fileTreeStub :: IO (Forest DirectoryTreeElement)
fileTreeStub = return [
    Node (DirectoryTreeElement "a" "/xxx/a" True) [
        Node (DirectoryTreeElement "b" "/xxx/a/b" False) []],
    Node (DirectoryTreeElement "a.b" "/xxx/a.b" False) [],
    Node (DirectoryTreeElement "c" "/xxx/c" False) [],
    Node (DirectoryTreeElement "-" "/xxx/cannotRead" False) []]
fileTreeStub :: IO (Forest DirectoryTreeElement)
fileTreeStub = return [
    Node (DirectoryTreeElement "a" "/xxx/a" True) [
        Node (DirectoryTreeElement "b" "/xxx/a/b" False) []],
    Node (DirectoryTreeElement "a.b" "/xxx/a.b" False) [],
    Node (DirectoryTreeElement "c" "/xxx/c" False) [],
    Node (DirectoryTreeElement "-" "/xxx/cannotRead" False) []]
fileTreeStub = return [
    Node (DirectoryTreeElement "a" "/xxx/a" True) [
        Node (DirectoryTreeElement "b" "/xxx/a/b" False) []],
    Node (DirectoryTreeElement "a.b" "/xxx/a.b" False) [],
    Node (DirectoryTreeElement "c" "/xxx/c" False) [],
    Node (DirectoryTreeElement "-" "/xxx/cannotRead" False) []]