Expected [ ] to be [ ] Jasmine, how to check empty array

user_1904479 0
Viewed 48951

Getting error while trying to check for empty array. I tried using:

Case 1: By initializing as an array

expect(fixture.componentInstance.dataSource).toBe([]);

Case 2: By initializing as an array

let expectedAry = new Array;
expect(fixture.componentInstance.dataSource).toBe(expectedAry);

Both the case have the same error:

Expected [  ] to be [  ].

Arrays can also be checked by their length, the following works fine

expect(fixture.componentInstance.dataSource.length).toEqual(0);

0 length is an option, but not sure if that is the right way to check whether an array is empty. Do we have a better option for checking whether an array is empty?

jasmine angular unit-testing arrays javascript
3 Answers

toBe doesn't check the contents of the array, it only checks if the references are the same.

expect([1]).toBe([1]) will fail because the references are different.

You should use toEqual, which has some smarts to check the array contents as opposed to just doing a reference comparison.

user_1494360

Use toHaveSize matcher:

expect(array).toHaveSize(0);

It's strongly recommended to use because the error messages you get with it are much better (e.g. Error: Expected array to have size 0)

Coming with Jasmine 3.6: release docs

user_67749160

You can try like this -

expect(component.XYZ.length).toEqual(0);
user_116955840
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