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svelte/test/store/index.js

371 lines
6.8 KiB

import * as assert from 'assert';
import { readable, writable, derived, get } from '../../store';
describe('store', () => {
describe('writable', () => {
it('creates a writable store', () => {
const count = writable(0);
const values = [];
const unsubscribe = count.subscribe(value => {
values.push(value);
});
count.set(1);
count.update(n => n + 1);
unsubscribe();
count.set(3);
count.update(n => n + 1);
assert.deepEqual(values, [0, 1, 2]);
});
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(() => {
called += 1;
});
store.set(obj);
assert.equal(called, 2);
store.update(obj => obj);
assert.equal(called, 3);
});
it('only calls subscriber once initially, including on resubscriptions', () => {
let num = 0;
const store = writable(num, set => set(num += 1));
let count1 = 0;
let count2 = 0;
store.subscribe(() => count1 += 1)();
assert.equal(count1, 1);
const unsubscribe = store.subscribe(() => count2 += 1);
assert.equal(count2, 1);
unsubscribe();
});
});
describe('readable', () => {
it('creates a readable store', () => {
let running;
let tick;
const store = readable(undefined, set => {
tick = set;
running = true;
set(0);
return () => {
tick = () => { };
running = false;
};
});
assert.ok(!running);
const values = [];
const unsubscribe = store.subscribe(value => {
values.push(value);
});
assert.ok(running);
tick(1);
tick(2);
unsubscribe();
assert.ok(!running);
tick(3);
tick(4);
assert.deepEqual(values, [0, 1, 2]);
});
});
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();
});
it('prevents diamond dependency problem', () => {
const count = writable(0);
const values = [];
const a = derived(count, $count => {
return 'a' + $count;
});
const b = derived(count, $count => {
return 'b' + $count;
});
const combined = derived([a, b], ([a, b]) => {
return a + b;
});
const unsubscribe = combined.subscribe(v => {
values.push(v);
});
assert.deepEqual(values, ['a0b0']);
count.set(1);
assert.deepEqual(values, ['a0b0', 'a1b1']);
unsubscribe();
});
it('derived dependency does not update and shared ancestor updates', () => {
const root = writable({ a: 0, b:0 });
const values = [];
const a = derived(root, $root => {
return 'a' + $root.a;
});
const b = derived([a, root], ([$a, $root]) => {
return 'b' + $root.b + $a;
});
const unsubscribe = b.subscribe(v => {
values.push(v);
});
assert.deepEqual(values, ['b0a0']);
root.set({ a: 0, b: 1 });
assert.deepEqual(values, ['b0a0', 'b1a0']);
unsubscribe();
});
it('is updated with safe_not_equal logic', () => {
const arr = [0];
const number = writable(1);
const numbers = derived(number, $number => {
arr[0] = $number;
return arr;
});
const concatenated = [];
const unsubscribe = numbers.subscribe(value => {
concatenated.push(...value);
});
number.set(2);
number.set(3);
assert.deepEqual(concatenated, [1, 2, 3]);
unsubscribe();
});
it('calls a cleanup function', () => {
const num = writable(1);
const values = [];
const cleaned_up = [];
const d = derived(num, ($num, set) => {
set($num * 2);
return function cleanup() {
cleaned_up.push($num);
};
});
num.set(2);
const unsubscribe = d.subscribe(value => {
values.push(value);
});
num.set(3);
num.set(4);
assert.deepEqual(values, [4, 6, 8]);
assert.deepEqual(cleaned_up, [2, 3]);
unsubscribe();
assert.deepEqual(cleaned_up, [2, 3, 4]);
});
it('discards non-function return values', () => {
const num = writable(1);
const values = [];
const d = derived(num, ($num, set) => {
set($num * 2);
return {};
});
num.set(2);
const unsubscribe = d.subscribe(value => {
values.push(value);
});
num.set(3);
num.set(4);
assert.deepEqual(values, [4, 6, 8]);
unsubscribe();
});
it('allows derived with different types', () => {
const a = writable('one');
const b = writable(1);
const c = derived([a, b], ([a, b]) => `${a} ${b}`);
assert.deepEqual(get(c), 'one 1');
a.set('two');
b.set(2);
assert.deepEqual(get(c), 'two 2');
});
});
describe('get', () => {
it('gets the current value of a store', () => {
const store = readable(42, () => { });
assert.equal(get(store), 42);
});
it('works with RxJS-style observables', () => {
const observable = {
subscribe(fn) {
fn(42);
return {
unsubscribe: () => {}
};
}
};
assert.equal(get(observable), 42);
});
});
});