TestAuthenticationChain chain = new TestAuthenticationChain();
        chain.loadResult = null;
        User inputUser = createTestUser("inputuser", "Input User");

        User result = chain.load(inputUser);

        assertNull(result);
        assertEquals(1, chain.loadCalls.size());
        assertEquals(inputUser, chain.loadCalls.get(0));
    }

    // Test load with multiple calls

    private final ImmutableMap<E, Integer> inputSet;
    private final int mask;

    SubSet(ImmutableMap<E, Integer> inputSet, int mask) {
      this.inputSet = inputSet;
      this.mask = mask;
    }

    @Override
    public Iterator<E> iterator() {
      return new UnmodifiableIterator<E>() {
        final ImmutableList<E> elements = inputSet.keySet().asList();
        int remainingSetBits = mask;

FIELD com.google.common.collect.ImmutableSet.asList
FIELD com.google.common.collect.JdkBackedImmutableBiMap.inverse
FIELD com.google.common.collect.Maps.FilteredMapValues.unfiltered
FIELD com.google.common.collect.Sets.SubSet.inputSet
FIELD com.google.common.collect.SingletonImmutableBiMap.inverse
FIELD com.google.common.collect.TreeTraverser.PostOrderNode.childIterator
FIELD com.google.common.collect.TreeTraverser.PreOrderIterator.stack