Add ability to test nested children in examples

lib/jest-helpers.js

@@ -15,23 +15,29 @@ nunjucks.configure(configPaths.components, {
 })
 
 /**
- * Render a component's template for testing
+ * Render a component's macro for testing
  * @param {string} componentName
- * @param {string} params parameters that are used in the component template
- * @returns {function} returns cheerio (jQuery) instance of the template for easy DOM querying
+ * @param {string} params parameters that are used in the component macro
+ * @param {any} children any child components or text, pass the children to the macro
+ * @returns {function} returns cheerio (jQuery) instance of the macro for easy DOM querying
  */
-function render (componentName, params) {
+function render (componentName, params, children = false) {
   if (typeof params === 'undefined') {
     throw new Error('Parameters passed to `render` should be an object but are undefined')
   }
 
   const macroName = componentNameToMacroName(componentName)
   const macroParams = JSON.stringify(params, null, 2)
 
-  let macroString = `
-{%- from "${componentName}/macro.njk" import ${macroName} -%}
-{{- ${macroName}(${macroParams}) -}}
-`
+  let macroString = `{%- from "${componentName}/macro.njk" import ${macroName} -%}`
+
+  // If we're nesting child components or text, pass the children to the macro
+  // using the 'caller' Nunjucks feature
+  if (children) {
+    macroString += `{%- call ${macroName}(${macroParams}) -%}${children}{%- endcall -%}`
+  } else {
+    macroString += `{{- ${macroName}(${macroParams}) -}}`
+  }
 
   const output = nunjucks.renderString(macroString)
   return cheerio.load(output)

src/components/fieldset/template.test.js

@@ -108,4 +108,10 @@ describe('fieldset', () => {
     expect($component.attr('data-attribute')).toEqual('value')
     expect($component.attr('data-another-attribute')).toEqual('another-value')
   })
+
+  it('renders nested components using `call`', () => {
+    const $ = render('fieldset', {}, '<div class="app-nested-component"></div>')
+
+    expect($('.govuk-fieldset .app-nested-component').length).toBeTruthy()
+  })
 })