Examples of requiring React once instead of in every test?

[PsySecCorp]

This is what I have to do in order to get tests to work:

describe(function() {
  describe(function() {
    it(function() {
        var React = require('react');
        // Change the state of a compoennt
    })
    it(function() {
        var React = require('react');
        // Change the state of a compoennt
    })
  })
})

When I try to do this:

describe(function() {
  var React = require('react');
  describe(function() {
    it(function() {
        // Change the state of a compoennt
    })
    it(function() {
        // Change the state of a compoennt
    })
  })
})

I get error: TypeError: Cannot read property 'firstChild' of undefined

[awei01]

Not really a Jest issue. Check out jasmine docs: http://jasmine.github.io/

You should do this:

describe(function() {
    var React;
    beforeEach(function() {
        React = require('react');
    });
    it('should have access to React var', function() {
        expect(React).not.toBeUndefined();
    });
});

[simenbrekken]

Even if it's not a Jest issue it looks messy and leads to bugs. Why doesn't e.g Mocha have this issue?

[SegFaultx64]

This also makes the test runs very slow. Since HasteModuleLoader has to traverse the dependency tree for each test. I have a workaround for this but it breaks test "hygiene" by reusing mocks so I am hesitant to post it here.

[tchcxp]

Anyone looks into this issue?

[ghost]

Thank you for reporting this issue and appreciate your patience. We've notified the core team for an update on this issue. We're looking for a response within the next 30 days or the issue may be closed.

[cpojer]

The performance problems were fixed with #599.

To answer your question (and sorry I never saw this issue before :) ), jest gives you test isolation. It resets the module registry on every call to it to make sure you get a fresh environment. You can require React either on the top level (once) or inside of your beforeEach calls (for every test).

[github-actions]

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