Convert ArrayNode to List

[bartsimp]

I'd like to convert a json array into a java List, but I got this error:

Error converting parameter at index 0: No implicit conversion to convert object of type com.fasterxml.jackson.databind.node.ArrayNode to type java.util.List
org.junit.jupiter.api.extension.ParameterResolutionException: Error converting parameter at index 0: No implicit conversion to convert object of type com.fasterxml.jackson.databind.node.ArrayNode to type java.util.List

Here my test:

@ParameterizedTest
@JsonClasspathSource("items.json")
void test1(@Property("items") List<Integer> items) {
    assertFalse(items.isEmpty());
    assertEquals(2, items.size());
}

@ParameterizedTest
@JsonClasspathSource("items.json")
void test2(@Property("items") Integer[] items) {
    assertEquals(2, items.length);
}

items.json:

[
  {
    "items": [ 1, 3 ]
  },
  {
    "items": [ 2, 4 ]
  }
]

what am I missing?

[Michael1993]

Hi @bartsimp!

Unfortunately, I don't have a lot of time right now, but I wanted to call your attention to this issue:
#639

Your problem is in the JSON file.

[beatngu13]

Hey @bartsimp!

We use Jackson as our JSON parser. Jackson creates an ArrayNode from items, which implements Iterable:

@ParameterizedTest
@JsonSource("""
		[
		  {
			"items": [ 1, 3 ]
		  },
		  {
			"items": [ 2, 4 ]
		  }
		]
		""")
void test1(@Property("items") Iterable<Integer> items) {
	assertThat(items).hasSize(2);
}

Alternatively, as suggested by @Michael1993, you can also modify your JSON:

@ParameterizedTest
@JsonSource("""
		[
		  [ 1, 3 ],
		  [ 2, 4 ]
		]
		""")
void test2(List<Integer> items) {
	assertThat(items).hasSize(2);
}

Feel free to reopen this issue if that doesn't help you.

[bartsimp]

@Michael1993, @beatngu13 Thanks for suggestions but I'm afraid is not exactly what I'm looking for...
I'd like to test a method like

public Integer sum(List<Integer> items) {
    return items.stream().reduce(0, Integer::sum);
}

using a json parameterized test which contains also the expected response

@ParameterizedTest
    @JsonSource("""
          [
                {
                  "items": [1, 3],
                  "expectedResult": 4
                },
                {
                  "items": [2, 4],
                  "expectedResult": 6
                }
          ]
          """)
    void testSum(
            @Property("items") List<Integer> items,
            @Property("expectedResult") Integer expectedResult
    ) {
        assertThat(
                new Calculator().sum(items),
                equalTo(expectedResult)
        );
    }

do you think is possible?

[beatngu13]

@bartsimp I actually made a mistake, my suggestion above throws the following exception once you dig a little deeper:

java.lang.ClassCastException: class com.fasterxml.jackson.databind.node.IntNode cannot be cast to class java.lang.Integer

A workaround (I don't like it though):

@ParameterizedTest
@JsonSource("""
		[
			  {
				"items": [1, 3],
				"expectedResult": 4
			  },
			  {
				"items": [2, 4],
				"expectedResult": 6
			  }
		]
		"""
)
void testSum(
		@Property("items") Iterable<IntNode> items,
		@Property("expectedResult") int expectedResult
) {
	List<Integer> itemsList = StreamSupport.stream(items.spliterator(), false)
			.map(IntNode::intValue)
			.toList();
	Integer actualResult = new Calculator().sum(itemsList);
	assertEquals(expectedResult, actualResult);
}

---

The "problem" is this method:

https://github.com/junit-pioneer/junit-pioneer/blob/main/src/main/java/org/junitpioneer/jupiter/json/JacksonNode.java#L64-L88

No case matches, which is why we return node (JsonNode / ArrayNode with IntNodes).

I reopen this issue. I'm not that familiar with the Jackson API, and I'm not sure how type erasure will be a problem here, but I believe we can do better.