Hamcrest matchers for a List<Set<String>>

Question

I am trying to write a JUnit test for a method that returns

List<Set<String>> result = build(List<Account> accounts, List<Order> orders);

I can check that I have the expected number of entries with

assertThat(result, hasSize(2));

But I'm struggling to find clear documentation on how to write an assert that the list contains one entry with a set size of 2 and one entry with a set size of 4. If someone could point me to the relevant documentation that I need to read, I would be grateful

Answer 1

I don't recall Hamcrest having anything for this particular setup.

I would just test one of the sets for size and then ensure the sum is 6

Using hamcrest-2.2.jar from hamcrest.org and JUnit4 this fails in the 3rd assertThat, since I deliberately created it to fail with an expected value of 5. The test reports no failure when set to 6:

import static org.hamcrest.Matchers.*;
import static org.hamcrest.MatcherAssert.assertThat;

import org.junit.Test;

import java.util.List;
import java.util.Set;

public class MyListTest {

  @Test
  public void listSize() {
    MyList tester = new MyList();
    List<Set<String>> result = tester.generate();

    // assert statements
    assertThat(result, hasSize(2));                                        // yours
    assertThat(result.get(0), anyOf(hasSize(2), hasSize(4)));              // is either 2 or 4
    assertThat((result.get(0).size() + result.get(1).size()), equalTo(5)); // sum must be 6. FAILS with 5 :)
  }
}

Tested class:

import java.util.List;
import java.util.Set;

public class MyList {
  public List<Set<String>> generate() {
    Set<String> s1 = Set.of("Hello", "World");
    Set<String> s2 = Set.of("Testing", "One", "Two", "Three");
    return List.of(s1,s2);
  }
}