Invariants can be used to perform tests on the current state
addInvariant(String description, Condition condition)
addInvariant(String description, Condition condition, Condition...preConditions)
Use the generic conditions
addInvariant("No error messages", new NotRegexCondition("Error [0-9]+");
Create your own condition
crawler.addInvariant("Test count myList", new ConditionAbstract(){ @Override public boolean check(EmbeddedBrowser browser) { WebDriver driver = browser.getDriver(); try{ WebElement myList = driver.findElement(By.id("myList")); return new Select(myList).getOptions().size() > 0; }catch(NoSuchElementException e){ //not found return true; } } });