ExampleValidator.js

// services/validators/ExampleValidator.js
export class ExampleValidator {
    validateFoo(input) {
        return input.length === 5;
    }
}

ExampleValidator.test.js

//test/services/validators/ExampleValidator.test.js
import {ExampleValidator} from '@/services/validators/ExampleValidator';

describe('ExampleValidator', function () {
    let validator;

    beforeEach(function () {
        validator = new ExampleValidator();
    });

    const testCases = [
      [5, false],
      [undefined, false],
      [null, false],
      ['', false],
      ['5', false],
      [12345, false],
      ['12345', true],
    ];

    testCases.forEach((testCase) => {
        const [input, expected] = testCase;
        test('validateFoo', () => {
            const result = validator.validateFoo(input);

            expect(result).toBe(expected);
        });
    });
});