Unpredictable behaviour with Selenium and jUnit - selenium

Question

I am working on a website and trying to test it with Selenium and jUnit. I'm getting race conditions between the test and the site, despite my best efforts.
The front end of the site is HTML and jQuery. The back end (via AJAX) is PHP.
The site
I have two required text input fields (year and age), plus some others that I'm not changing in the tests that give problems. As soon as both text inputs are non-empty, an AJAX call is made to the back end. This will return 0+ results. If 0 results are returned, a results div on the screen gets some text saying that there were no results. If >0 results are returned, a table is written to the results div showing the results.
I don't want the site to wait until e.g. 4 digits' worth of year is entered before doing the AJAX call as it could be looking at ancient history (yes, really). So, as soon as both are non-empty the call should be made. If you type slowly, this means that entering e.g. 2015 will trigger calls for year=2, year=20, year=201 and year=2015. (This is OK.)
The test
I'm using page objects - one for the inputs and one for the output. At the start of the test, I wait for a prompt to be present on the screen (please enter some data) as that is generated by JavaScript that checks the state of the input fields - so I know that the page has loaded and JavaScript has run.
The wait for a prompt is made immediately after the page object is created for the output. This is the relevant method in the page object:
// Wait until the prompt / help text is displayed. Assumes that the prompt text always contains the word "Please"
public void waitForText() {
wait.until(ExpectedConditions.textToBePresentInElementLocated(By.id("resultContainer"), "Please"));
}
The method for setting the year is
public void setYear(String year){
WebElement yearField = driver.findElement(By.id(yearInputId));
if (yearField == null) {
// This should never happen
Assert.fail("Can't find year input field using id " + yearInputId);
} else {
yearField.sendKeys(new String [] {year});
driver.findElement(By.id(ageInputId)).click(); // click somewhere else
}
}
and there's a corresponding one for age.
I have a series of methods that wait for things to happen, which don't seem to have prevented the problem (below). These do things like wait for the current result values to be different from a previous snapshot of them, wait for a certain number of results to be returned etc.
I create a driver for Chrome as follows:
import org.openqa.selenium.chrome.ChromeDriver;
// ...
case CHROME: {
System.setProperty("webdriver.chrome.driver", "C:\\path\\chromedriver.exe");
result = new ChromeDriver();
break;
}
The problem
Some of the time, things work OK. Some of the time, both inputs are filled in with sensible values by the test, but the "there are 0 results" message is displayed. Some of the time, the test hangs part-way through filling in the inputs. It seems to be fine when I'm testing with Firefox, but Chrome often fails.
The fact that there is unpredictable behaviour suggests that I'm not controlling all the things I need to (and / or my attempts to control things are wrong). I can't see that I'm doing anything particularly weird, so someone must have hit these kinds of issue before.
Is there a browser issue I'm not addressing?
Is there something I'm doing wrong in setting the values?
Is there something I'm doing wrong in my test choreography?

Answer 1

It could be that when you start typing, the script is still loading or that there's a pending Ajax call when you start handling the next field or validation.
You could try to synchronize the calls with a low level script :
const String JS_WAIT_NO_AJAX =
"var callback = arguments[0]; (function fn(){ " +
" if(window.$ && window.$.active == 0) " +
" return callback(); " +
" setTimeout(fn, 60); " +
"})();";
JavascriptExecutor js = (JavascriptExecutor)driver;
driver.manage().timeouts().setScriptTimeout(20, TimeUnit.SECONDS);
js.executeAsyncScript(JS_WAIT_NO_AJAX);
driver.findElement(By.Id("...")).sendKeys("...");
js.executeAsyncScript(JS_WAIT_NO_AJAX);
driver.findElement(By.Id("...")).click();