Test cases para el ejercicio de Calculadora del curso de RN de Fernando Herrera

CalculadoraScreen.test.tsx

import * as React from 'react';
import { CalculadoraScreen } from "../CalculadoraScreen";
import {render, fireEvent} from '@testing-library/react-native' 

describe('<CalculadoraScreen />', () => {

    describe('results', () => {

        it('inits main result with zero', () => {
            const {assertResult} = renderCalculadora()
            assertResult('0')
        })

        it('hides previous result by default', () => {
            const {assertPreviousDoesNotExist} = renderCalculadora()
            assertPreviousDoesNotExist()
        })
        
        it('updates both results when + is pressed', () => {
            const {press, assertResult, assertPreviousResult} = renderCalculadora()
            press('1')
            press('+')
            assertPreviousResult('1')
            assertResult('0')
        })
        
        it('updates both results when - is pressed', () => {
            const {press, assertResult, assertPreviousResult} = renderCalculadora()
            press('1')
            press('-')
            assertPreviousResult('1')
            assertResult('0')
        })
        
        it('updates both results when X is pressed', () => {
            const {press, assertResult, assertPreviousResult} = renderCalculadora()
            press('1')
            press('X')
            assertPreviousResult('1')
            assertResult('0')
        })
        
        it('updates both results when / is pressed', () => {
            const {press, assertResult, assertPreviousResult} = renderCalculadora()
            press('1')
            press('/')
            assertPreviousResult('1')
            assertResult('0')
        })
    })

    describe('number interaction', () => {

        it('concatenates multiple numbers', () => {
            const {press, assertResult} = renderCalculadora();
            press('1')
            press('2')
            press('3')
            assertResult('123')
        })

        describe('starts with zero', () => {

            it('replaces zero with a number', () => {
                const {press, assertResult} = renderCalculadora();
                press('1')
                assertResult('1')
            })

            it('ignores multiple zeros if there is no dot', () => {
                const {press, assertResult} = renderCalculadora();
                press('0')
                press('0')
                press('0')
                press('0')
                assertResult('0')
            })

            it('only allows a single dot', () => {
                const {press, assertResult} = renderCalculadora()
                press('.')
                press('.')
                press('.')
                assertResult('0.')
            })

            it('adds multiple zeros if there is a dot', () => {
                const {press, assertResult} = renderCalculadora()
                press('.')
                press('0')
                press('0')
                press('0')
                press('0')
                press('0')
                assertResult('0.00000')
            })

            it('supports decimals', () => {
                const {press, assertResult} = renderCalculadora()
                press('.')
                press('1')
                assertResult('0.1')
            })

            it('avoids 0000.0, should be 0.0', () => {
                const {press, assertResult} = renderCalculadora()
                press('0')
                press('0')
                press('0')
                press('0')
                press('.')
                press('0')
                assertResult('0.0')
            })

            it('keeps negative sign for first digit', () => {
                const {press, assertResult} = renderCalculadora()
                press('+/-')
                press('1')
                assertResult('-1')
            })
        })

    });

    describe('positive negative switch', () => {
        it('toogles between positive and negative', () => {
            const {press, assertResult} = renderCalculadora()
            press('+/-')
            assertResult('-0')
            press('+/-')
            assertResult('0')
        })
    })

    describe('clear', () => {
        it('resets to zero', () => {
            const {press, assertResult} = renderCalculadora()
            press('C')
            assertResult('0')
        })
        it('resets to zero regardless of number of digits', () => {
            const {press, assertResult} = renderCalculadora()
            press('1')
            press('1')
            press('1')
            press('C')
            assertResult('0')
        })
        it('hides previous number when clear is triggered', () => {
            const {press, assertPreviousDoesNotExist} = renderCalculadora()
            press('1')
            press('+')
            press('C')
            assertPreviousDoesNotExist() // because it's back to zero
        })
    })

    describe('plus', () => {
        it('sums single digit numbers', () =>{
            const {press, assertResult} = renderCalculadora()
            press('1')
            press('+')
            press('2')
            press('=')
            assertResult('3')
        })
        it('sums positive and negative numbers', () =>{
            const {press, assertResult} = renderCalculadora()
            press('+/-')
            press('1')
            press('+')
            press('1')
            press('=')
            assertResult('0')
        })
    })

    describe('minus', () => {
        it('substracts single digit numbers', () =>{
            const {press, assertResult} = renderCalculadora()
            press('5')
            press('-')
            press('3')
            press('=')
            assertResult('2')
        })
        it('substracts below zero', () =>{
            const {press, assertResult} = renderCalculadora()
            press('1')
            press('-')
            press('5')
            press('=')
            assertResult('-4')
        })
        it('substracts negative and positive numbers', () =>{
            const {press, assertResult} = renderCalculadora()
            press('+/-')
            press('1')
            press('-')
            press('5')
            press('=')
            assertResult('-6')
        })
    })

    describe('multiply', () => {
        it('multiples two positive numbers', () => {
            const {press, assertResult} = renderCalculadora()
            press('2')
            press('X')
            press('3')
            press('=')
            assertResult('6')
        })
        it('multiples two negative numbers', () => {
            const {press, assertResult} = renderCalculadora()
            press('+/-')
            press('2')
            press('X')
            press('3')
            press('+/-')
            press('=')
            assertResult('6')
        })
        it('multiples a positive and a negative number', () => {
            const {press, assertResult} = renderCalculadora()
            press('+/-')
            press('2')
            press('X')
            press('3')
            press('=')
            assertResult('-6')
        })
    })

    describe('divide', () => {
        it('divides divisible numbers', () => {
            const {press, assertResult} = renderCalculadora()
            press('6')
            press('/')
            press('2')
            press('=')
            assertResult('3')
        })
        it('divides non divisible numbers', () => {
            const {press, assertResult} = renderCalculadora()
            press('5')
            press('/')
            press('2')
            press('=')
            assertResult('2.5')
        })
        it('divides a positive and a negative number', () => {
            const {press, assertResult} = renderCalculadora()
            press('6')
            press('/')
            press('+/-')
            press('2')
            press('=')
            assertResult('-3')
        })
        it('divides with periodic decimals', () => {
            const {press, assertResult} = renderCalculadora()
            press('1')
            press('/')
            press('3')
            press('=')
            assertResult('0.3333333333333333')
        })
    })

    describe('delete', () => {
        it('does nothing when the result is already zero', () => {
            const {press, assertResult} = renderCalculadora()
            press('del')
            press('del')
            press('del')
            assertResult('0')
        })
        it('deletes last digit of positive number', () => {
            const {press, assertResult} = renderCalculadora()
            press('1')
            press('2')
            press('3')
            press('del')
            assertResult('12')
        })
        it('resets to zero when the result is negative single digit', () => {
            const {press, assertResult} = renderCalculadora()
            press('+/-')
            press('1')
            press('del')
            assertResult('0')
        })
        it('resets to zero when the result is zero + dot', () => {
            const {press, assertResult} = renderCalculadora()
            press('.')
            press('del')
            assertResult('0')
        })
    });

});

type AllowedDigits = '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' | '0' | '.'

type AllowedOperations = '+' | '-' | 'X' | '/' | '=' | 'del' | 'C' | '+/-' 

interface TestActions {
    press: (value: AllowedDigits | AllowedOperations) => void
    assertResult: (expected: string) => void
    assertPreviousResult: (expected: string) => void
    assertPreviousDoesNotExist: () => void
}

const renderCalculadora = () : TestActions => { 
    const wrapper = render(<CalculadoraScreen/>)
    return {
        press: (number: AllowedDigits | AllowedOperations) => {
            fireEvent.press(wrapper.getByTestId(number))
        },
        assertResult: (expected: string) => {
            expect(wrapper.getByTestId('resultado').props.children).toBe(expected)
        },
        assertPreviousResult: (expected: string) => {
            expect(wrapper.getByTestId('resultado-anterior').props.children).toBe(expected)
        },
        assertPreviousDoesNotExist: () => {
            expect(wrapper.queryByTestId('resultado-anterior')).toBeNull()
        }
    }
}