How do I use regular expressions in a Cucumber table (multiline argument) to diff against table?

Question

I am using a scenario table (multiline step arguments) to check some data from a screen using cucumber, using the in built .diff! method on the Cucumber AST table.

I would like to check the content matches against regular expressions.

Scenario: One
    Then the table appears as:
    | One   | Two   | Three |
    | /\d+/ | /\d+/ | /\d+/ |

The actual table could look something like

| One | Two | Three |
| 123 | 456 | 789   |

which this scenario is translated to "as long as there are some digits, I don't care"

An example step implementation that fails:

Then /^the table appears as:$/ do |expected_table|
  actual_table  = [['One','Two', 'Three'],['123', '456', '789']]
  expected_table.diff! actual_table
end

Error:

Then the table appears as: # features/step_definitions/my_steps.rb:230
      | One    | Two    | Three  |
      | /\\d+/ | /\\d+/ | /\\d+/ |
      | 123    | 456    | 789    |
      Tables were not identical (Cucumber::Ast::Table::Different)

I have tried using step transforms to transform the cells into regular expressions, but they still aren't identical.

Transform code:

 expected_table.raw[0].each do |column|
    expected_table.map_column! column do |cell|
      if cell.respond_to? :start_with?
        if cell.start_with? "/"
          cell.to_regexp
        else
          cell
        end
      else
        cell
      end
    end
  end

which provides the eror:

Then the table appears as: # features/step_definitions/my_steps.rb:228
      | One          | Two          | Three        |
      | (?-mix:\\d+) | (?-mix:\\d+) | (?-mix:\\d+) |
      | 123          | 456          | 789          |
      Tables were not identical (Cucumber::Ast::Table::Different)

Any ideas? I am stuck.

Answer 1

Using regular expressions in a scenario is almost certainly the wrong approach. Cucumber features are intended to be read and understood by business-focussed stakeholders.

How about writing the step at a higher level, such as as:

Then the first three columns of the table should contain a digit