how to accept input from user in Junit console

Question

I am trying to write Junit test case for the function given below:

class A{
  int i;
  void set()
  {
    Scanner in=new Scanner(System.in);
    i=in.nextInt();
  }
}

Now my problem is when i create a Junit test case for it, it does not except input from user:

 public void testSet() throws FileNotFoundException {
    System.out.println("set");
    A instance = new A();
    int i=1;
    instance.set(i);
    // TODO review the generated test code and remove the default call to fail.
    //fail("The test case is a prototype.");
}

Please suggets what should i do to accept input from user.

You don't need input from user in JUnit tests. If you need to test with some `InputStream`, attach it to your `OutputStream` and feed input programmatically. — Victor Sorokin, Nov 03 '12 at 19:19
Really, you should design your code so that any code under test doesn't need to read from `System.in`, but instead reads from a passed-in `InputStream` or the like. — Louis Wasserman, Nov 03 '12 at 19:21
i know but that's my requirement..is there no way to enter input from user ...and test the method using Junit — user1778824, Nov 03 '12 at 19:25
The purpose of using JUnit is for performing automated tests. IMO, what you are trying to achieve is against that purpose. You should be creating some test-fixtures instead. — Bhesh Gurung, Nov 03 '12 at 19:26
but i really need to test a method which takes input from user...is there no way by which i can achieve this? — user1778824, Nov 03 '12 at 19:29
While @Victor's suggestion is the best option for your need, data could be fed into testcases through the DataProviders of TestNG. And porting testcases from JUnit to TestNG requires very little effort. — Arun Manivannan, Nov 03 '12 at 19:40

score 7 · Answer 1 · answered Nov 03 '12 at 19:48

You can use System.setIn() to mock user input:

String inputData = "user input data";
System.setIn(new java.io.ByteArrayInputStream(inputData.getBytes()));

Now if you call your set() method it will read the data from your string rather than from standard input.

how to accept input from user in Junit console

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