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Lean BDD with Documentation Generation

FSharp, Gherkin, HTML

Behavior driven development (BDD) and the Gherkin language, first and foremost, are about collaboration and documentation.

The key idea is to specify the behavior of a software system by describing its features using concrete scenarios and examples. By describing the scenarios in the language of the domain and by doing this together with the domain experts, we ensure that each feature is completely covered by its scenarios and that each scenario is specified correctly.

Using this approach ensures that we build the right system.

We write the scenarios using the Gherkin language which is designed to be both, human and machine readable. By parsing the scenarios and automating its steps we turn the specification into executable test cases which verify that the implemented features behave as specified.

Using this approach ensures that we build the system right.

Now, reading raw Gherkin in an IDE is fine when developing and reviewing a particular feature and its scenarios. But when it comes to providing a long term specification, HTML has clear benefits over Gherkin with respect to readability of the scenarios and navigation between features.

For this reason I have added support for generating HTML documentation from Gherkin based feature files to the TickSpec extension TickSpec.Build.

Generating HTML documentation

To generate the HTML documentation run the following command:

TickSpec.Build doc ./src ./html

The first folder specifies the root of the source tree which should be searched for *.feature files. The second folder specifies the location where the HTML files should be generated to.

You can safely specify the root to your complete code base, as folders containing build artifacts like obj and node_modules are ignored.

The command will generate a separate HTML file for each feature file. The Visual Studio project local folder structure will be preserved. Each HTML file intentionally only contains a HTML fragment of type <article/> so that these articles can easily be integrated in an existing HTML page.

Each article is organized in different sections which provide dedicated CSS classes for styling. Checkout the TickSpec.Build documentation for a complete list of available CSS classes.

You can use the command line option --toc html to get a table of contents generated as a standalone HTML page. This option will also add a reference to a CSS stylesheet to each article which can be used for defining the CSS classes mentioned above. This stylesheet needs to be named style.css and has to be located next to the generated table of contents file.

Alternatively you can use the command line option --toc json to get a table of contents generated as a JSON document which can then be used for integrating the generated HTML articles into an existing HTML documentation or web page.

Integration using Vue

Personally, I use this HTML generation feature in one of my projects to integrate the BDD specification into an existing web application based on Vue.JS.

Therefore I configure webpack to load the generated HTML articles as raw text files by adding the following configuration to the vue.config.js:

  configureWebpack: {
    module: {
      rules: [
          test: /\.html$/,
          include: [
            path.resolve(__dirname, "src/assets/spec")
          loader: 'raw-loader'

Next, I created a dedicated Vue component to render the specification including the table of contents read from the JSON document and some basic search support.

      <h2>Table of Contents</h2>

      <input type="text" v-model="search" placeholder="Search ..."/>

      <span v-if="!articles.length">No Results Found.</span>

      <div v-else v-for="(article, index) in articles"
           :key="'article_' + index + Math.random()">
        <a @click="selected = article"></a>

      <div v-html="selected?.html" />

  import toc from '@/assets/spec/toc.json'
  export default {
    name: 'BackLookSpecs',
    data () {
      return {
        search: '',
        selected: null,
        store: []
    computed: {
      articles () {
          .filter(item => {
            return item.title.toLowerCase().includes( ||
          .sort((a, b) => a.path < b.path ? 1 : 0)
    created () {
      const specFiles = require.context('@/assets/spec', true, /\.html/)
      const tocIndex = new Map( => ['./' + x.folders.concat([x.filename]).join('/'), x])) = specFiles.keys()
        .map((x) => {
          const tocEntry = tocIndex.get(x)
          return {
            path: tocEntry.folders.concat([tocEntry.title]).join('/'),
            html: specFiles(x).default

  .gherkin-keyword {
    color: blue;

  .gherkin-tags {
    font-weight: bold;
    padding-right: 5px

MsBuild integration

TickSpec.Build also supports basic MsBuild integration for the HTML documentation generation feature which is described in the project documentation.

In my particular project I have multiple Visual Studio projects containing BDD feature files and I have one specific Visual Studio project which hosts the help system of the web application. In this web project I have integrated the HTML documentation generation for all the feature files in the following way:

<Project Sdk="Microsoft.NET.Sdk.Web">



  <!-- all the other content not relevant for this post -->

    <PackageReference Include="TickSpec.Build" Version="2.8.0" />

  <Target Name="ClearSpecs" BeforeTargets="GenerateFeatureFileHtml">
      <FilesToDelete Include="$(FeatureFileHtmlOutput)\**\*.html"/>
    <Delete Files="@(FilesToDelete)" />  



Using this approach I can now publish my system specification with improved readability and easy to use navigation features to the users of my application. Of course this specification does not replace a real user manual but it definitively can serve as a reference in case of specific questions on how the system behaves.


Tags: Testing