Jest testing a loop with Booleans

May 26, 2022

I have the following function in Jest. I have a method called isAquatic that returns a bool depending on the animal.

        const nonAquaticAnimal = ["tiger", "cat", "lion"]
        test.each(nonAquaticAnimal)(
          '.isAquatic',
          (input, false) => {
            const animal = isAquatic(input)
            expect(animal).toBe(false);
          },
        );

I have an error that says identifier false is a reserved word and cannot be used here. How can I loop through the array and call this method which returns a boolean?

>Solution :

The array argument passed to test.each is usually a 2D array, so you can have the animal and the expected result for that animal in the nonAquaticAnimals array. And the test function would both the items in as function arguments.

You can have your test as follows:

const nonAquaticAnimals = [
  ["tiger", false],
  ["cat", false],
  ["lion", false],
];
test.each(nonAquaticAnimals)(".isAquatic", (animal, expected) => {
  expect(isAquatic(animal)).toBe(expected);
});

You can also omit the expected value from your array if you find it redundant:

const nonAquaticAnimals = ["tiger", "cat", "lion"];
test.each(nonAquaticAnimals)(".isAquatic", (animal) => {
  expect(isAquatic(animal)).toBe(false);
});