I want to remember the technical explanation of this behavior and how to do it properly
sample.js (in reality this is a really long mock which is why its in a separate file)
const data = {
a = 1,
nested: {
object: 'old'
}
}
export default data;
data.spec.js
import sampleData from './sample'
describe('sample', () => {
let data;
beforeEach(
data = sampleData
)
it('change data', () => {
data.nested.object = 'new'; // lets say value was old before
....
})
it('change data', () => {
console.log(data.nested.object) // i would think it would be 'old' but is still 'new'
....
})
My brain says that its doing so because all i did was add a pointer to the object and i'm still modifying the object so the beforeEach doesn't do anything. I feel like there's a longer explanation that I'm forgetting
But I want to know the proper way to do it. if I turn the sample data file to a function and have it 'return' the object each time That seems right given I use an arrow function. But that feels incorrect. Is there something I'm forgetting?
Your assumption is correct, just don't forget to make a copy of your test data before changing it.
For example:
beforeEach(() => {
data = structuredClone(sampleData);
});
Or for older ecmascript version:
beforeEach(() => {
data = { ...sampleData, nested: { ...sampleData.nested } };
});