diff --git a/Terrain2/Algorithms.swift b/Terrain2/Algorithms.swift
index 0506dc5..526446b 100644
--- a/Terrain2/Algorithms.swift
+++ b/Terrain2/Algorithms.swift
@@ -182,7 +182,7 @@ public class DiamondSquareAlgorithm: Algorithm {
         }
 
         var subdivisions: [Box] {
-            guard size.w > 1 && size.h > 1 else {
+            guard size.w > 2 && size.h > 2 else {
                 return []
             }
             let midp = midpoint
@@ -194,6 +194,15 @@ public class DiamondSquareAlgorithm: Algorithm {
                 Box(origin: (origin.x + newSize.w, origin.y + newSize.h), size: newSize)
             ]
         }
+
+        func breadthFirstSearch(visit: (Box) -> (Void)) {
+            var queue = [self]
+            while queue.count > 0 {
+                let box = queue.removeFirst()
+                visit(box)
+                queue.append(contentsOf: box.subdivisions)
+            }
+        }
     }
     
     let name = "Diamond-Square"
@@ -236,7 +245,7 @@ public class DiamondSquareAlgorithm: Algorithm {
             }
         }
 
-        breadthFirstSearch(ofGridWithSize: size) { (box: Box) in
+        box.breadthFirstSearch { (box: Box) in
             let halfSize = (w: box.size.w / 2 + 1, h: box.size.h / 2 + 1)
 
             // 1. Diamond. Average the corners, add a random value. Set the midpoint.
@@ -281,15 +290,6 @@ public class DiamondSquareAlgorithm: Algorithm {
         texture.replace(region: region, mipmapLevel: 0, withBytes: heightMap, bytesPerRow: MemoryLayout<Float>.stride * size.width)
     }
 
-    private func breadthFirstSearch(ofGridWithSize size: MTLSize, visit: (Box) -> (Void)) {
-        var queue = [Box(origin: (0, 0), size: (size.width, size.height))]
-        while queue.count > 0 {
-            let box = queue.removeFirst()
-            visit(box)
-            queue.append(contentsOf: box.subdivisions)
-        }
-    }
-
     // MARK: Algorithm
 
     var outTexture: MTLTexture {
diff --git a/Terrain2Tests/AlgorithmsTests.swift b/Terrain2Tests/AlgorithmsTests.swift
index ed9d212..17858b1 100644
--- a/Terrain2Tests/AlgorithmsTests.swift
+++ b/Terrain2Tests/AlgorithmsTests.swift
@@ -14,7 +14,43 @@ public typealias Point = DiamondSquareAlgorithm.Box.Point
 public typealias Size = DiamondSquareAlgorithm.Box.Size
 
 class DiamondSquareBFSTests: XCTestCase {
+    func testBFS() {
+        let box = Box(origin: (x: 3, y: 4), size: (w: 5, h: 5))
+        var expectedBoxes: [Box] = [
+            box,
+            Box(origin: (x: 3, y: 4), size: (w: 3, h: 3)),
+            Box(origin: (x: 6, y: 4), size: (w: 3, h: 3)),
+            Box(origin: (x: 3, y: 7), size: (w: 3, h: 3)),
+            Box(origin: (x: 6, y: 7), size: (w: 3, h: 3)),
 
+            Box(origin: (x: 3, y: 4), size: (w: 2, h: 2)),
+            Box(origin: (x: 5, y: 4), size: (w: 2, h: 2)),
+            Box(origin: (x: 3, y: 6), size: (w: 2, h: 2)),
+            Box(origin: (x: 5, y: 6), size: (w: 2, h: 2)),
+
+            Box(origin: (x: 6, y: 4), size: (w: 2, h: 2)),
+            Box(origin: (x: 8, y: 4), size: (w: 2, h: 2)),
+            Box(origin: (x: 6, y: 6), size: (w: 2, h: 2)),
+            Box(origin: (x: 8, y: 6), size: (w: 2, h: 2)),
+
+            Box(origin: (x: 3, y: 7), size: (w: 2, h: 2)),
+            Box(origin: (x: 5, y: 7), size: (w: 2, h: 2)),
+            Box(origin: (x: 3, y: 9), size: (w: 2, h: 2)),
+            Box(origin: (x: 5, y: 9), size: (w: 2, h: 2)),
+
+            Box(origin: (x: 6, y: 7), size: (w: 2, h: 2)),
+            Box(origin: (x: 8, y: 7), size: (w: 2, h: 2)),
+            Box(origin: (x: 6, y: 9), size: (w: 2, h: 2)),
+            Box(origin: (x: 8, y: 9), size: (w: 2, h: 2)),
+        ].reversed()
+
+        box.breadthFirstSearch { (box: Box) -> (Void) in
+            let exBox = expectedBoxes.popLast()
+            XCTAssertNotNil(exBox)
+            XCTAssertEqual(box, exBox!)
+        }
+        XCTAssertEqual(expectedBoxes.count, 0)
+    }
 }
 
 class DiamondSquareBoxTests: XCTestCase {