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77 lines
1.5 KiB
Markdown
77 lines
1.5 KiB
Markdown
# Avoid using a callback in asynchronous tests (`no-test-callback`)
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Jest allows you to pass a callback to test definitions, typically called `done`,
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that is later invoked to indicate that the asynchronous test is complete.
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However, that means that if your test throws (e.g. because of a failing
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assertion), `done` will never be called unless you manually use `try-catch`.
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```js
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test('some test', done => {
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expect(false).toBe(true);
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done();
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});
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```
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The test above will time out instead of failing the assertions, since `done` is
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never called.
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Correct way of doing the same thing is to wrap it in `try-catch`.
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```js
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test('some test', done => {
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try {
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expect(false).toBe(true);
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done();
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} catch (e) {
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done(e);
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}
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});
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```
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However, Jest supports a second way of having asynchronous tests - using
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promises.
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```js
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test('some test', () => {
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return new Promise(done => {
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expect(false).toBe(true);
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done();
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});
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});
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```
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Even though `done` is never called here, the Promise will still reject, and Jest
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will report the assertion error correctly.
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## Rule details
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This rule triggers a warning if you have a `done` callback in your test.
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The following patterns are considered warnings:
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```js
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test('myFunction()', done => {
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// ...
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});
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test('myFunction()', function(done) {
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// ...
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});
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```
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The following patterns are not considered warnings:
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```js
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test('myFunction()', () => {
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expect(myFunction()).toBeTruthy();
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});
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test('myFunction()', () => {
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return new Promise(done => {
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expect(myFunction()).toBeTruthy();
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done();
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});
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});
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```
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