how to test functions who use java io classes like LineNumberReader and FileReader

[Jigar Gosar]

I have following method in my class, I was wondering how could i write a unit test for a method that does file io, and uses java io classes such as FileReader, and LineNumberReader. I did some googling on "junit java io" "junit testing LineNumberReader" but didnot find anything useful.

Any help is appreciated.

 public void load(String file)
    {
        try
        {
            FileReader fr = new FileReader(file);
            LineNumberReader lnr = new LineNumberReader(fr);
            String line;
            for (int i = 0; i < 9; i++)
            {
                line = lnr.readLine();
                String[] arr = line.split("\\s+");
                for (int j = 0; j < 9; j++)
                {
                    grid[i][j] = Integer.parseInt(arr[j]);
                }
            }
        }
        catch (NumberFormatException e)
        {
            e.printStackTrace();
        }
        catch (FileNotFoundException e)
        {
            e.printStackTrace();  
        }
        catch (IOException e)
        {
            e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
        }
    }   

[ March 09, 2006: Message edited by: Jigar Gosar ]

[Ernest Friedman-Hill]

Break the method into two as shown, then test the non-public one using data in a StringReader:

public void load(String file) throws IOException {
    FileReader fr = new FileReader(file);
    try {
        load(fr);
    } finally {
        fr.close();
    }
}
 
void load(Reader r) throws IOException {
    try {
        LineNumberReader lnr = new LineNumberReader(r);
        // The rest of your existing method goes here
        // but don't close "r"