Expect expression not to throw any error using Chai

Question

I have a function

export function getFileContent(path: string): any {
    const content = readFileSync(path);
    return JSON.parse(content.toString());
}

If I want to check if the expression getFileContent(meteFile) throws some definite error I should write something like

expect(getFileContent(meteFile)).to.throw(new SyntaxError('Unexpected token } in JSON at position 82'));

But is there a way to check if the expression doesn't raise any error?

I tried this

expect(getFileContent(metaFile)).not.to.throw(); 

But got the error

AssertionError: expected { Object (...) } to be a function

So how can I check if the function call doesn't throw any error?

Answer 1

You can check if the function call doesn't throw an error using assert.doesNotThrow method

Here is an example from the documentation

assert.doesNotThrow(fn, 'Any Error thrown must not have this message');
assert.doesNotThrow(fn, /Any Error thrown must not match this/);
assert.doesNotThrow(fn, Error);
assert.doesNotThrow(fn, errorInstance);

For further understanding checkout it's documentation: assert.doesNotThrow

Answer 2

It seems like you are using expect , so then you can use expect(fn).to.not.throw to make sure it doesn't throw an error.

expect(myFn).to.not.throw(); // makes sure no errors are thrown
expect(myFn).to.not.throw(SomeCustomError, "the message I expect in that error"); // not recommended by their docs

You should probably look at the docs for this .