The tool uses techniques like dependency analysis to only test code affected by changes, and parallel test execution to run tests as quickly as possible, according to the Wallaby website.
"It reports code errors with navigable stacks, test expectation errors, code coverage, test execution time and much more." Feedback is delivered to the code editor, to the line of code being edited.
"My major goal was to create a tool that would allow [me as a developer] to get an instant feedback from my tests and right in my editor, just as I type my code, even if I have thousands of tests," said Govorov, who has worked as an independent contractor at JetBrains.
"Existing test runners can either run some manually selected tests or all of the tests, and it may be time-consuming.
Wallaby.js in its turn is using a sophisticated technology to automatically calculate and run the minimal required number of tests affected by your code changes." Wallaby.js, however, can work alongside testing technologies, such as Mocha, Jasmine, and QUnit