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svelte/test/store/index.js

200 lines
3.6 KiB

import * as assert from 'assert';
import { readable, writable, derived, get } from '../../store.js';
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describe('store', () => {
describe('writable', () => {
it('creates a writable store', () => {
const count = writable(0);
const values = [];
const unsubscribe = count.subscribe(value => {
values.push(value);
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});
count.set(1);
count.update(n => n + 1);
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unsubscribe();
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count.set(3);
count.update(n => n + 1);
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assert.deepEqual(values, [0, 1, 2]);
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});
it('calls provided subscribe handler', () => {
let called = 0;
const store = writable(0, () => {
called += 1;
return () => called -= 1;
});
const unsubscribe1 = store.subscribe(() => {});
assert.equal(called, 1);
const unsubscribe2 = store.subscribe(() => {});
assert.equal(called, 1);
unsubscribe1();
assert.equal(called, 1);
unsubscribe2();
assert.equal(called, 0);
});
it('does not assume immutable data', () => {
const obj = {};
let called = 0;
const store = writable(obj);
store.subscribe(value => {
called += 1;
});
store.set(obj);
assert.equal(called, 2);
store.update(obj => obj);
assert.equal(called, 3);
});
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});
describe('readable', () => {
it('creates a readable store', () => {
let running;
let tick;
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const store = readable(undefined, set => {
tick = set;
running = true;
set(0);
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return () => {
tick = () => {};
running = false;
};
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});
assert.ok(!running);
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const values = [];
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const unsubscribe = store.subscribe(value => {
values.push(value);
});
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assert.ok(running);
tick(1);
tick(2);
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unsubscribe();
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assert.ok(!running);
tick(3);
tick(4);
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assert.deepEqual(values, [0, 1, 2]);
});
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});
describe('derived', () => {
it('maps a single store', () => {
const a = writable(1);
const b = derived(a, n => n * 2);
const values = [];
const unsubscribe = b.subscribe(value => {
values.push(value);
});
a.set(2);
assert.deepEqual(values, [2, 4]);
unsubscribe();
a.set(3);
assert.deepEqual(values, [2, 4]);
});
it('maps multiple stores', () => {
const a = writable(2);
const b = writable(3);
const c = derived(([a, b]), ([a, b]) => a * b);
const values = [];
const unsubscribe = c.subscribe(value => {
values.push(value);
});
a.set(4);
b.set(5);
assert.deepEqual(values, [6, 12, 20]);
unsubscribe();
a.set(6);
assert.deepEqual(values, [6, 12, 20]);
});
it('passes optional set function', () => {
const number = writable(1);
const evens = derived(number, (n, set) => {
if (n % 2 === 0) set(n);
}, 0);
const values = [];
const unsubscribe = evens.subscribe(value => {
values.push(value);
});
number.set(2);
number.set(3);
number.set(4);
number.set(5);
assert.deepEqual(values, [0, 2, 4]);
unsubscribe();
number.set(6);
number.set(7);
number.set(8);
assert.deepEqual(values, [0, 2, 4]);
});
it('prevents glitches', () => {
const lastname = writable('Jekyll');
const firstname = derived(lastname, n => n === 'Jekyll' ? 'Henry' : 'Edward');
const fullname = derived([firstname, lastname], names => names.join(' '));
const values = [];
const unsubscribe = fullname.subscribe(value => {
values.push(value);
});
lastname.set('Hyde');
assert.deepEqual(values, [
'Henry Jekyll',
'Edward Hyde'
]);
unsubscribe();
});
});
describe('get', () => {
it('gets the current value of a store', () => {
const store = readable(42, () => {});
assert.equal(get(store), 42);
});
});
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});