docs(ES6ClassMocks): add clarity for module factory limitations #12453
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- close jestjs#11862 - related to jestjs#11455
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Should I also update |
no this is good, thanks |
SimenB
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Feb 22, 2022
docs/Es6ClassMocks.md
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| @@ -140,7 +140,11 @@ jest.mock('./sound-player', () => { | |||
| }); | |||
| ``` | |||
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| A limitation with the factory parameter is that, since calls to `jest.mock()` are hoisted to the top of the file, it's not possible to first define a variable and then use it in the factory. An exception is made for variables that start with the word 'mock'. It's up to you to guarantee that they will be initialized on time! For example, the following will throw an out-of-scope error due to the use of 'fake' instead of 'mock' in the variable declaration: | |||
| :::caution | |||
| Since calls to `jest.mock()` are hoisted to the top of the file, Jest prevents access to out-of-scope variables. By default, you cannot first define a variable and then use it in the factory. Jest will disable this check for variables that start with the word 'mock'. However, it is still up to you to guarantee that they will be initialized on time. Be aware of [Temporal Dead Zone](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let#temporal_dead_zone_tdz). | |||
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temporal dead zone, I didn't know this had a name! 😀 Awesome stuff
SimenB
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This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs. |
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ReferenceError: Cannot access 'myMock' before initializationif test itself and 'myMock' are in different files #11455Summary
Modify verbiage and include another code example to make it clear that there is a language-level limitation outside of Jest when using the module factory pattern.