Fill the email of a guest in the shipping step of the checkout and wait until the store has checked whether an account uses it.
Examples
When I fill in the checkout email with "guest@example.com"
When I fill in the checkout email with "gail.guest@example.com"
And I fill in the checkout email with "buyer@example.com"
When we fill in the checkout email with "guest@example.com"
When fill in the checkout email with "someone@example.com"
Pattern
When(/^(I |we )*fill in the checkout email with "([^"]*)"$/, …)
Part of @webship-js/magento-steps (github.com/webship/magento-steps), a step pack for Webship-js 2.0.x.