Using NodeJs Unit Testing(Jest)

  • Why Unit Testing
    • project starts simple, but grows more and more complex
    • horrifying functions start a simple way
    • You must think longer than your nose goes(Swedish sayings proverb)
  • add shipping
    • if the total amount is greater than 1000, then it’s free
    • instead of thinking lots of cases at the same time, we break it down by several isolated steps
  • add taxes
  • Happy Test
    • the main function the most time program spend

TDD 3 ways

- obvious implementation
- fake it until you make it
- triangalation

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function orderFilterTotal(order) {
    // 直接返回結果不需要再用一個變數來接
    // 三元表達式(item.quantity ? item.quantity : 1)
    return order.items
    .reduce((total, item) => {return (item.price * (item.quantity || 1) + total) }, 0);
}


if(orderFilterTotal({
    items: [
        {name:'cat food', price: 8, quantity: 2},
        {name:'cat cage', price: 800, quantity: 3}
    ]
}) != 2416) {
    throw new Error("Check Fail: Quantity Error)")
}

if(orderFilterTotal({
    items: [
        {name:'cat food', price: 3}
    ]
}) != 3) {
    throw new Error("Check Fail: No Quantity")
}



if(orderFilterTotal({
    items: [
        {name:'cat food', price: 8},
        {name:'cat cage', price: 800}
    ]
}) != 808) {
    throw new Error("Check Fail: Happy Test(Example 1)")
}

if(orderFilterTotal({
    items: [
        {name:'cat toy', price: 30},
        {name:'cat towel', price: 40}
    ]
}) != 70) {
    throw new Error("Check Fail: Happy Test(Example 2)")
}

Jest Auto Test

  • You need to notice your test file name to be xxxx.test.js format
    • it doesn’t matter the test file goes, but the file name matter
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// Happy Path
it('works', () => {
    expect(1).toBe(1);
})