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index.test.js
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index.test.js
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/* eslint-env jest */
import { join } from 'path'
import {
killApp,
findPort,
nextStart,
nextBuild,
renderViaHTTP,
} from 'next-test-utils'
import fs from 'fs-extra'
jest.setTimeout(1000 * 30)
const appDir = join(__dirname, '../')
const nextConfig = join(appDir, 'next.config.js')
let appPort
let app
function runTests() {
describe('On a static page', () => {
checkImagesOnPage('/')
})
describe('On an SSR page', () => {
checkImagesOnPage('/stars')
})
}
function checkImagesOnPage(path) {
it('should not preload tiny images', async () => {
const html = await renderViaHTTP(appPort, path)
expect(html).not.toContain(
'<link rel="preload" href="tiny-image.jpg" as="image"/>'
)
})
it('should not add a preload if one already exists', async () => {
let html = await renderViaHTTP(appPort, path)
html = html.replace(
'<link rel="preload" href="already-preloaded.jpg" as="image"/>',
''
)
expect(html).not.toContain(
'<link rel="preload" href="already-preloaded.jpg" as="image"/>'
)
})
it('should not preload hidden images', async () => {
const html = await renderViaHTTP(appPort, path)
expect(html).not.toContain(
'<link rel="preload" href="hidden-image-1.jpg" as="image"/>'
)
expect(html).not.toContain(
'<link rel="preload" href="hidden-image-2.jpg" as="image"/>'
)
})
it('should not preload SVG images', async () => {
const html = await renderViaHTTP(appPort, path)
expect(html).not.toContain(
'<link rel="preload" href="vector-image.svg" as="image"/>'
)
})
it('should preload exactly two eligible images', async () => {
const html = await renderViaHTTP(appPort, path)
expect(html).toContain(
'<link rel="preload" href="main-image-1.jpg" as="image"/>'
)
expect(html).not.toContain(
'<link rel="preload" href="main-image-2.jpg" as="image"/>'
)
})
}
describe('Image optimization for SSR apps', () => {
beforeAll(async () => {
await fs.writeFile(
nextConfig,
`module.exports = { experimental: {optimizeImages: true} }`,
'utf8'
)
await nextBuild(appDir)
appPort = await findPort()
app = await nextStart(appDir, appPort)
})
afterAll(() => killApp(app))
runTests()
})
describe('Image optimization for serverless apps', () => {
beforeAll(async () => {
await fs.writeFile(
nextConfig,
`module.exports = { target: 'serverless', experimental: {optimizeImages: true} }`,
'utf8'
)
await nextBuild(appDir)
appPort = await findPort()
app = await nextStart(appDir, appPort)
})
afterAll(() => killApp(app))
runTests()
})