Principles of Product Design
05Fast feedback
Product prototyping—accelerated
Listen to Chapterby Aarron Walter
Have you ever watched a great chef at work—the kind of chef worthy of a coveted Michelin Star? Whether she’s in the kitchen, the field, or at the market, she’s always tasting the food. Her palette guides her to the right flavors, aromas, and textures that combine to create an unforgettable meal. The alchemy of great cooking can only happen when the chef gets feedback at each step of her process.
Similarly, design teams that produce great products have something in common—they habitually test their designs. Before a single line of code is written, they build high-fidelity prototypes and put them in the hands of colleagues and customers, collecting fast feedback and correcting course before development.
These product design teams have a huge competitive advantage over those that get feedback only after their product ships: they learn faster. They spot problems quickly and fix them. They talk to customers early and align the product to their needs.
Learning faster
Learning faster means shipping more polished products that attract customers faster.
The software industry isn’t the first to grasp this principle. The animation industry was transformed by an underdog studio in Los Angeles that found a way to learn faster than the big New York studios by getting fast feedback.
Learn fast, leap forward
In the early 20th century, the boundaries of animation had been drawn and the industry was happily operating within them. The medium was crude—settings were flat, characters lacked personality, and the content was often limited to slapstick gags.
Then Walt Disney Studios changed everything.
Disney’s faith in the medium as an artform pushed the studio to experiment with new ideas that lead to astounding technical achievements. In 1928, they introduced sound with the release of Steamboat Willie, and in 1932 they introduced full color with Flowers and Trees. Each is an impressive achievement, but it was the studio’s contributions to process that enabled animation to evolve into the rich medium we know today.
In 1931, seeking faster feedback on their drawings, Disney animators began making what they called “pencil tests:” rough drawings on inexpensive negative film that they fed into the Moviola, a device with a small screen for viewing footage.

Figure 1. Les Clark, one of Walt Disney Studios’ first animators, viewing a quick pencil test through a Moviola.
This process let Disney animators meticulously refine their drawings immediately, not weeks or months later, and enabled them to learn the art of the medium faster than any other studio. Soon the animators began stringing together pencil tests to review entire scenes, the interaction of characters, and the delivery of the story.
In our little studios on Hyperion Street, every foot of rough animation was projected on the screen for analysis, and every foot was drawn and redrawn until we could say, ‘This is the best we can do.
Walt Disney
Disney Studios
Walt Disney Studios’ prototyping method pushed the medium into new territory. While other studios produced silly gag films to make people laugh, Disney created art with emotionally complex characters that made audiences cry.
By building fast feedback into their creative process, Walt Disney Studios was able to make a huge leap. What worked for Disney can work for your design team too. Don’t worry, you won’t need to track down a Moviola on eBay. All you need is a high-fidelity prototype.

Snow White Pencil Test
Walt Disney Studios

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Prototyping and tools
Prototypes let us present product concepts to colleagues and customers without diving into the production process. A good prototype is a balancing act—it feels like a real product, but doesn’t require a lot of time to build.
I used to create prototypes using HTML, CSS, and JavaScript. It was a painful, time-consuming process that affected my judgement when testing. I’d spend a week or more producing a prototype that was vaguely realistic enough to show customers. When feedback called for big changes, I found myself reluctant to act, as the work seemed daunting.
That process seems ridiculous today, as we’re in a golden age of product design tools. We can now create prototypes that are much higher fidelity in less time without writing a single line of code. With less time invested, tweaks to a prototype come easy.
There are a number of prototyping tools on the market—more than we can cover here. Do some research to find the right fit for your needs. As you consider various prototyping tools, ask yourself these questions:
- Is it easy to focus on product design problems, or will I be fiddling with the tool or code?
- Can I deploy my prototype to various devices to create a realistic testing experience?
- If you’re working remotely, is it easy to share the prototype and conduct remote testing?
![Typically, we will go to a higher fidelity [prototype] earlier on in the process.](https://s3.amazonaws.com/designco-web-assets/uploads/2017/06/andy_law_1920px_v4_2.jpg)
Typically, we will go to a higher fidelity [prototype] earlier on in the process.
Andy Law
Netflix
InVision and Sketch
As you might’ve guessed, we’re partial to prototyping with InVision. Before joining InVision, my product design team at MailChimp used InVision to prototype new apps and explore feature concepts. It helped us move fast and get the feedback we needed. We shared InVision prototypes with the engineering team early to get feedback and keep everyone in sync.
Many product designers have transitioned from Photoshop to Sketch, which lets you work on multiple screens in a single file. You can save common UI elements like buttons and forms as shared symbols to build a screen quickly. There are a number of great learning resources to guide you if you’ve yet to make the leap to Sketch.
Craft by InVision, a suite of free plugins for Sketch and Photoshop, creates a tight integration between Sketch and InVision, shortening the prototype design process. It lets you pull real data from an API, fetch content from a site, or grab elegant photos and drop them into your design file to make your UI more realistic. Craft even lets you build a prototype directly in Sketch.
Design tools today are doing for product design what Disney’s pencil tests and the Moviola did for animation—they’re shortening the learning process so the craft can evolve faster.
Keynote
Keynote, Apple’s popular presentation software, has become a go-to prototyping tool for many designers. It’s simple enough that almost anyone can prototype with it, and sophisticated enough to do elegant animations that make a series of images feel like a real app.
Install Keynote on your iPhone or iPad to run prototypes on the target device, making the testing experience more realistic. Design prototypes in Keynote faster with Keynotopia’s UI templates for both iOS and Android. If you end up doing a lot of prototyping, you’ll probably want to take some time to create your own UI template library so you don’t have to continuously apply your brand’s colors and style to stock elements.
UI kits
Faster prototyping with a pattern library
Your product prototyping process can be accelerated exponentially when you work with a pattern library—a collection of standard elements that can be combined like LEGO blocks to create a new UI. Creating a pattern library is time consuming work, but it pays off with the design of each new product or feature.

Figure 2. The InVision design team has built a pattern library that speeds up design and maintains consistency though the team is located around the world.
Facing UI fragmentation across many products and platforms, the design team at NASDAQ revised their schedule to spend time creating a pattern library. The process was intense, but helped them unify the user experience across all of their products. There was an additional benefit they hadn’t initially anticipated—prototyping with a pattern library helped them move very quickly.
Spending less time noodling on UI treatments means designers can focus more on aligning the product to customers’ needs. Companies like Salesforce, IBM, Atlassian, MailChimp, Spotify, and Westpac have all developed detailed design systems that help them design new products quickly.

You can really focus on which parts of the prototype you can bring up to a good level of fidelity.
Daniel Burka
Google Ventures

Team collaboration—in real time
InVision Freehand is your team’s infinite space for fast, flexible collaboration
Getting feedback on your prototype
Testing internally
With your prototype built, you can start collecting feedback. Before you put your prototype in front of customers, spend time talking with your design and engineering colleagues. They’ll help you look at the UI with fresh eyes, and reconnect with the key objectives of the project. Now’s a great time to conduct a design review.
Deploy your prototype to the devices you’ll be targeting so everyone can get a feel for the real experience. It’s not uncommon for designers to walk around the building to grab a few colleagues for an impromptu test of a prototype. Great feedback can come from unexpected places, so look beyond the design and engineering teams.
With feedback in hand, revise your prototype accordingly and get ready to test with real customers.
Testing with customers
You’re going to learn a lot as you show your product prototype to your customers. Your ideas and assumptions will be put to the test, which may at times make you uncomfortable. It can be frustrating to watch users struggle with your design.
Your instincts might lead you to help customers figure out how to use your app, but you’ll taint the feedback if you do. Instead, stick to your testing script or work with a moderator who can conduct the tests impartially.
Michael Margolis, UX Research Partner at GV, follows a very simple process as he conducts tests with customers: a welcome, an ice breaking period, the introduction of the prototype, the test, and a debrief. Michael’s script is wonderfully simple and easy to remember. Dive into his process in more detail in the book Sprint from GV.

When we’re developing new ideas…it’s really valuable to get some fresh eyes and fresh perspective…
Michael Margolis
Google Ventures, from the 5 act interview
Elaborate usability tests are a waste of resources. The best results come from testing no more than 5 users and running as many small tests as you can afford.
Jakob Nielsen
Nielsen Norman Group
According to research conducted by the Nielsen Norman Group, the majority of problems with your prototype will be identified after testing with just 5 customers. Instead of testing more customers, Jakob Nielsen recommends another small batch of tests after refinements have been made.
Recruiting customers
Running the test is actually the easy part of the feedback process. Finding test subjects is the hard part. If you have an existing customer base, query your database to find power users. Devout customers are often excited to see new design concepts, and will likely give more informed feedback. This is their chance to influence the design process!
If you’re testing a prototype for a brand new product, you’ll need to be more creative in how you recruit. Once again, the GV team has a clever solution. They create a form to screen customers that asks a few carefully considered questions. A worksheet guides them to create a screener that will target the right kinds of people. They post a link to their screener form on Craigslist, Twitter, Facebook, and send to an existing mailing list if available. Since you’ll only need about 5 test subjects, you don’t need a high response rate to the screener.
Be prepared to compensate your customers for their time—remember, they’re doing you a big favor by testing your prototype.
Alternatively, you could hire a professional recruiter to find customers for you. The downside is it can be very expensive, and it won’t be a hands-off process. You’ll still need to give them enough information to target the right customers.
When we don’t have a live product built and we need to get feedback, we can send a prototype to researchers to have it tested. It allows us to get feedback not just from drivers in San Francisco but from all around the world.
Molly Nix
Uber
Testing remotely
Not all the customers you recruit will live nearby. You’ll need to make plans to conduct tests remotely too. Gregg Bernstein, Senior User Researcher for Vox Media, has developed an elegant system to conduct tests with users remotely using inexpensive, freely available software—a rig that runs just $99, a small price to pay for fast feedback!
Here’s how he does it:
- Gregg shares a Calendly link with a potential test participant, letting her select a convenient test time. Calendly also lets Gregg ask for permission to record the session, and lets him send details on what the test participant can expect.
- The Vox design team posts a prototype to InVision.
- Gregg invites the participant to Zoom call where the customer can use the prototype while Gregg asks questions, observes, and takes notes.
- The session is recorded using ScreenFlow.
- After the test session is complete, Gregg re-watches the video to fill in gaps in his notes. He then shares those notes and his insights with his Product team via Slack.
This process is simple and fast, yet effective. It lets Vox’s remote product team get feedback from users anywhere without hopping on a plane.
A service like Lookback.io can also help you get fast feedback from both colleagues and customers remotely. InVision and Lookback integrate to let you test a mobile app prototype with customers. It records the customer’s screen, their interactions with your prototype, and even overlays a video of their face as they use your app, helping you read their emotional state.
When your app is built, your developers can integrate Lookback into your app so test sessions can be triggered any time. Users can shake their phone to reveal a secret button that triggers Lookback’s recording feature. All sessions are stored in a central dashboard for designers and developers to review and make revisions.
Lindsey Campbell, UX researcher at InVision, has a unique approach to getting customer feedback remotely. She’s set up a Slack channel to share prototypes with devout customers to get early feedback and bring customers into the design process. The design team monitors the feedback and tweaks the product as needed.
Related: Get stakeholder approval 46% faster
Better, faster product prototyping and testing
Like a chef sampling her ingredients, designers need to get a taste of the user’s experience while designing, not just after the product ships. When you shorten the feedback loop, you can learn faster how to make a product that will appeal to your audience. Here’s some guidance to get you started.
- When should I build a prototype? After you’ve done initial research and worked through many ideas on paper.
- How much of the app should I build in my prototype? Don’t waste time prototyping the entire app. Focus instead on the parts about which you have the most questions.
- How real should my prototype be? It should be real enough that customers won’t realize it’s just a prototype.
- When should I show others my prototype? Early and often. Don’t let yourself get too far down a single path before you start getting feedback from colleagues. Show your prototype to customers after you and your colleagues have ironed out the kinks.
- Who should I show it to? Start with the people in your design or product team. Be sure to get an engineer’s perspective to ensure the design you’re proposing is technically feasible.
- How should I present my prototype? It’s always best to show the prototype on the target device if possible. Frame the problem you’re trying to solve before you ask for feedback from others.
We’re fortunate to know the importance of testing, and to have access to tools that make capturing feedback cheap and easy. Whether remote or in person, your team can build fast feedback into your process so you can build better products faster.