Testing Front-End Developers

Today i was given the task of writing up a test for a couple of new developers applying for a front-end development role. Usually ( most of the times i've been tested ) it has been a boring 'cut up this PSD and include sprinkles some $ on it. However I feel like this is in no way a useful representation of the a front-end developer's skillset and they don't really take away anything from it either. ( if anything it may deter them from the work ). So i wrote up a purely javascript/basic DOM manipulation test that goes as follows:

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Make a blank html page with a single text input and an empty list.

While you type into this input, every time a user writes an operation, add it to an object called 'OperationHistory' where the operation is the Property Name and the result of the operation is the property. Then clear the input. If there is a syntax error or maths error; the property must be 'error'.

*operation = any basic arithmetic followed by '#end#'. Limit character input to only accept integers and operators.

Every 1000 milliseconds, run a function that will determine the highest result in 'OperationHistory' and append this outcome and the operation itself to the list in the following format:

"the following maths problem :" + operation + " = " + outcome + " yielded the highest result so far."

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I guess it's not a great test but i'm purely interested in the javascript ability of the candidates and i couldn't find anything on google quickly that couldn't be solved quickly by looking it up or SO-ing the problem.

Which brings me to my main issue;

Where is a resource of cool nonsense tests that I could give to a budding developer and adequately measure their 'real-world' front-end ability?

OR

Are there any great resources that help out with this sort of thing?