'Flat' implementation of the service navigation component

__tests__/mobile-navigation-section.test.js

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+const { goTo, getAttribute } = require('./helpers/puppeteer.js')
+
+describe('MobileNavigationSection', () => {
+  beforeEach(async () => {
+    await page.setViewport({ width: 375, height: 667 })
+  })
+
+  describe('when JavaScript is unavailable or fails', () => {
+    beforeEach(async () => {
+      await page.setJavaScriptEnabled(false)
+
+      await goTo(page, '/')
+    })
+
+    it('does not render the `<button>`s that toggle sections', async () => {
+      await goTo(page, '/')
+
+      await expect(
+        page.$$('.govuk-service-navigation__link button')
+      ).resolves.toStrictEqual([])
+    })
+
+    it('does not render the sub navigation items', async () => {
+      await expect(
+        page.$$('.govuk-service-navigation__link ul')
+      ).resolves.toStrictEqual([])
+    })
+  })
+
+  describe('when JavaScript is available', () => {
+    beforeEach(async () => {
+      await page.setJavaScriptEnabled(true)
+
+      await goTo(page, '/')
+    })
+
+    describe('Initial state', () => {
+      it('adds a `<button>` to each Service Navigation items with the same label as its link', async () => {
+        const $serviceNavigationItems = await page.$$(
+          '.govuk-service-navigation__item'
+        )
+
+        for (const $serviceNavigationItem of $serviceNavigationItems) {
+          const [linkLabel, buttonLabel] =
+            await $serviceNavigationItem.evaluate((el) => {
+              return [
+                el.querySelector('a').textContent,
+                el.querySelector('button')?.textContent
+              ]
+            })
+
+          expect(buttonLabel.trim()).toBe(linkLabel.trim())
+        }
+      })
+
+      it('adds the sub navigation to each Service Navigation items', async () => {
+        const $serviceNavigationItems = await page.$$(
+          '.govuk-service-navigation__item'
+        )
+
+        for (const $serviceNavigationItem of $serviceNavigationItems) {
+          await expect($serviceNavigationItem.$('ul')).resolves.not.toBeNull()
+        }
+      })
+    })
+
+    describe('User interactions', () => {
+      it("toggles the sub navigation when clicking on an item's button", async () => {
+        // Open the service navigation so Puppeteer can click on elements inside it
+        const $navigationToggler = await page.$(
+          '.govuk-js-service-navigation-toggle'
+        )
+        await $navigationToggler.click()
+
+        const $serviceNavigationItem = await page.$(
+          '.govuk-service-navigation__item'
+        )
+
+        const $subNavigation = await $serviceNavigationItem.$('ul')
+        const $button = await $serviceNavigationItem.$('button')
+
+        await $button.click()
+
+        await expect(getAttribute($button, 'aria-expanded')).resolves.toBe(
+          'true'
+        )
+        await expect(getAttribute($subNavigation, 'hidden')).resolves.toBeNull()
+
+        await $button.click()
+
+        await expect(getAttribute($button, 'aria-expanded')).resolves.toBe(
+          'false'
+        )
+        await expect(getAttribute($subNavigation, 'hidden')).resolves.toBe('')
+      })
+    })
+
+    describe('Responsiveness', () => {
+      it('hides the link from the service navigation when the viewport is narrow', async () => {
+        const $serviceNavigationItems = await page.$$(
+          '.govuk-service-navigation__item'
+        )
+
+        // await jestPuppeteer.debug();
+
+        for (const $serviceNavigationItem of $serviceNavigationItems) {
+          const [
+            linkHiddenAttribute,
+            buttonHiddenAttribute,
+            subnavHiddenAttribute
+          ] = await $serviceNavigationItem.evaluate((el) => [
+            el
+              .querySelector('.govuk-service-navigation__link')
+              .getAttribute('hidden'),
+            el.querySelector('button').getAttribute('hidden'),
+            el.querySelector('ul').getAttribute('hidden')
+          ])
+
+          expect(linkHiddenAttribute).toBe('')
+          expect(buttonHiddenAttribute).toBeNull()
+          expect(subnavHiddenAttribute).toBe('')
+        }
+      })
+
+      it('hides the sub navigation and its toggle when the viewport becomes large enough', async () => {
+        await page.setViewport({ width: 1024, height: 768 })
+        // Wait a little bit that the Media Query List reacting to the change of viewport
+        // has triggered its 'change' event before we look at the page
+        await page.waitForSelector(
+          '.govuk-service-navigation__link:not([hidden])'
+        )
+
+        const $serviceNavigationItems = await page.$$(
+          '.govuk-service-navigation__item'
+        )
+
+        for (const $serviceNavigationItem of $serviceNavigationItems) {
+          const [
+            linkHiddenAttribute,
+            buttonHiddenAttribute,
+            subnavHiddenAttribute
+          ] = await $serviceNavigationItem.evaluate((el) => [
+            el
+              .querySelector('.govuk-service-navigation__link')
+              .getAttribute('hidden'),
+            el.querySelector('button').getAttribute('hidden'),
+            el.querySelector('ul').getAttribute('hidden')
+          ])
+
+          expect(linkHiddenAttribute).toBeNull()
+          expect(buttonHiddenAttribute).toBe('')
+          expect(subnavHiddenAttribute).toBe('')
+        }
+
+        await page.setViewport({ width: 375, height: 667 })
+        // Wait a little bit that the Media Query List reacting to the change of viewport
+        // has triggered its 'change' event before we look at the page
+        await page.waitForSelector('.govuk-service-navigation__link[hidden]')
+
+        for (const $serviceNavigationItem of $serviceNavigationItems) {
+          const [
+            linkHiddenAttribute,
+            buttonHiddenAttribute,
+            subnavHiddenAttribute
+          ] = await $serviceNavigationItem.evaluate((el) => [
+            el
+              .querySelector('.govuk-service-navigation__link')
+              .getAttribute('hidden'),
+            el.querySelector('button').getAttribute('hidden'),
+            el.querySelector('ul').getAttribute('hidden')
+          ])
+
+          expect(linkHiddenAttribute).toBe('')
+          expect(buttonHiddenAttribute).toBeNull()
+          expect(subnavHiddenAttribute).toBe('')
+        }
+      })
+
+      it('keeps the open sections open when the viewport is resized', async () => {
+        // Navigate to a page where a section will be open
+        await goTo(page, '/components/')
+
+        const $buttonOfOpenSection = await page.$(
+          '.govuk-service-navigation__item--active button'
+        )
+        const $subnavOfOpenSection = await page.$(
+          '.govuk-service-navigation__item--active ul'
+        )
+
+        await expect(
+          getAttribute($subnavOfOpenSection, 'hidden')
+        ).resolves.toBeNull()
+        await expect(
+          getAttribute($buttonOfOpenSection, 'aria-expanded')
+        ).resolves.toBe('true')
+
+        await page.setViewport({ width: 1024, height: 768 })
+        // Wait a little bit that the Media Query List reacting to the change of viewport
+        // has triggered its 'change' event before we look at the page
+        await page.waitForSelector(
+          '[data-module="app-mobile-navigation-section"]:not([hidden])'
+        )
+
+        await expect(
+          getAttribute($subnavOfOpenSection, 'hidden')
+        ).resolves.toBe('')
+        // Button remains expanded as it's hidden anyways
+        await expect(
+          getAttribute($buttonOfOpenSection, 'aria-expanded')
+        ).resolves.toBe('true')
+
+        await page.setViewport({ width: 375, height: 667 })
+        // Wait a little bit that the Media Query List reacting to the change of viewport
+        // has triggered its 'change' event before we look at the page
+        await page.waitForSelector(
+          '[data-module="app-mobile-navigation-section"][hidden]'
+        )
+
+        // When viewport is narrow again, the subnav is visible like it was before the viewport got larger
+        await expect(
+          getAttribute($subnavOfOpenSection, 'hidden')
+        ).resolves.toBeNull()
+        await expect(
+          getAttribute($buttonOfOpenSection, 'aria-expanded')
+        ).resolves.toBe('true')
+      })
+    })
+
+    describe('On a section root', () => {
+      beforeEach(async () => {
+        await goTo(page, '/components/')
+      })
+
+      it('keeps sub-navigation in the active section open', async () => {
+        const $serviceNavigationItem = await page.$(
+          '.govuk-service-navigation__item--active'
+        )
+
+        const $button = await $serviceNavigationItem.$('button')
+        const $subNavigation = await $serviceNavigationItem.$('ul')
+
+        await expect(getAttribute($button, 'aria-expanded')).resolves.toBe(
+          'true'
+        )
+        await expect(getAttribute($subNavigation, 'hidden')).resolves.toBeNull()
+      })
+
+      it('marks the overview as the current link', async () => {
+        const $serviceNavigationItem = await page.$(
+          '.govuk-service-navigation__item--active'
+        )
+
+        const $subNavigationOverviewLink = await $serviceNavigationItem.$(
+          'ul a[href="/components/"]'
+        )
+
+        await expect(
+          getAttribute($subNavigationOverviewLink, 'aria-current')
+        ).resolves.toBe('page')
+      })
+    })
+
+    describe('In a page within a section', () => {
+      beforeEach(async () => {
+        await goTo(page, '/components/button/')
+      })
+
+      it('keeps the active section open', async () => {
+        const $serviceNavigationItem = await page.$(
+          '.govuk-service-navigation__item--active'
+        )
+
+        const $button = await $serviceNavigationItem.$('button')
+        const $subNavigation = await $serviceNavigationItem.$('ul')
+
+        await expect(getAttribute($button, 'aria-expanded')).resolves.toBe(
+          'true'
+        )
+        await expect(getAttribute($subNavigation, 'hidden')).resolves.toBeNull()
+      })
+
+      it('marks the overview as the current link', async () => {
+        const $serviceNavigationItem = await page.$(
+          '.govuk-service-navigation__item--active'
+        )
+
+        const $subNavigationLink = await $serviceNavigationItem.$(
+          'ul a[href="/components/button/"]'
+        )
+
+        await expect(
+          getAttribute($subNavigationLink, 'aria-current')
+        ).resolves.toBe('page')
+      })
+    })
+  })
+})