Jest test from docs fails on simple Managed app

Expo SDK
1

Hi,

I’ve created a new Managed Expo project following the Up and Running guide and the app runs, but when I follow the instructions for Testing with Jest the test fails.

I’m new to Expo; I came across the project because a friend is using it in his app and I would like to help him out. I decided to get started by writing tests for the existing code, but ran into issues (more on that another time), so I decided to start a project from scratch and make sure that I understood how to test a Managed Expo project.

I created a new project by following the Up and Running guide and selected the tabs project as suggested. The development server starts correctly and I am able to see the app on my phone using the Android Expo app.

I didn’t make any modifications to the code, I just headed to the section on Testing with Jest and followed those steps. I created the App.test.js unit test and then ran Jest via yarn test.

However, the test failed with the following:

Cannot log after tests are done. Did you forget to wait for something async in your test?
    Attempted to log "TypeError: FileSystem.getInfoAsync is not a function
        at Asset._downloadAsyncManagedEnv$ (/Users/foo/Code/a-test-expo-app/node_modules/expo-asset/src/Asset.ts:170:30)
        at tryCatch (/Users/foo/Code/a-test-expo-app/node_modules/@babel/runtime/node_modules/regenerator-runtime/runtime.js:45:40)
        at Generator.invoke [as _invoke] (/Users/foo/Code/a-test-expo-app/node_modules/@babel/runtime/node_modules/regenerator-runtime/runtime.js:271:22)
        at Generator.prototype.(anonymous function) [as next] (/Users/foo/Code/a-test-expo-app/node_modules/@babel/runtime/node_modules/regenerator-runtime/runtime.js:97:21)
        at tryCatch (/Users/foo/Code/a-test-expo-app/node_modules/@babel/runtime/node_modules/regenerator-runtime/runtime.js:45:40)
        at invoke (/Users/foo/Code/a-test-expo-app/node_modules/@babel/runtime/node_modules/regenerator-runtime/runtime.js:135:20)
        at /Users/foo/Code/a-test-expo-app/node_modules/@babel/runtime/node_modules/regenerator-runtime/runtime.js:170:11
        at tryCallTwo (/Users/foo/Code/a-test-expo-app/node_modules/promise/lib/core.js:45:5)
        at doResolve (/Users/foo/Code/a-test-expo-app/node_modules/promise/lib/core.js:200:13)
        at new Promise (/Users/foo/Code/a-test-expo-app/node_modules/promise/lib/core.js:66:3)".
...

 FAIL  ./App.test.js
  ● <App /> › has 1 child

    TypeError: Cannot read property 'children' of null

       7 |   it('has 1 child', () => {
       8 |     const tree = renderer.create(<App />).toJSON();
    >  9 |     expect(tree.children.length).toBe(1);
         |                 ^
      10 |   });
      11 | });

      at Object.children (App.test.js:9:17) FAIL  ./App.test.js
  ● <App /> › has 1 child

    TypeError: Cannot read property 'children' of null

       7 |   it('has 1 child', () => {
       8 |     const tree = renderer.create(<App />).toJSON();
    >  9 |     expect(tree.children.length).toBe(1);
         |                 ^
      10 |   });
      11 | });

      at Object.children (App.test.js:9:17)

I can see in node_modules that under the expo-file-system directory that the TypeScript file exists and the function is defined:

export declare function getInfoAsync(fileUri: string, options?: {
    md5?: boolean;
    cache?: boolean;
}): Promise<FileInfo>;

Does anyone know why Jest isn’t picking up this definition and how to get a simple test to work with a scaffolded project?

Thanks

2

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