Assert the number of characters a plain text field with a limit still takes, as the counter under the field shows it.
Examples
Then the "Summary" field should have 160 characters left
Then the "Summary" field should have 144 characters left
Then the "Summary" field should have 0 characters left
And the "Summary" field should have 1 character left
Then the "Summary" field should have -5 characters left
Pattern
Then(/^the "([^"]*)" field should have (-?\d+) characters? left$/, …)
Part of @webship-js/craft-cms-steps (github.com/webship/craft-cms-steps), a step pack for Webship-js 2.0.x.