Test if an array is empty or contains a certain object with

user_1098122 0
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I want to test if an array is empty or contains objects of a certain structure. In pseudo code it could be something like this:

expect([])
  .toHaveLength(0)
  .or
  .arrayContaining(
    expect.toMatchObject(
     { foo: expect.any(String) }
    )
  ) => true

expect([{foo: 'bar'}])
  .toHaveLength(0)
  .or
  .arrayContaining(
    expect.toMatchObject(
     { foo: expect.any(String) }
    )
  ) => true

expect([1])
  .toHaveLength(0)
  .or
  .arrayContaining(
    expect.toMatchObject(
      { foo: expect.any(String) }
    )
  ) => false

Maybe I'm getting it wrong on the how things work in Jest, but to me my problem looks like an or-question.

jestjs testing javascript
1 Answers

The best way to encapsulate a logical or in your test suite would be to just exclude the particular case inside of the test itself. For example:

it('has an array of objects', () => {
  if (arr.length > 0) {
    expect(arr).toBe(expect.arrayContaining(expect.toMatchObject({ foo: expect.any(String) })));
  }
});

However, I think a more unit test-friendly approach would be to separate your concerns. One test for when there is an empty array, and one test for when the foo property is set to 'bar', etc.

user_52135730
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