Error

    A. From kotlin online compiler
    @Test
    fun `Mark way around wall 2`() {
        val mapString = """
        ......X...B.........
        ..........B.........
        ........BBB....S....
        ....................
        """.trimIndent()

        val marked = """
        ......*...B.........
        .......*..B.........
        .......*BBB*****....
        ........***.........
        """.trimIndent()

        assertEquals(marked, addPath(mapString))
    }
    
    B. From the git link
    @Test
    fun `Mark way around wall 2`() {
        val mapString = """
        ..........B.........
        ......X...B.........
        ..........B.........
        ........BBB....S....
        ....................
        """.trimIndent()

        val marked = """
        ..........B.........
        ......*...B.........
        ......*...B.........
        .......*BBB*****....
        ........***.........
        """.trimIndent()

        assertEquals(marked, addPath(mapString))
    }