How to get jasmine tests to ignore tabs in multiline string

Question

I have a function that returns a multiline string like so:

example line 1
example line 2
example line 3

and I'd like to be able to write like so:

it('should get the proper data', () => {
  expect(service.getData('foo').toEqual(
  `example line 1
    example line 2
    example line 3`);
});

but of course that will give me this error since the test adds in some whitespace before most lines:

Expected 'example line 1
example line 2
example line 3' to equal 'example line 1
    example line 2
    example line 3'.

Now I obviously know I could just write my tests slightly differently by adding in \n characters, or just manually removing that whitespace, but that looks a bit uglier in my tests.

I'd love it if there were some kind of utility I could use like this:

it('should get the proper data', () => {
  expect(service.getData('foo').toEqual(
  util.safeUnindent(`example line 1
    example line 2
    example line 3`));
});

Is there some kind of add on I can use that will strip out indentations like this in a safe & reliable way, do I just need to roll my own, or should I just use \n characters?

Answer 1

It looks like you have to roll a little of your own (I have not found any out of the box solution).

But a couple of things comes quickly to mind, where the custom matcher is the most elegant, I find.

1. Using toContain to check that expected content is in the returned string
2. Using toMatch - to check using regular expresion (RegEx)
3. Using custom matchers - very reusable and easy to read

See https://jasmine.github.io/api/edge/matchers, https://jasmine.github.io/tutorials/custom_matcher and https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_expressions

Function to test:

function getData(x){
    return `
    example line 1
    example line 2
    example line 3
    `
}

Test setup:

function trimmedLines(untrimmed){
    // trim leading and trailing spaces and newlines and split at inner newlines
    const lines = untrimmed.trim().replace(/^\n+/, '').replace(/\n+$/, '').split('\n')
    const trimmedLines = []
    lines.forEach(line => {
        // trim and add each line to new array
        trimmedLines.push(line.trim())
    });
    // return a trimmed string
    return trimmedLines.join('\n')
}

const customMatchers = {
    ToEqualTrimmed: function(matchersUtil) {
        return {
            compare: function(actual, expected) {
                if (expected === undefined) expected = '';
                const result = { };
                result.pass = matchersUtil.equals(
                    trimmedLines(actual),
                    trimmedLines(expected)
                )

                if (result.pass) {
                    result.message = "Expected " + actual + " to be trimmed equal to" + expected;
                } else {
                    result.message = "Expected " + actual + " to be trimmed equal to" + expected + ' But was not!';
                }
                return result;
            }
        };
    }
};

beforeEach(function() {
    jasmine.addMatchers(customMatchers);
});

describe("Outer test desc", () => {
    it('should get the proper data', () => {
        const output = getData('foo')
        // this fails
        expect(output).toEqual(
          `example line 1
            example line 2
            example line 3`);
        // these 3 pass
        expect(output).toContain('example line 1')
        expect(output).toContain('example line 2')
        expect(output).toContain('example line 3')
        // this passes too
        expect(output).toMatch('[ \n]*example line 1[ \n]*example line 2[ \n]*example line 3[ \n]*');
        // passes too
        expect(output).ToEqualTrimmed(
          `example line 1
            example line 2
            example line 3`);


    });

});

The [ \n]* matches zero or more spaces or newlines.