I Loved Snapshots in 2016. A Decade Later, Let’s Revisit

A presentation at PragueJS in October 2025 in Prague, Czechia by Robin Pokorny

Slide 1

2025, 30Oct = 24Dec I LOVED SNAPSHOTS IN 2016 A Decade Later, Let’s Revisit ROBIN POKORNY

Slide 2

Slide 3

Slide 4

Slide 5

TONIGHT 01 02 03 WHAT IS SNAPSHOT TESTING WHAT WENT WRONG WHAT NOW?

Slide 6

01 WHAT IS SNAPSHOT TESTING

Slide 7

Slide 8

Slide 9

Slide 10

Slide 11

Slide 12

Slide 13

Slide 14

02 WHAT WENT WRONG

Slide 15

Slide 16

Slide 17

‘The most common drawback is the fragility of snapshot tests’ —STIP PAPER

Slide 18

LACK OF DEVELOPER INTENTION Tests don’t encode what’s important GENERATED FILE PROBLEM Need manual verification LARGE SNAPSHOTS Developers don’t scrutinize them HIGH FALSE NEGATIVES Tests fail when code is actually fine

Slide 19

Slide 20

03 WHAT NOW?

Slide 21

Slide 22

USE ● ● ● ● ● API response structures (not UI) Error messages and CLI output for developer-facing tools Code transformations Small, stable components in design systems Legacy refactoring AVOID ● ● ● ● ● Large component trees Components with frequent changes “It renders” smoke tests (use linting instead) Testing behavior As primary testing strategy

Slide 23

Slide 24

https://selfie.dev

Slide 25

TAKEAWAY SNAPSHOTS PROVIDE VALUE WHEN USED EFFECTIVELY

Slide 26

WEB me@robinpokorny.com NAME IN/IG/YT Let’s connect

Slide 27

STATE OF JS https://survey.devographics.com/survey/state-of-js/2025

Slide 28