TIL: @NullAndEmptySource in JUnit5

This is a clear case of RTFM!

I wanted to make sure that a function will return null when given a null or empty string and what I ended up doing was something like this:

internal class CreateNameTest {
@ParameterizedTest
@ValueSource(strings = ["null", "", " "])
fun `there is no creation when the provided value is null or empty or blank`(providedValue: String?) {
val value: String? = if (providedValue == "null")
null else
providedValue
assertThat(createName(value), absent())
}
}

@ValueSource does not accept null values so I passed it indirectly!

I didn’t like it so after, finally, reading the JUnit5 documentation I learned that the library had me covered from the beginning by providing three annotations exactly for this use case:

@NullSource, @EmptySource and @NullOrEmptySource are meant to be used whenever we need to check the behavior of our code when given null or empty inputs.

So the test changes to:

internal class CreateNameTest {
@ParameterizedTest
@NullAndEmptySource
@ValueSource(strings = [" "])
fun `there is no creation when the provided value is null or empty or blank`(providedValue: String?) {
assertThat(createName(providedValue), absent())
}
}

PS: for the curious, the absent() is part of the hamkrest library by Nat Pryce (yes, that Nat Pryce)

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