Why there are some forward slash in the error string? - jestjs

Question

Here is my stdout after I ran my testings.
expect(received).toBe(expected) // Object.is equality
Expected: "child 'path1' fails because ['path1' is not allowed to be empty]"
Received: "child \"path1\" fails because [\"path1\" is not allowed to be empty]"
39 | } catch (error) {
40 | expect(error.name).toBe('ValidationError');
> 41 | expect(error.message).toBe("child 'path1' fails because ['path1' is not allowed to be empty]");
| ^
42 | }
43 | });
44 | });
at Object.<anonymous> (src/__tests__/models/adChannel/googleadwords/AdGroupAd.spec.ts:41:29)
As you can see, the Received value has forward slash \. It doesn't match the Expected value.
I think maybe the string is escaped? I expect the string doesn't have \

Answer 1

Short answer
Change your expect to this:
expect(error.message).toBe('child "path1" fails because ["path1" is not allowed to be empty]');
...and it will work.
Details
JavaScript allows strings to be defined using either single quotes: 'a string' or double quotes: "a string".
From the MDN doc:
Unlike some other languages, JavaScript makes no distinction between single-quoted strings and double-quoted strings
...so it doesn't matter which approach you use.
Single quotes work fine in a string defined with double quotes:
const singleQuotes = "has 'single quotes' in it";
...and the same is true for double quotes in a string defined with single quotes:
const doubleQuotes = 'has "double quotes" in it';
...but single quotes need to be escaped if they are in a string defined with single quotes:
const singleQuotes = 'has \'single quotes\' in it';
...and the same is true for double quotes in a string defined with double quotes:
const doubleQuotes = "has \"double quotes\" in it";
You are seeing escape characters in the Jest output because Jest is formatting the output string with double quotes around it so the double quotes within it need to be escaped.