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May 24, 2017 10:19
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import {add} from "helpers" | |
const calculator = (a, b, op) => { | |
if (op == "+") | |
return add (a, b); | |
} | |
/******************************************************************** | |
When we unit test calculator, we are concerned with whether | |
calculator calls add helper or not if `op` is `+` and not with | |
whether calculator returns sum of `a` and `b` if op is `+` | |
When we test this with Jest, `add` from helpers is automatically | |
mocked to return undefined and we shouldn't be concerned about it. | |
And as it is auto mocked, we can easliy spy on it as below | |
*********************************************************************/ | |
describe("Calculator", () => { | |
it("should call 'add' helper, if op is '+'", () => { | |
// Given | |
let a = 10; | |
let b = 2; | |
let op = "+"; | |
// When | |
const result = calculator(a, b, op); | |
// Then | |
expect(add).toBeCalledWith(a, b); | |
}) | |
}); |
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