To TDD Or Not To TDD? Round 2

Area.kt

package org.geepawhill.dungeon

import java.lang.Integer.max
import java.lang.Integer.min

data class Area(val west: Int, val north: Int, val east: Int, val south: Int) {

    val longest: Int get() = max(east - west, south - north)
    val size = (east - west) * (south - north)
    
    fun margin(amount: Int): Area {
        return Area(west - amount, north - amount, east + amount, south + amount)
    }

    fun intersects(other: Area): Boolean {
        return !(south < other.north || north > other.south || west > other.east || east < other.west)
    }

    fun contains(coords: Coords): Boolean {
        return intersects(Area(coords.x, coords.y, coords.x, coords.y))
    }

    fun fill(map: Map, type: CellType) {
        for (c in west..east) {
            for (r in north..south) map[c, r] = type
        }
    }

    fun union(other: Area): Area =
        Area(min(west, other.west), min(north, other.north), max(east, other.east), max(south, other.south))

    override fun toString(): String = "($west,$north) - ($east,$south)"

    companion object {
        fun normalized(start: Coords, end: Coords) =
            Area(min(start.x, end.x), min(start.y, end.y), max(start.x, end.x), max(start.y, end.y))
    }
}