CucumberJVM: DataTable asMap() and asMaps()

What I learned today — 15 May 2018

Cucumber is a really nice tool for specification-by-example acceptance tests. The DataTable provides a convenient way supply parameters in a tabular format.

For brevity I’m going to use Kotlin data classes to define the DTO’s in the following examples:

The simple use of DataTable is to use headings that match the fields on a DTO.

Given the following cities exist:
  | name         | province      | mayor             |
  | Johannesburg | Gauteng       | Herman Mashaba    |
  | Cape Town    | Western Cape  | Patricia de Lille |
  | Durban       | Kwazulu-Natal | Zandile Gumede    |

Letting Cucumber map that to a list of cities in the step definition is easy:

A DataTable can also contain two columns representing a single object.

When a city is updated:
  | name     | Cape Town    |
  | province | Western Cape |
  | mayor    | vacant       |

These values can be read using the DataTable#asMap() method, which interprets the first column as keys and the second column as values.

A DataTable with multiple rows can also be interpreted as a list of maps, using DataTable#asMaps(). This could be useful, for example, if you wish to decouple your glue code (step definitions) from objects used in production code.

Then the cities have the following state:
  | name         | province      | mayor             |
  | Johannesburg | Gauteng       | Herman Mashaba    |
  | Cape Town    | Western Cape  | vacant            |
  | Durban       | Kwazulu-Natal | Zandile Gumede    |

In the step definition map each row (a map with the header row as keys and the row values as values) to the object of your choice:

One may also use these methods if Cucumber is unable to map the fields to the correct type on the DTO shown in the simple example.

Conclusion

I don’t know for how long Patricia de Lille will be able to stay in her office as mayor of Cape Town, but DataTable offers flexible ways to write feature specifications.