTests.cs

class TestMapperTests
    {
        const string EmbeddedFile = "ProjectNameNamespace.testingFile.xml";

       
        [Test]
        public void LoadKmlData_ShouldImportThreeRecordsFromFile()
        {
            // Act
             var mapper = new TestMapper();
             var resourceStream = Assembly.GetExecutingAssembly().GetManifestResourceStream(EmbeddedFile);
             var items = mapper.ParseReaderToDocument(resourceStream);
             
             // Assert
            Assert.AreEqual(3, items.Count);
        }
    }