fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    ImmutableList<String> result = builder.build();

    /*
     * Maybe it rejects all elements, or maybe it adds "a" before failing.
     * Either way is fine with us.
     */
    if (result.isEmpty()) {
      return;
    }
    assertTrue(ImmutableList.of("a").equals(result));

      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    ImmutableList<String> result = builder.build();

    /*
     * Maybe it rejects all elements, or maybe it adds "a" before failing.
     * Either way is fine with us.
     */
    if (result.isEmpty()) {
      return;
    }
    assertTrue(ImmutableList.of("a").equals(result));