)
            assertHasNoInformation()
        }
    }

    @Test
    fun `from null returning to non-null returning is not breaking`() {

        checkBinaryCompatibleKotlin(
            v1 = """
                class Source {
                    val someVal: String? = null
                    fun foo(): String? = null
                }
            """,
            v2 = """

            )
        }

        // with existing non-incubating file-facade class, new members must be annotated with @Incubating and @since
        checkBinaryCompatibleKotlin(
            v1 = """
                val existing = "file-facade-class"
            """,
            v2 = """
                val existing = "file-facade-class"

        enum class AddedEnum {
            FOO;

            $publicMembers
        }
    """

    @Test
    fun `added internal members are filtered from the comparison`() {

        checkBinaryCompatibleKotlin(
            v1 = existingSource,
            v2 = internalSource
        ).assertEmptyReport()
    }

    @Test
    fun `existing internal members made public appear as added`() {

abstract class AbstractBinaryCompatibilityTest {

    @get:Rule
    val tmpDir = TemporaryFolder()

    private
    val rootDir: File
        get() = tmpDir.root

    internal
    fun checkBinaryCompatibleKotlin(@Language("kotlin") v1: String = "", @Language("kotlin") v2: String, block: CheckResult.() -> Unit = {}): CheckResult =
        runKotlinBinaryCompatibilityCheck(v1, v2) {
            assertBinaryCompatible()