JUnit asserting two Strings whether they're equal or not

Question

So I looked up this question and tried it, but with no success.

My code should be testing if the method is correctly outputing the text onto the console by reading it back in using Streams.

    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    PrintStream myStream = new PrintStream(outStream);
    System.setOut(myStream);
    o.doSomething(); //printing out Hi
    System.out.flush();
    System.setOut(savedOldStream);//setting it back to System.out
    assertEquals(outStream.toString(),"Hi");

but everytime I run JUnit it fails. I also tried: assertTrue(outStream.toString().equals("Hi")); but this didn't work either.

This is the doSomething() method:

public void doSomething () {
    System.out.println("Hi");
}

What do you mean by "*didn't work*"? What actually happens? Are you getting any errors or just a failed assertion? — PM 77-1, Jun 01 '15 at 17:48
There is no need to re-assign the `System.out` to test this. You can pass the `ByteArrayOutputStream` to the `doSomething()` method. — M A, Jun 01 '15 at 18:25

score 9 · Accepted Answer · answered Jun 01 '15 at 17:50

9

PrintStream#println(String str) appends a newline at the end of the string. Therefore, your assertion should trim down the additional line:

assertEquals(outStream.toString().trim(),"Hi");

answered Jun 01 '15 at 17:50

M A

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Writing to `System.out` will not write anything in the `ByteArrayOutputStream`. – Jesper Jun 01 '15 at 17:54
Thank you very much! SO using System.out.print would also fix the problem? – NhatNienne Jun 01 '15 at 18:19
@Jesper The OP has re-assigned `System.out`. – M A Jun 01 '15 at 18:20
@NhatNienne Yes using `print` would avoid the newline. – M A Jun 01 '15 at 18:21
Agree. For this case, the OP could do as you suggested: passing the output stream as param. – M A Jun 01 '15 at 18:24

JUnit asserting two Strings whether they're equal or not

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