java - Testing main method by junit

I wrote a class which takes input from console and arguments in main method. The main method calls different methods for different console inputs and it calls different function for different arguments. So i want to test this main method with Junit by mimicking these inputs from a file. how can i do it? Is there any special provision in junit to test the main method of the class?

Answer

To provide the input from a file, make a FileInputStream and set that as the System.in stream. You'll probably want to set the original back after the main method has finished to make sure anything using it later still works (other tests, JUnit itself...)

Here's an example:

@Test
public void testMain() throws IOException {
    System.out.println("main");
    String[] args = null;
    final InputStream original = System.in;
    final FileInputStream fips = new FileInputStream(new File("[path_to_file]"));
    System.setIn(fips);
    Main.main(args);
    System.setIn(original);

}

In your actual code you'll want to handle any IOExceptions and use something better than a full path to the file (get it via the classloader), but this gives you the general idea.