JSON objects with duplicated properties should fail validity and equality checks

Which version of Kotest are you using 5.3.2

I want to verify that a JSON object does not contain duplicated fields. However shouldBeValidJson() and shouldEqualJson() do not throw errors.

I would like an additional comparison flag added to shouldBeValidJson() and compareJsonOptions { } for verifying that properties are distinct.

import io.kotest.assertions.json.CompareMode
import io.kotest.assertions.json.FieldComparison
import io.kotest.assertions.json.PropertyOrder
import io.kotest.assertions.json.TypeCoercion
import io.kotest.assertions.json.compareJsonOptions
import io.kotest.assertions.json.shouldBeValidJson
import io.kotest.assertions.json.shouldEqualJson
import org.junit.jupiter.api.Test

class JsonTest {
    @Test
    fun `expect json with duplicated properties is invalid`() {
        """
            {
              "test": 123,
              "test": 456
            }
        """.trimIndent().shouldBeValidJson()
    }

    @Test
    fun `expect json with duplicated properties does not match de-duplicated object`() {
        """
            {
              "test": 123,
              "test": 456
            }
        """.trimIndent().shouldEqualJson(
            """
                {
                  "test": 456
                }
            """.trimIndent(),
            compareJsonOptions {
                propertyOrder = PropertyOrder.Strict
                fieldComparison = FieldComparison.Strict
            }
        )
    }
}

[Kantis]

Did I correctly identify the changes that should be done

Yes, I think so

Since there are no options yet available for shouldBeValidJson, I doubt that creating an object would be useful but what do you think?

I think it’s still worthwhile since it enables the syntax:

actual shouldBeValidJson {
  allowDuplicateProperties = false
  expected
}

as discussed here: https://github.com/kotest/kotest/issues/3161#issuecomment-1215835513

[Lysoun]

I’ve been working on this check on the kotlinx serialization side (https://github.com/Kotlin/kotlinx.serialization/issues/1990). Once I’m done, it should be a piece of cake to use those checks in kotest 😄