"Method com.example.Source.foo(): From non-null returning to null returning breaking change."
            )
            assertHasNoWarning()
            assertHasNoInformation()
        }
    }

    @Test
    fun `from non-null array element returning to null returning is breaking`() {

        checkNotBinaryCompatibleJava(
            v1 = """

                "Method com.example.Source.baz(): From non-null returning to null-unmarked returning breaking change.",
            )
            assertHasNoWarning()
            assertHasNoInformation()
        }
    }

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

        checkBinaryCompatibleJava(
            v1 = """

        checkNotBinaryCompatibleKotlin(
            v2 = """

           $publicKotlinMembers

            const val cathedral = "cathedral"

            """
        ) {

            assertHasNoInformation()
            assertHasNoWarning()
            assertHasErrors(

                // Kotlin file-facade classes are ignored by the @since rule

    ) {

        val isBinaryCompatible = checkFailure == null

        fun assertEmptyReport() {
            assertHasNoError()
            assertHasNoWarning()
            assertHasNoInformation()
        }

        fun assertHasNoError() {
            assertTrue("Has no error (${richReport.errors})", richReport.errors.isEmpty())
        }

        fun assertHasNoWarning() {