Chromedriver and/or Chrome are not able to type into an input field and maintain the focus when multiple tests run in parallel.
The test application implemented an input field which selects the text on
focus (focusin). The implementation is documented in the related example
file under src/test/data.
Tests run in parallel using TestNG's parallelism feature. Each thread creates its own Webdriver instance and thus Chrome session. Each test will click and type into the input field. One test is constantly typing into an input field while the other tests are pending. This is just to increase the likeliness of stealing the focus.
Tests may occasionally fail with errors like this:
expected [D4E4M4O4S4T4R4I4N4G4] but found [4O4S4T4R4I4N4G4]
One can observe that some characters are missing at the start of the string. Sometimes more than one test will fail.
The fact that multiple Chrome instances type into input fields at the same time suggests the assumption that each window will steal another window's focus.
Since the application under test is selecting the text on focus the first typed characters get selected with the next character being typed and then erased.
The likeliness of the error can be controlled by two factors, basically
- how many tests run in parallel (three by default, the more the likely)
- wait delay after the click in the
typeAndVerify()method
This MCVE was created to reproduce this error with as little code as possible. The real world application is much more complicated, only three tests run in parallel and the tests do other things as well (e.g. click buttons).
- Java 1.8.0-181
- Chrome 73.0.3683.86
- Chromedriver 73.0.3683.68
- Firefox 65.0
- Geckodriver 0.24.0
- Selenium 3.4.0
- Maven 3.5.4
/home/dev/opt/jdk8/bin/java \
-Dwebdriver.chrome.driver=/home/dev/opt/selenium/drivers/chrome/chromedriver-73.0.3683.68/chromedriver \
-Dwebdriver.gecko.driver=/home/dev/opt/selenium/drivers/gecko/geckodriver-0.24.0/geckodriver \
-jar /home/dev/opt/selenium/selenium/selenium-server-standalone-3.4.0.jar
The Geckodriver can be omitted when testing against Chrome only.
cd src/test/data/ ; python -m SimpleHTTPServer 8080 ; cd -
/home/dev/opt/maven3/bin/mvn clean test
It might be necessary to run the tests multiple times until a failure occurs.
for n in $( seq 1 10 ); do /home/dev/opt/maven3/bin/mvn clean test; done
You may want to test against Firefox to observe the tests running flawless.
/home/dev/opt/maven3/bin/mvn -Dusegecko=true clean test