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doc: add guides on writing tests involving promises #20988
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@@ -223,6 +223,34 @@ countdown.dec(); | |
countdown.dec(); // The countdown callback will be invoked now. | ||
``` | ||
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#### Testing promises | ||
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When writing tests involving promises, either make sure that the | ||
`onFulfilled` or the `onRejected` handler is wrapped in | ||
`common.mustCall()` or `common.mustNotCall` accordingly, or | ||
call `common.crashOnUnhandledRejection()` in the top level of the | ||
test to make sure that unhandled rejections would result in a test | ||
failure. For example: | ||
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```javascript | ||
const common = require('../common'); | ||
const assert = require('assert'); | ||
const fs = require('fs').promises; | ||
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// Use `common.crashOnUnhandledRejection()` to make sure unhandled rejections | ||
// will fail the test | ||
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common.crashOnUnhandledRejection(); | ||
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// Or, wrap the `onRejected` handler in `common.mustNotCall()` | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Ditto, period) |
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fs.writeFile('test-file', 'test').catch(common.mustNotCall()); | ||
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// Or, wrap the `onFulfilled` handler in `common.mustCall()` | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Ditto, period) |
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fs.readFile('test-file').then( | ||
common.mustCall( | ||
(content) => assert.strictEqual(content.toString(), 'test') | ||
)); | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. It's an example, but I think it makes sense to add There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. @lpinca that is demonstrated in the first example...also the There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I'm not sure I understand, this const common = require('../common');
const assert = require('assert');
const fs = require('fs');
const fsPromises = fs.promises;
fs.writeFileSync('test-file', 'foo');
fsPromises.readFile('test-file').then(
common.mustCall((content) => {
assert.strictEqual(content.toString(), 'test');
})
); should make the test fails, but it doesn't if There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. @lpinca I see what you mean now, the |
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``` | ||
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Extra empty line. |
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### Flags | ||
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common.mustNotCall
->common.mustNotCall()
?