assertEquals在两个看似相同的字符串上失败了

Question

Here is my test:

@Test
public void testAddPaperConfirm()
{
    String input = "P\n" +
                    "The Life of Geoff the Platypus";
    InputStream testInput = new ByteArrayInputStream(input.getBytes());
    System.setOut(new PrintStream(testOutput));
    System.setIn(testInput);
    testReviewSystem.main(new String[] {});
    assertEquals(testOutput.toString(), "What do you want to do?\n" +
            "O = Overview, P = Add Paper, R = Add Review, [num] = Detail of that paper, X = exit\n" +
            "What is the title of the paper?\n" +
            "[Paper added]\n"
            + "What do you want to do?\n" +
            "O = Overview, P = Add Paper, R = Add Review, [num] = Detail of that paper, X = exit\n");
}

When I look at the two strings I'm told they're identical.

Answer 1

It is failing because they are not identical.

Two strings that look identical can be diferent. There are many bytes that can't be representated and shown.

For example ascii code 0 and ascii code 1, they'd look identical but they aren't.

http://www.ascii-code.com/

Answer 2

I think that you're running your tests on windows and it outputs \\r\\n instead of \\n as line separator. You can try this by changing your assert to the following code.

assertEquals(testOutput.toString(), "What do you want to do?\r\n" +
        "O = Overview, P = Add Paper, R = Add Review, [num] = Detail of that paper, X = exit\r\n" +
        "What is the title of the paper?\r\n" +
        "[Paper added]\r\n"
        + "What do you want to do?\r\n" +
        "O = Overview, P = Add Paper, R = Add Review, [num] = Detail of that paper, X = exit\r\n")

I've written a test library named System Rules that makes testing command-line applications easier.

public class TheTest {
  @Rule
  public final TextFromStandardInputStream systemInMock
    = emptyStandardInputStream();
  @Rule
  public final SystemOutRule systemOutRule
    = new SystemOutRule().enableLog();

  @Test
  public void testAddPaperConfirm() {
    systemInMock.provideLines("P", "The Life of Geoff the Platypus");
    testReviewSystem.main(new String[] {});
    String output = systemOutRule.getLogWithNormalizedLineSeparator();
    assertEquals(output, "What do you want to do?\n" +
        "O = Overview, P = Add Paper, R = Add Review, [num] = Detail of that paper, X = exit\n" +
        "What is the title of the paper?\n" +
        "[Paper added]\n"
        + "What do you want to do?\n" +
        "O = Overview, P = Add Paper, R = Add Review, [num] = Detail of that paper, X = exit\n");
  }
}