Migration guide from @testing-library/react-native is missing some breaking changes

[TAGraves]

Hey all,

Stoked to see the two react-native testing libraries have finally merged! At Root, we have a fair number of testing library tests in our react native project. I tried upgrading @testing-library/react-native from v6 to v7 and about 20% of our tests are failing after following the upgrade guide.

Another engineer will be taking a closer look at the upgrade (I was just trying to get an idea of the effort involved), but looking through the errors I see at least the following undocumented breaking changes:

getByLabelText(...).getProp is not a function (see https://www.native-testing-library.com/docs/next/api-test-instance#getprop) -- this one is obviously replaced with .props instead

baseElement is undefined (see https://www.native-testing-library.com/docs/next/api-main#baseelement)

parentNode is undefined (see https://www.native-testing-library.com/docs/api-test-instance#parentnode) -- this one is really important for us as we use it a lot for testing styles in cases where we can guarantee what the "native" parent will be. From a quick check I'm not sure if there is a new equivalent (.parent behaves differently since there's no concept of a NativeTestInstance now)

string precision options are missing (see https://www.native-testing-library.com/docs/next/api-queries#precision)

If there are existing ways to migrate from these old patterns to the new ones, we'd love to hear it and see it added to the migration guide. If not -- we'd likely be happy to contribute to add some of this functionality back in!

[thymikee]

Hey! I think we can definitely add some of these back. I'm not so sure about parentNode because it smells like testing implementation details.

I'll be away from keyboard till next week, but I'm sure you can discuss it with @mdjastrzebski @Esemesek and @cross19xx and figure out the way forward 🙂

[TAGraves]

I'm not so sure about parentNode because it smells like testing implementation details.

Yes, I agree. I think we can probably get around it in our codebase by adding a matcher that recursively checks parents for the appropriate styles.

[manuelmhtr]

Also: asJSON does not exist. It need to be renamed to toJSON.

[artdent]

Also the getNodeText helper function, https://github.com/testing-library/native-testing-library/blob/master/src/lib/get-node-text.js, which could be replaced by a thin wrapper around the internal getChildrenAsText helper.

[thymikee]

Hey @TAGraves would you be so kind and create some action points / issues for us to implement? For example baseElement sounds like something that should be fairly easy to start with. Then we could add string precision API, because why not. The more compat with Testing Library, the better. I hope it's understandable that we started from a different place, but we have all the good intentions :)

I also noticed that you were a collaborator to the second library, so if you'd like to gain more privileges in this repo, please give me a shout at Discord (thymikee#1279) :)

[mdjastrzebski]

re parentNode: I've added "Ability to traverse host component tree easily (discussion)" #520.

[dephiros]

+1 for baseElement/Container. We use that at our company as a way to get at top level component which is useful in some cases where you don't have any specific text/content to query for

[dephiros]

Another behavior that I noticed while doing migration is:

• Before the query would return NativeTestInstance and it now return ReactTestInstance. This is already documented in the migration doc
• However, this does break existing tests in our codebase because our tests expect to query on the same element seeing in debug() which would have type View, Text... whereas ReactTestInstance's type the React component itself. This seems to go against the philosophy of not testing the implementation.
• The use case for us is to query the output style on a component

Appreciate direction if I am not using the new lib correctly

[mdjastrzebski]

@dephiros Please post sample test code of how are you using debug().

AFAIK debug is intended to output to console. Did you actually mean toJSON()?

[thymikee]

I think we could introduce something similar to NativeTestInstance, will need to think about it.

[dephiros]

Thank you for your response
@mdjastrzebski , I meant debug
This is a simplify example of the test that used to pass pre-v7. To get this test pass in the new version, we had to modify the test to check the prop of child(which is now an instance of ChildrenComponent instead of view. To me, checking style would follow closer to the not testing implementation details philosophy

const ChildComponent = ({color, text}) => {
  return <View style={{color}}></View>
}

const TestComponent = ({items}) => {
  return (
    <View testID='container'>
      {items.map((item) => (<ChildComponent key={item.color} {...item} />))}
    </View>
  );
}

fdescribe('Test', () => {
  const items = [
    {color: 'red'},
    {color: 'blue'},
    {color: 'yellow'},
  ];
  it('should output the right color', () => {
    const view = render(<TestComponent items={items} />);
    view.debug();
    const container = view.getByTestId('container');
    const children = container.children;
    children.forEach((child, index) => {
      expect(child).toHaveStyle(items[index]);
    });
  })
});

view.debug() (very similar to the previous version except the previous version has the extra wrapper)

    <View
      testID="container"
    >
      <View
        style={
          Object {
            "color": "red",
          }
        }
      />
      <View
        style={
          Object {
            "color": "blue",
          }
        }
      />
      <View
        style={
          Object {
            "color": "yellow",
          }
        }
      />
    </View>

[mikeduminy]

Here is an attempt to track all the functionality that IMO we should try to get in for v8

Missing functionality in v7 that was present in v6:

• string precision options (solved by feat(breaking): add text match options a.k.a string precision API #554)
• simple text matching (see Nested custom Text componentns not working correctly #515)
• support for custom queries (solved by Adding support for extending with custom queries #573)
• asJSON missing
• container missing (related feat: export container from render #567)
• baseElement missing (breaking change for those using snapshots)

Bugs in v7:

• waitFor can time out if you are using fake timers (solved by fix(breaking): use real timers internally to fix awaiting with fake timers #568)

Misc:

• add Guiding Principles to docs
• mocks for TouchableOpacity and TouchableHighlight (not present in react-native preset, affecting snapshots)

What we can probably ignore until we have further information:

• NativeTestInstance (parity with v6): eg. getProp, parentNode

[mdjastrzebski]

Closing as stale.

In case anyone involved considers any of the above mentioned points as a bug or missing feature, please fill a separate pull request for each item.