Adds more checkInvariants() calls.

Author: brianburton

src/main/java/org/javimmutable/collections/hash/hamt/HamtBranchNode.java

@@ -340,6 +340,9 @@ public void checkInvariants()
                 throw new IllegalStateException();
             }
         }
+        for (HamtNode<T, K, V> child : children) {
+            child.checkInvariants();
+        }
     }
 
     private Indexed<SplitableIterable<T>> indexedForIterator()

src/test/java/org/javimmutable/collections/hash/JImmutableHashMapTest.java

@@ -125,8 +125,8 @@ public void testRandom1()
                 case 4:
                     key = random.nextInt(maxKey);
                     assertEquals(expected.get(key), map.find(key).getValueOrNull());
-
                     assertEquals(expected.size(), map.size());
+                    map.checkInvariants();
                 }
             }
 

src/test/java/org/javimmutable/collections/hash/hamt/HamtBranchNodeTest.java

@@ -326,6 +326,7 @@ public void testRandom()
                 node = node.assign(transforms, key, key, key, size);
                 assertEquals(node.getValueOr(transforms, key, key, -1), node.find(transforms, key, key).getValueOr(-1));
             }
+            node.checkInvariants();
             verifyIntContents(transforms, node, domain);
 
             final MutableDelta zero = new MutableDelta();
@@ -336,6 +337,7 @@ public void testRandom()
                 assertEquals(null, node.getValueOr(transforms, key, key, null));
                 assertEquals(null, node.find(transforms, key, key).getValueOr(null));
             }
+            node.checkInvariants();
             assertSame(HamtEmptyNode.of(), node);
             assertEquals(0, size.getValue());
             assertEquals(0, zero.getValue());