jest: Coverage flag breaks snapshot test

I think it’s because of code instrumentation

jest --coverage

    - Snapshot
    + Received
...
    -   onSelect={[Function onSelectHandler]}
    +   onSelect={[Function anonymous]}

Running with jest is just OK.

Source code and func name for onSelectHandler: jest:

    console.log src/components/pie-chart.js:44
      [Function: onSelectHandler]
    console.log src/components/pie-chart.js:45
      function onSelectHandler(_ref2){var nativeEvent=_ref2.nativeEvent;

      if(!onSelect){
      return;
      }
      onSelect(nativeEvent.index);
      }

And for jest --coverage:

    console.log src/components/pie-chart.js:44
      [Function]
    console.log src/components/pie-chart.js:45
      function (_ref2){var nativeEvent=_ref2.nativeEvent;++__cov_742n7agVtRgakP6RGrGnDGRBizg.f['3'];++__cov_742n7agVtRgakP6RGrGnDGRBizg.s['7'];

      if(!onSelect){++__cov_742n7agVtRgakP6RGrGnDGRBizg.b['1'][0];++__cov_742n7agVtRgakP6RGrGnDGRBizg.s['8'];
      return;
      }else{++__cov_742n7agVtRgakP6RGrGnDGRBizg.b['1'][1];}++__cov_742n7agVtRgakP6RGrGnDGRBizg.s['9'];
      onSelect(nativeEvent.index);
      }

How I can avoid this issue? Force use anonymous functions on every place? 😯

About this issue

Original URL
State: closed
Created 8 years ago
Comments: 22 (10 by maintainers)

Most upvoted comments

+1 @guigrpa screen shot 2016-11-23 at 7 21 02 pm That’s what I get after running jest --watch just after running jest --coverage (and having updated my snapshots with coverage)

vincentaudebert on Nov 23, 2016

In my case I’m using enzyme to snapshot a functional stateless component in React, and I get a failed snapshot assertion with coverage enabled, but it’s not Unknown - for me it renders Component:

-     <ListItem
+     <Component
          active={false}
          item={
            Object {
              "id": "thing",
              "name": "stuff",
            }
          }
          onClick={[Function]} />

I’d be happy to isolate a repro case for this setup if it helps at all. The curious part here is that all my other snapshots are fine, it’s just this instance of snapshotting a functional stateless component that has this differing output.

dotfold on Dec 11, 2016

@CGamesPlay you can use jest@^21.3.0-beta.2 and run yarn jest --clearCache. After this, jest should compile your code with the new istanbul instrument code for no problem (no --no-cache is needed).

tomchentw on Oct 24, 2017

For stateless components you need to define displayName prop of the Component. See this thread for more background: https://github.com/facebook/jest/issues/1824#issuecomment-250478026

thymikee on Dec 13, 2016

Hmmm… doesn’t solve the problem completely if for some reason you’re snapshotting a React element. It’s name will turn Unknown in the snapshot when you enable --coverage.

guigrpa on Nov 18, 2016

Will be fixed in 16.

cpojer on Sep 21, 2016

yeah this kind of sucks. Istanbul wraps functions with other anonymous functions and we take the function name that node gives to the rendered component 😦 ~ @cpojer

thymikee on Dec 13, 2016

@dotfold if you can isolate the test case, please file a new issue with it.

thymikee on Dec 11, 2016