Ensure expect(function).toThrow()

[rentalhost]

When is possible to determine if the expect(value) is not a function when used with .toThrow(), it must be an error.

const str = "any value";

expect(str).toThrow() // Not works.

const returnStr = () => "any value";

expect(returnStr).toThrow() // Not handle, but is a valid case (if returnStr() throws an exception).

[SimenB]

You get a runtime error (and possibly a type error?) for this already. Not sure if a lint rule is needed?

[rentalhost]

@SimenB there is no type error, as expect() accepts any. The runtime error occur but is not clear enough for "first-time jesters".

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No type error.

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Error itself is clear, but not working as expected, once that I tried to capture it via .toThrow(), but it is thrown before to catch.

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In my opinion, eslint-plugin-jest would do a good job of catching this type of error before the user runs it, as it would be able to predict and fix it. Even a --fix would be feasible by applying a function wrapper.

[G-Rath]

Given that TypeScript currently won't catch this, it might be worth a lint rule but it would have to use TypeScript to determine the type of whatever's been given to expect.