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atom_test.js
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atom_test.js
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'use strict';
const derivable = require('../dist/derivable');
describe("the humble atom", () => {
let n;
beforeEach(() => {
n = derivable.atom(0);
});
it("can be dereferenced via .get to obtain its current state", () => {
expect(n.get()).toBe(0);
});
it("can be .set to change its current state", () => {
n.set(1);
expect(n.get()).toBe(1);
});
it("can .update (a la swap in clojure)", () => {
n.set(1);
const double = x => x * 2;
n.update(double);
expect(n.get()).toBe(2);
n.update(double);
expect(n.get()).toBe(4);
});
it('can take on temporary values inside a transaction', () => {
const a = derivable.atom("a");
derivable.transact(abort1 => {
a.set("b");
expect(a.get()).toBe("b");
derivable.transact(abort2 => {
a.set("c");
expect(a.get()).toBe("c");
abort2();
});
expect(a.get()).toBe("b");
abort1();
});
expect(a.get()).toBe("a");
});
it('should be able to go back to its original value with no ill effects', () => {
const a = derivable.atom("a");
let reacted = false;
a.react(() => {
reacted = true;
}, { skipFirst: true });
// no reaction to begin with
expect(reacted).toBe(false);
derivable.transact(() => {
a.set("b");
a.set("a");
});
// no reaction should take place
expect(reacted).toBe(false);
});
it('can keep transaction values if they are\'t aborted', () => {
const a = derivable.atom("a");
derivable.transact(() => {
a.set("b");
derivable.transact(() => {
a.set("c");
});
expect(a.get()).toBe("c");
});
expect(a.get()).toBe("c");
});
it('can include an equality-checking function', () => {
const a = derivable.atom(0);
const b = a.withEquality(() => false);
// creates a brand new atom
expect(a).not.toBe(b);
let numReactions = 0;
a.react(() => {
numReactions++;
}, { skipFirst: true });
b.react(() => {
numReactions++;
}, { skipFirst: true });
expect(numReactions).toBe(0);
a.set(0);
expect(numReactions).toBe(0);
a.set(0);
expect(numReactions).toBe(0);
b.set(0);
expect(numReactions).toBe(1);
b.set(0);
expect(numReactions).toBe(2);
});
it('only likes functions or falsey things for equality functions', () => {
derivable.atom(4).withEquality('');
expect(() => {
derivable.atom(4).withEquality('yo');
}).toThrow();
derivable.atom(4).withEquality(0);
expect(() => {
derivable.atom(4).withEquality(7);
}).toThrow();
derivable.atom(4).withEquality(null);
derivable.atom(4).withEquality(void 0);
});
});
describe('the concurrent modification of _reactors bug', () => {
it('doesnt happen any more', () => {
const $A = derivable.atom(false);
const $B = derivable.atom(false);
let A_success = false;
let C_success = false;
$A.react(() => {
A_success = true;
}, { from: $A });
const $C = $A.and($B);
$C.react(() => {
C_success = true;
}, { from: $C });
expect(A_success).toBe(false);
expect(C_success).toBe(false);
// used to be that this would cause the 'from' controller on C to be ignored
// during the ._maybeReact iteration in .set
$A.set(true);
expect(A_success).toBe(true);
expect(C_success).toBe(false);
$B.set(true);
expect(C_success).toBe(true);
});
});