Assembling Gherkin ASTs to feature file string

Usage no npm install needed!

<script type="module">
  import gherkinAssembler from '';



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It allows to convert Gherkin AST to feature file string.



The objectToAST API method converts the given Gherkin object into GherkinDocument object.

A complete sample Gherkin object can be found here: Complete Gherkin object.


  • {Object} documet - a single Gherkin object

Returns: {GherkinDocument}

format(document, options)

The format API method formats the given Gherkin Document(s) to string (which could be written out to feature file(s)).


  • {GherkinDocument|Array<GherkinDocument>} document - a single or multiple Gherkin Documents given in it's AST model.
  • {FormatConfig} options - options to set attributes of formatting.

Returns: {string|Array<string>}

'use strict';

const fs = require('fs');
const assembler = require('gherkin-assembler');
const document = assembler.objectToAST(require('./login.ast.json'));

fs.writeFileSync('./login.feature', assembler.format(document), 'utf8');


By passing an FormatConfig object to format method (or other Ast type methods where it's applicable) it can be set, how feature file text is rendered.

Option Description Default
oneTagPerLine Should tags rendered separately, one by line? false, i.e. all tag of a scenario, feature, etc will be rendered in the same line
separateStepGroups Should step groups (when-then) be separated? false
compact Should empty lines be skipped, removed from the result? false, i.e. there will be empty lines in appropriate places
lineBreak The line break character(s). \n, i.e. it uses Unix line break, to set Windows style, set \r\n
indentation The indentation character(s). ' ', i.e. it uses two space character to add indentation where it's appropriate

Parsing feature files to Gherkin object

Although this package does not contain method to parse feature file to Gherkin object, you can use the gherkin subpackage of CucumberJS.

'use strict';
const fs = require('fs');
const {Parser} = require('gherkin');
const parser = new Parser();
const document = parser.parse(fs.readFileSync('./login.feature'));

// use objectToAST and format to write it to file again