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kenichi-shibata/counter-test.html

Created November 26, 2015 04:42
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using deep freeze to test if the states are mutating
Raw
counter-test.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Avoiding mutations</title>
<script src="https://wzrd.in/standalone/expect@latest"></script>
<script src="https://wzrd.in/standalone/deep-freeze@latest"></script>
</head>
<body>
</body>
</html>
Raw
counter-test.js
const addCounter = (list) => {
return [...list,0];
};
const removeCounter = (list, index) => {
return [
...list.slice(0, index),
...list.slice(index + 1)
];
};
const incrementCounter = (list, index) => {
// return list
// .slice(0,index)
// .concat(list[index]+1)
// .concat(list.slice(index+1));
return[
...list.slice(0,index),
list[index]+1,
...list.slice(index+1)
] ;
};
const testAddCounter = () => {
const listBefore = [];
const listAfter = [0];
deepFreeze(listBefore);
expect(
addCounter(listBefore)
).toEqual(listAfter);
};
const testRemoveCounter = () => {
const listBefore = [0, 10, 20];
const listAfter = [0, 20];
deepFreeze(listBefore);
expect(
removeCounter(listBefore, 1)
).toEqual(listAfter);
};
const testIncrementCounter = () => {
const listBefore = [0, 10, 20];
const listAfter = [0, 11, 20];
deepFreeze(listBefore);
expect(
incrementCounter(listBefore, 1)
).toEqual(listAfter);
};
testAddCounter();
testRemoveCounter();
testIncrementCounter();
console.log('All tests passed');
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