public void TestExtensionExtraction(string fileName, string expectedExtension)
{
var environmentPathServiceMock = new Mock <IEnvironmentPathService>();
environmentPathServiceMock
.Setup(m => m.GetExtension(It.IsAny <string>()))
.Returns <string>(Path.GetExtension);
var pathService = new PathService(environmentPathServiceMock.Object);
var actualExtension = pathService.GetExtension(fileName);
Assert.Equal(expectedExtension, actualExtension);
}