Add A/B testing to your Next.js website

Set the API request headers

Since the API request headers are already prepared, you can simply set the API request headers for your page. To set the API request headers, update your page.tsx with the highlighted code below:

// Import the section components to display them 
import HeroSection from "@/components/sections/hero-section";
import FeatureSection from "@/components/sections/feature-section";
import {getClient} from "@/apollo-client";
import {GetPageBySlugDocument, GetPageBySlugQuery} from "@/gql/graphql";
import {notFound} from "next/navigation";
import { getPreprHeaders } from '@preprio/prepr-nextjs'
 
export const revalidate = 0
export const dynamic = 'force-dynamic'
 
async function getData(slug: string) {
  const {data} = await getClient().query<GetPageBySlugQuery>({
    query: GetPageBySlugDocument,
    variables: {
        slug: slug,
    },
    context: {
      // Call the getPreprHeaders function to get the appropriate headers
      headers: await getPreprHeaders()
    },
    fetchPolicy: 'no-cache',
  })
 
    if (!data.Page) {
        return notFound()
    }
 
    return data
}
 
export default async function Page({ params}: {params: Promise<{ slug: string | string[]}>}) 
{
    let { slug} = await params
 
    // Set the slug to the home page value if there's no slug 
    if (!slug) {
        slug = '/'
    }
 
    // Add a forward slash to the slug to navigate to the correct page.
    if (slug instanceof Array) {
        slug = slug.join('/')
    }
 
    const data = await getData(slug)
    const elements = data.Page?.content.map((element, index) => {
      if (element.__typename === 'Feature') {
          return <FeatureSection key={index} item={element}/>
      } else if (element.__typename === 'Hero') {
          return <HeroSection key={index} item={element}/>
      }
    })
    
    return (
        <div>
          <meta property='prepr:id' content={data.Page?._id}/>
          {elements}
        </div>
    );
}

Test your A/B test

The A/B test is now running in your website. Let's check the traffic distribution for the A/B test.

In your Prepr environment, go to the Electric Lease Landing Page content item and click the icon in your A/B test group and choose the Manage settings option. You'll notice the traffic distribution is set to 50%. This means that about 50% of customers that visit the electric lease landing page will see variant A and about 50% will see variant B.

To test that the A/B test in the electric lease landing page is showing variant A and variant B to different customers, you can pretend to be different customers visiting the page in your browser. Follow the steps below to do this simple test.

1. Go to http://localhost:3000/electric-lease to open the Electric Lease Landing Page in the browser. Take note of the heading in the top section. The text should read either Drive Electric... (Variant A) or Go Electric... (Variant B).

2. Right click the page to Inspect the page, click the Application tab. Under the cookies, click your localhost. You'll notice the __prepr_uid cookie in the list.

3. Right-click the localhost entry to clear the cookies and refresh the page again. If you still see the same variant, repeat the process. You might see the same variant a couple of times in a row.

   

When you see the other variant, you know that the A/B test is running successfully.

Add HTML attributes to track impressions and conversion events

Your A/B test is running successfully, however there are no metrics being recorded yet. You can see this with the Awaiting data message at the top of the A/B test in the Electric Lease Landing Page content item.

To get Prepr to start showing some metrics data, you need to add HTML attributes to elements in your A/B test. When you add these attributes, the tracking code you added in the previous section automatically tracks impressions and your chosen conversion events.

1. To start collecting impressions and clicks, add the HTML attributes data-prepr-variant-key and data-prepr-variant-event to the Hero section as shown in the highlighted code below. The impression is recorded when the Hero element scrolls into view. The click is recorded when the Button element is clicked.

   ./src/components/hero-section.tsx

   import Link from 'next/link'
   import { FragmentType, getFragmentData } from '@/gql'
   import { HERO_SECTION_FRAGMENT } from '@/queries/get-page-by-slug'
   import Image from 'next/image'
   import Button from '@/components/button'
    
   export default function HeroSection(props: { item: FragmentType<typeof HERO_SECTION_FRAGMENT> }) 
   {
       const item = getFragmentData(HERO_SECTION_FRAGMENT, props.item)
       const image = item.image
       
       return ( 
           /* Set the HTML attribute with the matching data-prepr-variant-key to collect impressions for the whole section */
           <section className="bg-primary-50" data-prepr-variant-key={item._context?.variant_key}>
               <div className="mx-auto max-w-8xl p-spacing flex flex-col items-center md:flex-row gap-8 py-10 lg:py-20">
                   <div className="basis-6/12">
                       <h1 className="text-mb-5xl lg:text-7xl text-secondary-700 font-medium break-words text-balance">{item.heading}</h1>
                       <p className="text-mb-lg text-secondary-500 lg:text-lg mt-4 lg:mt-6 text-balance">{item.sub_heading}</p>
                       <div className="flex gap-4 mt-8 xl:mt-10">
                       <div>
                           {/* Set the HTML attribute to collect click events on the link */}
                           <Link href='#' data-prepr-variant-event><Button>Find your car</Button></Link>
                       </div>
                       </div>
                   </div>
                   <div className="basis-6/12 relative flex justify-end items-center">
                       <div className="z-10 flex items-center aspect-[20/17] w-9/12 overflow-hidden justify-center absolute top-1/2 left-1/2 transform -translate-x-1/2 -translate-y-1/2">
                           <Image src={image?.url || ''} alt="Hero Image" width={720} height={360} className='object-cover rounded-2xl'/>
                       </div>
                       <div
                           className="w-9/12 aspect-[20/17] bg-primary-100 rounded-3xl right-0 top-0 z-0">
                       </div>
                   </div>
               </div>
           </section>
       )
   }

2. To start recording metrics, go to the electric lease landing page in your website, in the top section click the Find your car button.

3. Now when you view the A/B test in your Electric Lease Landing Page content item, you can click the Metrics link and see the number of impressions and clicks like in the image below.