Using a filename as a function input

Mistake

Testing this function would require a unique file for every use case.

func countEmptyLinesInFile(filename string) (int, error) {
  file, err := os.Open(filename)
  if err != nil {
    return 0, err
  }
  // Handle file closure
  scanner := bufio.NewScanner(file)
  for scanner.Scan() {
  // ...
  }
}

Fix

Extract the file i/o from the function logic.

func countEmptyLines(reader io.Reader) (int, error) {
  scanner := bufio.NewScanner(reader)
  for scanner.Scan() {
  // ...
  }
}

References