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doc: improve assert documentation #22692

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doc: improve assert documentation #22692

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278b1b6
doc: improve assert documentation
BridgeAR Sep 3, 2018
2d152ed
fixup: address comment
BridgeAR Sep 5, 2018
1ed83bf
fixup: address Anna's comment
BridgeAR Sep 5, 2018
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57 changes: 29 additions & 28 deletions doc/api/assert.md
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Original file line number Diff line number Diff line change
Expand Up @@ -408,19 +408,19 @@ parameter is undefined, a default error message is assigned. If the `message`
parameter is an instance of an [`Error`][] then it will be thrown instead of the
`AssertionError`.

## assert.doesNotReject(block[, error][, message])
## assert.doesNotReject(asyncFn[, error][, message])
<!-- YAML
added: v10.0.0
-->
* `block` {Function|Promise}
* `asyncFn` {Function|Promise}
* `error` {RegExp|Function}
* `message` {string|Error}
* `message` {string}

Awaits the `block` promise or, if `block` is a function, immediately calls the
function and awaits the returned promise to complete. It will then check that
the promise is not rejected.
Awaits the `asyncFn` promise or, if `asyncFn` is a function, immediately
calls the function and awaits the returned promise to complete. It will then
check that the promise is not rejected.

If `block` is a function and it throws an error synchronously,
If `asyncFn` is a function and it throws an error synchronously,
`assert.doesNotReject()` will return a rejected `Promise` with that error. If
the function does not return a promise, `assert.doesNotReject()` will return a
rejected `Promise` with an [`ERR_INVALID_RETURN_VALUE`][] error. In both cases
Expand Down Expand Up @@ -455,7 +455,7 @@ assert.doesNotReject(Promise.reject(new TypeError('Wrong value')))
});
```

## assert.doesNotThrow(block[, error][, message])
## assert.doesNotThrow(fn[, error][, message])
<!-- YAML
added: v0.1.21
changes:
Expand All @@ -466,18 +466,18 @@ changes:
pr-url: https://github.com/nodejs/node/pull/3276
description: The `error` parameter can now be an arrow function.
-->
* `block` {Function}
* `fn` {Function}
* `error` {RegExp|Function}
* `message` {string|Error}
* `message` {string}

Asserts that the function `block` does not throw an error.
Asserts that the function `fn` does not throw an error.

Please note: Using `assert.doesNotThrow()` is actually not useful because there
is no benefit by catching an error and then rethrowing it. Instead, consider
adding a comment next to the specific code path that should not throw and keep
error messages as expressive as possible.

When `assert.doesNotThrow()` is called, it will immediately call the `block`
When `assert.doesNotThrow()` is called, it will immediately call the `fn`
function.

If an error is thrown and it is the same type as that specified by the `error`
Expand Down Expand Up @@ -964,19 +964,19 @@ assert(0);
// assert(0)
```

## assert.rejects(block[, error][, message])
## assert.rejects(asyncFn[, error][, message])
<!-- YAML
added: v10.0.0
-->
* `block` {Function|Promise}
* `asyncFn` {Function|Promise}
* `error` {RegExp|Function|Object|Error}
* `message` {string|Error}
* `message` {string}

Awaits the `block` promise or, if `block` is a function, immediately calls the
function and awaits the returned promise to complete. It will then check that
the promise is rejected.
Awaits the `asyncFn` promise or, if `asyncFn` is a function, immediately
calls the function and awaits the returned promise to complete. It will then
check that the promise is rejected.

If `block` is a function and it throws an error synchronously,
If `asyncFn` is a function and it throws an error synchronously,
`assert.rejects()` will return a rejected `Promise` with that error. If the
function does not return a promise, `assert.rejects()` will return a rejected
`Promise` with an [`ERR_INVALID_RETURN_VALUE`][] error. In both cases the error
Expand All @@ -991,7 +991,7 @@ each property will be tested for including the non-enumerable `message` and
`name` properties.

If specified, `message` will be the message provided by the `AssertionError` if
the block fails to reject.
the `asyncFn` fails to reject.

```js
(async () => {
Expand Down Expand Up @@ -1063,7 +1063,7 @@ If the values are not strictly equal, an `AssertionError` is thrown with a
`message` parameter is an instance of an [`Error`][] then it will be thrown
instead of the `AssertionError`.

## assert.throws(block[, error][, message])
## assert.throws(fn[, error][, message])
<!-- YAML
added: v0.1.21
changes:
Expand All @@ -1078,11 +1078,11 @@ changes:
pr-url: https://github.com/nodejs/node/pull/3276
description: The `error` parameter can now be an arrow function.
-->
* `block` {Function}
* `fn` {Function}
* `error` {RegExp|Function|Object|Error}
* `message` {string|Error}
* `message` {string}

Expects the function `block` to throw an error.
Expects the function `fn` to throw an error.

If specified, `error` can be a [`Class`][], [`RegExp`][], a validation function,
a validation object where each property will be tested for strict deep equality,
Expand All @@ -1091,8 +1091,9 @@ equality including the non-enumerable `message` and `name` properties. When
using an object, it is also possible to use a regular expression, when
validating against a string property. See below for examples.

If specified, `message` will be the message provided by the `AssertionError` if
the block fails to throw.
If specified, `message` will be appended to the message provided by the
`AssertionError` if the `fn` call fails to throw or in case the error validation
fails.

Custom validation object/error instance:

Expand Down Expand Up @@ -1258,12 +1259,12 @@ second argument. This might lead to difficult-to-spot errors.
[`WeakSet`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet
[`assert.deepEqual()`]: #assert_assert_deepequal_actual_expected_message
[`assert.deepStrictEqual()`]: #assert_assert_deepstrictequal_actual_expected_message
[`assert.doesNotThrow()`]: #assert_assert_doesnotthrow_block_error_message
[`assert.doesNotThrow()`]: #assert_assert_doesnotthrow_fn_error_message
[`assert.notDeepStrictEqual()`]: #assert_assert_notdeepstrictequal_actual_expected_message
[`assert.notStrictEqual()`]: #assert_assert_notstrictequal_actual_expected_message
[`assert.ok()`]: #assert_assert_ok_value_message
[`assert.strictEqual()`]: #assert_assert_strictequal_actual_expected_message
[`assert.throws()`]: #assert_assert_throws_block_error_message
[`assert.throws()`]: #assert_assert_throws_fn_error_message
[`strict mode`]: #assert_strict_mode
[Abstract Equality Comparison]: https://tc39.github.io/ecma262/#sec-abstract-equality-comparison
[Object.prototype.toString()]: https://tc39.github.io/ecma262/#sec-object.prototype.tostring
Expand Down