10 Matching Annotations
  1. Last 7 days
    1. Storybook integrates with Jest Snapshot through an add-on called StoryShots. StoryShots adds automatic Jest Snapshot Testing to our codebase by using our existing Storybook stories as the input for Jest Snapshot Testing.
  2. Nov 2019
    1. If you're writing a tool for developers, it's a really common case that you want to write a test to ensure that a good error or warning message is logged to the console for the developers using your tool. Before snapshot testing I would always write a silly regex that got the basic gist of what the message should say, but with snapshot testing it's so much easier.
    2. (After all, it's not like the past snapshot was well understood or carefully expressed authorial intent.) As a result, if a snapshot test fails because some intended behavior disappeared, then there's little stated intention describing it and we'd much rather regenerate the file than spend a lot of time agonizing over how to get the same test green again.
    3. They are generated files, and developers tend to be undisciplined about scrutinizing generated files before committing them, if not at first then definitely over time. Most developers, upon seeing a snapshot test fail, will sooner just nuke the snapshot and record a fresh passing one instead of agonizing over what broke it.
    4. Good tests encode the developer's intention, they don't only lock in the test's behavior without editorialization of what's important and why. Snapshot tests lack (or at least, fail to encourage) expressing the author's intent as to what the code does (much less why)
    1. I very rarely use snapshot testing with react and I certainly wouldn't use it with shallow. That's a recipe for implementation details. The whole snapshot is nothing but implementation details (it's full of component and prop names that change all the time on refactors). It'll fail any time you touch the component and the git diff for the snapshot will look almost identical to the one for your changes to the component.This will make people careless about to the snapshot updates because they change all the time. So it's basically worthless (almost worse than no tests because it makes you think you're covered when you're not and you won't write proper tests because they're in place).
    1. Snapshot testing is great as it let us capture strings that represent our rendered components and the store it in a separate snapshot file to compare later in order to ensure that UI is not change. While it is ideal for React apps, we can use snapshots for comparing values that are serialized from other frameworks.
    2. Snapshot Test: Introduced by Facebook’s library Jest, Snapshot Tests should be the lightweight variation of testing (React) components. It should be possible to create a DOM snapshot of a component once a test for it runs for the first time and compare this snapshot to a future snapshot, when the test runs again, to make sure that nothing has changed. If something has changed, the developer has to either accept the new snapshot test (the developer is okay with the changes) or deny them and fix the component instead.