CTA, Metra and Pace want 100 volunteers to test a long-awaited Ventra mobile ticketing app that should launch systemwide by May or June.

Interested riders have until April 3 to apply to be among the select group of 100 initial testers, though the group will eventually expand.

Each agency’s website has a link for volunteers to apply to test the app.

The app will allow CTA users to buy a ticket on an existing Ventra, credit or debit card with five clicks of a smart phone. A Metra ticket purchase will take 12 clicks plus a 13th to activate the ticket at a conductor’s request.

So far, the app has only been tested internally at each agency, and some glitches are still being ironed out.

But at Metra, which has been the slowest to jump onto the Ventra bandwagon, “Everybody we’ve shown the app to has been excited, and most people want to get their hands on it now,” said Lynnette Ciavarella, Metra’s Ventra point person.

“We’re very excited about it. It’s been a long time coming.”

CTA, Metra and Pace will select the first 100 volunteers across all three agencies to provide as broad and diverse a window into user experiences as possible.

This “seed group” will start testing the app in April and expand over time, said Mike Gwinn, CTA director of revenue and fare systems.

Volunteers will need a smartphone — an Apple iPhone with an OS7 or higher operating system, or an Android phone with a 4.0 or higher operating system.

Cubic Transportation Systems was paid $2.5 million to develop the app. Cubic’s bumpy rollout of the CTA’s Ventra card has prompted transit agencies to do especially extensive field testing of the Ventra app, officials say.

The app will feature a “trip tool” that tells users who plug in a CTA or Metra destination when upcoming buses or trains will arrive.

CTA buses will be listed over a 30-minute period; L trains over a 20-minute one. The next five Metra trains will be posted, but users also can plug in a different date to get future train schedules.

By early 2016 the app also should offer access to the RTA Trip Planner and navigation help across all three transit systems.

The Ventra app will allow users to easily view the transit value of their Ventra cards on their smartphones. And they can add between $1 and $100 to their Ventra cards or load a variety of CTA and Metra fare products onto them.

“This is basically a vending machine in your pocket,” said Tony Coppoletta, CTA manager of external electronic communications.

Users also can set up the app to automatically notify them if their Ventra card transit value falls below $10, has expired, or is running a negative balance.

Multiple app accounts also are possible. They could be used, for example, to load up one-day passes before out-of-town guests arrive. Or parents can set up and monitor a student account for children who use public transit to get to school.

Said Gwinn: “We want people to not just be users, but to love using this app.”