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feat(rules): no-try-expect (#331)
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# Prevent catch assertions in tests (no-try-expect) | ||
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This rule prevents the use of `expect` inside `catch` blocks. | ||
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## Rule Details | ||
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Expectations inside a `catch` block can be silently skipped. While Jest provides | ||
an `expect.assertions(number)` helper, it might be cumbersome to add this to | ||
every single test. Using `toThrow` concisely guarantees that an exception was | ||
thrown, and that its contents match expectations. | ||
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The following patterns are warnings: | ||
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```js | ||
it('foo', () => { | ||
try { | ||
foo(); // `foo` may be refactored to not throw exceptions, yet still appears to be tested here. | ||
} catch (err) { | ||
expect(err).toMatch(/foo error/); | ||
} | ||
}); | ||
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it('bar', async () => { | ||
try { | ||
await foo(); | ||
} catch (err) { | ||
expect(err).toMatch(/foo error/); | ||
} | ||
}); | ||
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it('baz', async () => { | ||
try { | ||
await foo(); | ||
} catch (err) { | ||
expect(err).toMatchObject({ code: 'MODULE_NOT_FOUND' }); | ||
} | ||
}); | ||
``` | ||
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The following patterns are not warnings: | ||
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```js | ||
it('foo', () => { | ||
expect(() => foo()).toThrow(/foo error/); | ||
}); | ||
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it('bar', async () => { | ||
await expect(fooPromise).rejects.toThrow(/foo error/); | ||
}); | ||
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it('baz', async () => { | ||
await expect(() => foo()).rejects.toThrow( | ||
expect.objectContaining({ code: 'MODULE_NOT_FOUND' }), | ||
); | ||
}); | ||
``` |
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import { RuleTester } from 'eslint'; | ||
import rule from '../no-try-expect'; | ||
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const ruleTester = new RuleTester({ | ||
parserOptions: { | ||
ecmaVersion: 2019, | ||
}, | ||
}); | ||
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ruleTester.run('no-try-catch', rule, { | ||
valid: [ | ||
`it('foo', () => { | ||
expect('foo').toEqual('foo'); | ||
})`, | ||
`it('foo', () => { | ||
expect('bar').toEqual('bar'); | ||
}); | ||
try { | ||
} catch { | ||
expect('foo').toEqual('foo'); | ||
}`, | ||
`it.skip('foo'); | ||
try { | ||
} catch { | ||
expect('foo').toEqual('foo'); | ||
}`, | ||
], | ||
invalid: [ | ||
{ | ||
code: `it('foo', () => { | ||
try { | ||
} catch (err) { | ||
expect(err).toMatch('Error'); | ||
} | ||
})`, | ||
errors: [ | ||
{ | ||
messageId: 'noTryExpect', | ||
}, | ||
], | ||
}, | ||
{ | ||
code: `it('foo', async () => { | ||
await wrapper('production', async () => { | ||
try { | ||
} catch (err) { | ||
expect(err).toMatch('Error'); | ||
} | ||
}) | ||
})`, | ||
errors: [ | ||
{ | ||
messageId: 'noTryExpect', | ||
}, | ||
], | ||
}, | ||
], | ||
}); |
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import { getDocsUrl, isTestCase } from './util'; | ||
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export default { | ||
meta: { | ||
docs: { | ||
description: 'Prefer using toThrow for exception tests', | ||
uri: getDocsUrl(__filename), | ||
}, | ||
messages: { | ||
noTryExpect: [ | ||
'Tests should use Jest‘s exception helpers.', | ||
'Use "expect(() => yourFunction()).toThrow()" for synchronous tests,', | ||
'or "await expect(yourFunction()).rejects.toThrow()" for async tests', | ||
].join(' '), | ||
}, | ||
}, | ||
create(context) { | ||
let isTest = false; | ||
let catchDepth = 0; | ||
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function isThrowExpectCall(node) { | ||
return catchDepth > 0 && node.callee.name === 'expect'; | ||
} | ||
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return { | ||
CallExpression(node) { | ||
if (isTestCase(node)) { | ||
isTest = true; | ||
} else if (isTest && isThrowExpectCall(node)) { | ||
context.report({ | ||
messageId: 'noTryExpect', | ||
node, | ||
}); | ||
} | ||
}, | ||
CatchClause() { | ||
if (isTest) { | ||
++catchDepth; | ||
} | ||
}, | ||
'CatchClause:exit'() { | ||
if (isTest) { | ||
--catchDepth; | ||
} | ||
}, | ||
'CallExpression:exit'(node) { | ||
if (isTestCase(node)) { | ||
isTest = false; | ||
} | ||
}, | ||
}; | ||
}, | ||
}; |