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exceptiontestingjunitkotlinunchecked-exception
Marcus Lanvers
Marcus Lanvers

Reputation: 411

How do I test expected Unchecked Exceptions in Kotlin?

I am trying to write a test in Kotlin that makes sure an unchecked exception is thrown in specific circumstances.

I am trying to use org.junit.jupiter.api.Assertions.assertThrows like this:

assertThrows(MyRuntimeException::class, Executable { myMethodThatThrowsThatException() })

when i try this i get a

Type inference failed compiler error

because my Exception in not a CheckedException but a RuntimeException. Is there any good way to test this behavior without doing the naive try catch?

Upvotes: 3

Views: 5277

Answers (2)

yole
yole

Reputation: 97138

You can use assertFailsWith from the Kotlin standard library:

assertFailsWith<MyRuntimeException> { myMethodThatThrowsThatException() }

Upvotes: 7

zsmb13
zsmb13

Reputation: 89548

The assertThrows method expects a Class as its first parameter, but you're trying to give it a KClass. To fix this, just do the following (as described in the documentation here):

assertThrows(MyRuntimeException::class.java, Executable { myMethodThatThrowsThatException() })

You can also leave out the explicit Executable type:

assertThrows(MyRuntimeException::class.java, { myMethodThatThrowsThatException() })

Or if your method really doesn't take any parameters, you can use a method reference to it:

assertThrows(MyRuntimeException::class.java, ::myMethodThatThrowsThatException)

Upvotes: 4

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