public void LoadThemeFilesTest() { ILocation loc = null; var fileLoaderMock = new Mock <IFileLoader>(); fileLoaderMock.Setup(m => m.LoadFolder(It.IsAny <ILocation>(), It.IsAny <string[]>())) .Returns((ILocation l, string[] f) => { loc = l; return(AsyncEnumerable.Empty <IFile>()); }); var libLoader = new FolderLibraryLoader(Location.FromPath("D:\\lib"), fileLoaderMock.Object); libLoader.LoadThemeFiles("A", null); Assert.AreEqual("D:\\lib\\_themes\\A", loc.ToPath()); }