code: public void until(@Nonnull Callable<Boolean> shouldBeTrue) {
          until(new RunnableAssert(shouldBeTrue.toString()) {
              @Override
              public void run() throws Exception {
                  assertTrue(shouldBeTrue.call());
              }
          });
      }
docs: Repetitively executes the given <code>Callable&lt;Boolean&gt;</code>
  until it returns <code>true</code> or until the configured
  {@link #timeoutAfter timeout} is reached, in which case an
  {@link AssertionError} will be thrown. Calls {@link Thread#sleep}
  before each retry using the configured {@link #pollEvery interval}
  to free the CPU for other threads/processes.
  
  @since 2.0