I am writing some unit tests for a codebase which uses octal literals. Whenever the test is executed with npm test, a syntax error appears as follows:
Legacy octal literals are not allowed in strict mode.
I should stress that "use strict" does not appear anywhere in the source code, nor can I identify any option in package-lock.json or package.json indicating strict mode. Both JSON files were created with the npm init -y and received no further modification except the addition of:
"scripts": {
"test": "jest"
},
How can I force Jest out of strict mode in order to test code with legacy octal literals?
Per the docs:
By default, Jest will use
babel-jesttransformer
You can explicitly tell Jest you don't want it to try to apply any transforms by setting the following Jest configuration (e.g. in jest.config.<ext> or under $.jest in the package file):
"transform": {}
See full example below. Alternatively, you can leave Babel's transforms active but configure it with "sourceType": "script".
package.json:
{
"name": "strict-jest",
"version": "0.1.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "jest"
},
"keywords": [],
"author": "",
"license": "ISC",
"devDependencies": {
"jest": "^28.1.2"
},
"jest": {
"transform": {}
}
}
index.test.js:
it("works", () => {
expect(0100).toEqual(64);
});
Output:
$ npm t
> strict-jest@0.1.0 test
> jest
PASS ./index.test.js
✓ works (2 ms)
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 0.257 s
Ran all test suites.