import { calcFactorial } from '../Factorial'
describe('calcFactorial', () => {
it('should return a statement for value "0"', () => {
expect(calcFactorial(0)).toBe('The factorial of 0 is 1.')
})
it('should return a statement for "null" and "undefined"', () => {
const nullFactorial = calcFactorial(null)
const undefinedFactorial = calcFactorial(undefined)
expect(nullFactorial).toBe(
'Sorry, factorial does not exist for null or undefined numbers.'
)
expect(undefinedFactorial).toBe(
'Sorry, factorial does not exist for null or undefined numbers.'
)
})
it('should not support negative numbers', () => {
const negativeFactorial = calcFactorial(-5)
expect(negativeFactorial).toBe(
'Sorry, factorial does not exist for negative numbers.'
)
})
it('should return the factorial of a positive number', () => {
const positiveFactorial = calcFactorial(3)
expect(positiveFactorial).toBe('The factorial of 3 is 6')
})
})