jest-27-expect-message
Add custom message to Jest expects (with support for Jest 27+). This is a drop in replacement for jest-expect-message
.
The original jest-expect-message
will throw this error when used in newer versions of Jest:
"TypeError: matcherResult.message is not a function"
Version 1.0.4 is fully compatible with jest-expect-message
. Starting in version 1.1.0, I'll start including new features and improvement.s
If jest-expect-message
is updated to support Jest 27+, this package will be marked as deprecated.
Problem
In many testing libraries it is possible to supply a custom message for a given expectation, this is currently not possible in Jest.
For example:
test('returns 2 when adding 1 and 1', () => {
expect(1 + 1, 'Woah this should be 2!').toBe(3);
});
This will throw the following error in Jest:
Expect takes at most one argument.
Solution
jest-27-expect-message
allows you to call expect
with a second argument of a String
message.
For example the same test as above:
test('returns 2 when adding 1 and 1', () => {
expect(1 + 1, 'Woah this should be 2!').toBe(3);
});
With jest-27-expect-message
this will fail with your custom error message:
● returns 2 when adding 1 and 1
Custom message:
Woah this should be 2!
expect(received).toBe(expected) // Object.is equality
Expected: 3
Received: 2
Installation
With npm:
npm install --save-dev jest-27-expect-message
With yarn:
yarn add -D jest-27-expect-message
Setup
Add jest-27-expect-message
to your Jest setupFilesAfterEnv
configuration.
See for help
Jest v24+
"jest": {
"setupFilesAfterEnv": ["jest-27-expect-message"]
}
Jest v23-
"jest": {
"setupTestFrameworkScriptFile": "jest-27-expect-message"
}
Usage
-
expect(actual, message)
-
actual
: The value you would normally pass into anexpect
to assert against with a given matcher. -
message
: String, the custom message you want to be printed should theexpect
fail.
-
test('returns 2 when adding 1 and 1', () => {
expect(1 + 1, 'Woah this should be 2!').toBe(3);
});
Contributors
Matt Phillips |
---|