You could do this, it was close to what you had already:
pm.test('Frequency Check', () => { _.each(pm.response.json(), (arrItem) => { pm.expect(arrItem.FREQUENCY).to.be.oneOf(["1 Month" , "3 Months" , "6 Months" , "1 Year rolling", "Since Inception"]) })})I changed the response data slightly, so you can see what it looks like when it fails:
