Comparing two TreeMaps with JUnit

Question

Trying to test that two TreeMaps are the same with the following code:

public class StreamTest {

  private Stream stream;
  private Map<String, AtomicInteger> map = new HashMap<>();

  @Before
  public void setup() {
    stream = new Stream();
    map.put("this", new AtomicInteger(1));
    map.put("is", new AtomicInteger(1));
    map.put("an", new AtomicInteger(1));
    map.put("just", new AtomicInteger(1));
    map.put("example", new AtomicInteger(1));
    map.put("file", new AtomicInteger(1));
    map.put("for", new AtomicInteger(1));
    map.get("this").incrementAndGet();
    map.put("project", new AtomicInteger(1));
  }

  @Test
  public void lineToWordsToMapTest() {
    stream.getLines("testSampleFile");
    Map<String, AtomicInteger> sortedmap = new TreeMap<>(stream.getMap());
    Map<String, AtomicInteger> treemap = new TreeMap<>(map);  // Maps must be sorted in order to pass test
    Assert.assertEquals(treemap, sortedmap);
  }

}

And this is the puzzling error message:

java.lang.AssertionError: expected: java.util.TreeMap<{an=1, example=1, file=1, for=1, is=1, just=1, project=1, this=2}> but was: java.util.TreeMap<{an=1, example=1, file=1, for=1, is=1, just=1, project=1, this=2}>
Expected :java.util.TreeMap<{an=1, example=1, file=1, for=1, is=1, just=1, project=1, this=2}> 
Actual   :java.util.TreeMap<{an=1, example=1, file=1, for=1, is=1, just=1, project=1, this=2}>

So the objects look like they are exactly the same using JUnit 4.12. Any insight would be appreciated.

Answer 1

That's because AtomicInteger doesn't override equals() and can't be successfully compared with other instance of AtomicInteger of the same value. You either need to change your map value type or write your own assertion for AtomicInteger.

To simplify:

Assert.assertEquals(new AtomicInteger(1), new AtomicInteger(1));

Results in:

java.lang.AssertionError: expected: java.util.concurrent.atomic.AtomicInteger<1> but was: java.util.concurrent.atomic.AtomicInteger<1>
Expected :java.util.concurrent.atomic.AtomicInteger<1> 
Actual   :java.util.concurrent.atomic.AtomicInteger<1>