Fix tests syntax for jest

Most tests could not run with jest because of syntax difference between
the old test runner.

src/Terminal/DirectoryHelpers.ts

@@ -35,7 +35,7 @@ export function removeTrailingSlash(s: string): string {
  * Checks whether a string is a valid filename. Only used for the filename itself,
  * not the entire filepath
  */
-function isValidFilename(filename: string): boolean {
+export function isValidFilename(filename: string): boolean {
   // Allows alphanumerics, hyphens, underscores, and percentage signs
   // Must have a file extension
   const regex = /^[.a-zA-Z0-9_-]+[.][a-zA-Z0-9]+(?:-\d+(?:\.\d*)?%-INC)?$/;
@@ -48,7 +48,7 @@ function isValidFilename(filename: string): boolean {
  * Checks whether a string is a valid directory name. Only used for the directory itself,
  * not an entire path
  */
-function isValidDirectoryName(name: string): boolean {
+ export function isValidDirectoryName(name: string): boolean {
   // Allows alphanumerics, hyphens, underscores, and percentage signs.
   // Name can begin with a single period, but otherwise cannot have any
   const regex = /^.?[a-zA-Z0-9_-]+$/;