Printing JUnit test results in file by changing and using the 'out' static variable of 'System' class

Question

I'm building a framework for comparing files (in my own way) using JUnit. All test cases have been packaged in a JAR which is ran independently using a .bat file I wrote. I needed to output the test results in a file instead of the console.

I was just using normal System.out.println() in the TestRunner class and also in the various test case classes for printing the output on the console.

I found a solution that I could use in the project (Method number 3 of this article). I redirected the output stream to my output file. Following is the relevant code from the TestRunner class:

public class TestRunner {
 public static void main(String[] args) {
 System.out.println("Testing Started...");
 // Save the System.out instance
 PrintStream oldPrintStream = System.out;
 FileOutputStream outFile = null;
 try {
 outFile = new FileOutputStream("result.txt");
 PrintStream newPrintStream = new PrintStream(outFile);
 System.setOut(newPrintStream);
 Result result = JUnitCore.runClasses(TestSuite.class);
 // Print the results in desired format
 } catch (FileNotFoundException ex) {
 Logger.getLogger(TestRunner.class.getName()).log(Level.SEVERE, null, ex);
 } finally {
 // Reset the old System.out instance
 System.setOut(oldPrintStream); 
 System.out.println("Testing Completed! Check output folder for result.");
 try {
 outFile.close();
 } catch (IOException ex) {
 Logger.getLogger(TestRunner.class.getName()).log(Level.SEVERE, null, ex);
 }
 }
 }
}

The code is working fine but is it the correct way to do this?

• h.j.k.: Couldn't you pipe the results in your *.bat script to the desired results file?
• Bilesh Ganguly: @h.j.k. Yes, but the generated result is going to be used further. So, this isn't the end.

Answer 1

Looks good enough, but there's some improvements in the io API you're not using. Consider:

try (OutputStream outFile = Files.newOutputStream(Paths.get("result.txt"), 
 StandardOpenOption.WRITE, StandardOpenOption.CREATE);
 PrintStream newSysOut = new PrintStream(outFile)) {
 System.setOut(newSysOut);
 Result result = JUnitCore.runClasses(TestSuite.class);
 printResults(result);
} catch (IOException ex) {
 // your code here
} finally {
 System.setOut(oldPrintStream);
}

This should give you more fine-grained Exceptions when your operations fail (not that I'm using it here).
Also you don't need to close the Resources you use yourself, because of the try-with-resources-block.

Small additional note: Your comments are extraneous for this example. I'd suggest removing them.