const files = {}
const watchers = {}

module.exports = {
  writeFileSync (file, data) {
    files[file] = data
    if (watchers[file]) {
      watchers[file]('change', file)
    }
  },
  watch (filename, listener) {
    watchers[filename] = listener
  },
  readFile (filename, encoding, callback) {
    callback(null, files[filename])
  }
}

@@ -191,20 +191,16 @@
 ch (file
-name
 , listen
@@ -222,20 +222,16 @@
 ers%5Bfile
-name
 %5D = list
@@ -254,60 +254,32 @@
 File
+Sync
  (file
-name, encoding, callback) %7B%0A    callback(null,
+) %7B%0A    return
  fil
@@ -289,14 +289,9 @@
 file
-name%5D)
+%5D
 %0A  %7D

Refactor fs mock