Improved exports for testing

Author: jlongster

src/fs-externs.js

@@ -5,8 +5,10 @@
 Module.FS = class {
   constructor() {
     this.ErrnoError = class {};
+    this.filesystems = {}
   }
   mount() {}
+  unmount() {}
   isRoot() {}
   isFile() {}
   isDir() {}