JUnit 4 compare Sets

Question

How would you succinctly assert the equality of Collection elements  specifically a Set in JUnit 4

User · Answer

If you want to check whether a List or Set contains a set of specific values (instead of comparing it with an already existing collection), often the toString method of collections is handy:

String[] actualResult = calltestedmethod();
assertEquals("[foo, bar]", Arrays.asList(actualResult).toString());

List otherResult = callothertestedmethod();
assertEquals("[42, mice]", otherResult.toString());

This is a bit shorter than first constructing the expected collection and comparing it with the actual collection, and easier to write and correct.

(Admittedly, this is not a particularily clean method, and can't distinguish an element "foo, bar" from two elements "foo" and "bar". But in practice I think it's most important that it's easy and fast to write tests, otherwise many developers just won't without being pressed.)

User · Answer

As an additional method that is array based     you can consider using unordered array assertions in junitx    Although the Apache CollectionUtils example will work  there is a pacakge of solid assertion extensions there as well      I think that the   ArrayAssert assertEquivalenceArrays new Integer   1 2 3   new Integer   1 3 2      approach will be much more readable and debuggable for you  all Collections support toArray    so it should be easy enough to use the ArrayAssert methods    Of course the downside here is that  junitx is an additional jar file or maven entry                lt dependency org  junit-addons  name  junit-addons  rev  1 4   gt

User · Answer

Apache commons to the rescue again   assertTrue CollectionUtils isEqualCollection coll1  coll2      Works like a charm  I don t know why but I found that with collections the following assertEquals coll1  coll2  doesn t always work  In the case where it failed for me I had two collections backed by Sets  Neither hamcrest nor junit would say the collections were equal even though I knew for sure that they were  Using CollectionUtils it works perfectly

User · Answer

You can assert that the two Sets are equal to one another  which invokes the Set equals   method   public class SimpleTest        private Set lt String gt  setA      private Set lt String gt  setB        Before     public void setUp             setA   new HashSet lt String gt             setA add  Testing               setB   new HashSet lt String gt             setB add  Testing                   Test     public void testEqualSets             assertEquals  setA  setB              This  Test will pass if the two Sets are the same size and contain the same elements

User · Answer

I like the solution of Hans-Peter St  rr    But I think it is not quite correct  Sadly containsInAnyOrder does not accept a Collection of objetcs to compare to  So it has to be a Collection of Matchers   assertThat set1  containsInAnyOrder set2 stream   map IsEqual  equalTo  collect toList        The import are   import static java util stream Collectors toList  import static org hamcrest Matchers containsInAnyOrder  import static org junit Assert assertThat

User · Answer

with hamcrest   assertThat s1  is s2      with plain assert   assertEquals s1  s2     NB t the equals   method of the concrete set class is used

User · Answer

Check this article  One example from there    Test   public void listEquality           List lt Integer gt  expected   new ArrayList lt Integer gt           expected add 5          List lt Integer gt  actual   new ArrayList lt Integer gt           actual add 5          assertEquals expected  actual

User · Answer

Using Hamcrest   assertThat  set1  both everyItem isIn set2    and containsInAnyOrder set1       This works also when the sets have different datatypes  and reports on the difference instead of just failing

User · Answer

A particularly interesting case is when you compare      java util Arrays ArrayList lt   name value type    name1 value1 type1   gt     and     java util Collections UnmodifiableCollection lt   name value type    name1 value1 type1   gt    So far  the only solution I see is to change both of them into sets  assertEquals new HashSet lt CustomAttribute gt  customAttributes   new HashSet lt CustomAttribute gt  result getCustomAttributes        Or I could compare them element by element

[java] JUnit 4 compare Sets

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