Cucumber DataTable

Installation

npm i @cucumber-stories/cucumber-datatable

What is it?

Cucumber DataTable is a library to simplify and enhance data tables in gherkins feature files. By providing schema for your data table you can easily pass from silly strings to structured and typed data.

A sample is better than 100 words:

Imagine you want to handle a gherkin table like this:

Feature: Heroes sample

  Scenario: A simple heroes table
    Given the following heroes
      | Name         | Age |
      | Bruce Wayne  | 83  |
      | Tony Stark   | 52  |
      | Bruce Banner | 53  |

Thanks to @cucumber-stories/cucumber-datatable write this...

import { DataTable } from "@cucumber/cucumber";
import { cucumberDataTable } from "@cucumber-stories/cucumber-datatable";

const getHeroes = cucumberDataTable({
  name: { columnName: "Name", converter: Converters.String },
  age: { columnName: "Age", converter: Converters.Number },
});

Given(/^The following heroes$/, function (dataTable: DataTable) {
  const heroes = getHeroes(dataTable);
  console.log(heroes); // [{ name: 'Bruce Wayne', age: 83 }, ...]
});

...Instead of that

import { DataTable } from "@cucumber/cucumber";

Given(/^The following heroes$/, function (table: DataTable) {
  const lines = data.raw();
  // Here you have an hugly array of string arrays (string[][]) ☹️
});

How to use it?

First, you have to define a dictionary composed of 2 things. It has the same keys as output objects and attach to it the following metadata:

• columnName: The column name in the gherkin file (.feature)
• converter: The converter to use to transform the data from the gherkin data table

You have to use the cucumberDataTable() function to create a reusable function used in your steps to transform your data.

import { cucumberDataTable } from "@cucumber-stories/cucumber-datatable";

const dictionary = {
  name: {
    columnName: "Name", // Column name in Gherkin file
    converter: Converters.String, // Converter to use (more samples below)
  },
  age: {
    columnName: "Age",
    converter: Converters.Number,
  },
};

const getStructuredData = cucumberDataTable(dictionary);

// ....
Given(/^The following table/, function (dataTable: DataTable) {
  const data = getStructuredData(dataTable);
});

Converters

Converters are used to convert the data. Out of the box the library provides some useful converters.

Some of the converters can be configurable, you can have details on the Converter config section.

Converter config

If a converter needs configuration, you can call .withConfig method with the specified configuration, such as:

const dictionary = {
  tags: {
    columnName: "Tags",
    converter: Converters.StringArray.withConfig({
      separator: "-",
    }),
  },
};

Nullable

If some of your values need to be nullable, and want to be used as null in your code, you can use the Nullable converter.

const dictionary = {
  name: {
    columnName: "Name",
    converter: Converters.Nullable(Converters.String),
  },
};

// name will be string | null

You can also configure the null value, which default to <null>

const dictionary = {
  name: {
    columnName: "Name",
    converter: Converters.Nullable(Converters.String, {
      nullValue: "vide",
    }),
  },
};

// name will be string | null, when the value is "vide"

Object array converter

The Converters.ObjectArray() is a bit tricky, so it deserve its own part in our documentation.

Imagine the following gherkin file:

Feature: Heroes sample

  Scenario:
    Given the following attributes
      | Attributes     | Other |
      | 1:Color,2:Size | other |
      | 10:Name        | other |

If you want an output like this:

[
  {
    attributes: [
      { code: 1, name: "Color" },
      { code: 2, name: "Size" },
    ],
    other: "other",
  },
  {
    attributes: [{ code: 10, name: "Name" }],
    other: "other",
  },
];

You probably need the Converters.ObjectArray().

To use this converter you have to define:

• the separator of different items
• the separator of different properties of a same object

And then the schema of nested objects:

import {
  cucumberDataTable,
  Converters,
} from "@cucumber-stories/cucumber-datatable";

const dictionary = {
  attributes: {
    columnName: "Attributes",
    converter: Converters.ObjectArray({
      code: {
        position: 0,
        converter: Converters.Number,
      },
      name: {
        position: 1,
        converter: Converters.String,
      },
    }).withConfig({
      propertySeparator: ":",
      itemSeparator: ",",
    }),
  },
  // Other columns...
  other: {
    columnName: "Other",
    converter: Converters.String,
  },
};

const getStructuredData = cucumberDataTable(dictionary);

You don't have to specify .withConfig if you want to keep the default config which is { propertySeparator: ":", itemSeparator: "," }

Custom converter

To sum up, a converter is an instance of the Converter class. To create a custom converter to answer your need, you have to use Converter.Custom(<Your converter function>).

The converter function takes:

1. a string in argument (the data from the gherkin file),
2. an optional config as a second parameter,
3. and returns what you want.

For example if you want to output a custom structure from a column you can do this:

import {
  cucumberDataTable,
  Converters,
} from "@cucumber-stories/cucumber-datatable";

const dictionary = {
  code: {
    columnName: "Code",
    converter: Converters.Custom((code: string) => ({ nested: code })),
  },
  configurableCode: {
    columnName: "Configurable code",
    converter: Converters.Custom(
      (code: string, config?: { append: string }) => code + config?.append
    ).withConfig({
      append: "-code",
    }),
  },
  // Other columns...
  other: {
    columnName: "Other",
    converter: Converters.String,
  },
};

const getStructuredData = cucumberDataTable(dictionary);

It will transform this table:

Feature: Heroes sample

  Scenario: A simple heroes table
    Given the following table
      | Code | Configurable code | Other |
      | 001  | 001               | other |
      | 002  | 001               | other |

Into:

[
  { code: { nested: "001" }, configurableCode: "001-code", other: "other" },
  { code: { nested: "002" }, configurableCode: "002-code", other: "other" },
];

Development

Running tests

Run npm test and npm run test-types

Publish a new version

1. npm version <major|minor|patch>
2. git push --tags
3. Create a release on this tag.