add tests for zero elements of monoids

toxyduck · toxyduck · commit a6a0d21d6acc · 2019-10-21T19:25:49.000+03:00
diff --git a/core/src/test/java/fj/MonoidTest.java b/core/src/test/java/fj/MonoidTest.java
@@ -40,4 +40,21 @@ public void union_monoid_test() {
     assertThat(actual, is(Set.set(Ord.intOrd, 1, 2, 3, 4, 5, 6)));
   }
 
+  @Test
+  public void intersection_monoid_zero_test() {
+    Bounded<Integer> integersBounded = Bounded.bounded(0, 10);
+    Monoid<Set<Integer>> monoid = Monoid.setIntersectionMonoid(integersBounded, Enumerator.intEnumerator, Ord.intOrd);
+    Set<Integer> set = Set.set(Ord.intOrd, 1, 2, 3, 4);
+    Set<Integer> zero = monoid.zero();
+    assertThat(monoid.sum(zero, set), is(set));
+  }
+
+  @Test
+  public void union_monoid_zero_test() {
+    Monoid<Set<Integer>> monoid = Monoid.setMonoid(Ord.intOrd);
+    Set<Integer> set = Set.set(Ord.intOrd, 1, 2, 3, 4);
+    Set<Integer> zero = monoid.zero();
+    assertThat(monoid.sum(zero, set), is(set));
+  }
+
 }
