Fix x-y swap in rect function

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pixelmanipulator",
-  "version": "5.5.1",
+  "version": "5.5.2",
   "description": "Run any cellular automata on an html5 canvas.",
   "main": "dist/main.js",
   "browser": "dist/browser.js",
@@ -68,6 +68,7 @@
     "@typescript-eslint/eslint-plugin": "^4.0.1",
     "@typescript-eslint/parser": "^4.0.0",
     "ava": "^4.2.0",
+    "ava-fast-check": "^5.0.0",
     "bootstrap-dark-5": "^1.1.3",
     "browserify": "^17.0.0",
     "c8": "^7.11.2",
@@ -78,6 +79,7 @@
     "eslint-plugin-node": "^11.1.0",
     "eslint-plugin-promise": "^4.2.1 || ^5.0.0",
     "eslint-plugin-tsdoc": "^0.2.16",
+    "fast-check": "^2.25.0",
     "fps-control": "^1.0.0",
     "gh-pages": "^3.2.3",
     "parcel": "^2.5.0",

src/lib/neighborhoods.ts

@@ -26,7 +26,7 @@ export type Hitbox=Location[]
 */
 export function rect (topLeft: Location, bottomRight: Location): Location[] {
   const output: Hitbox = []
-  for (let x = topLeft.x; x <= bottomRight.y; x++) {
+  for (let x = topLeft.x; x <= bottomRight.x; x++) {
     for (let y = topLeft.y; y <= bottomRight.y; y++) {
       output.push({ x, y })
     }

tests/lib/test-neighborhoods.ts

@@ -0,0 +1,59 @@
+import { testProp, fc } from 'ava-fast-check'
+import { neighborhoods } from '../../src/lib/pixelmanipulator'
+const { rect } = neighborhoods
+
+testProp(
+  'rect\'s size output is the area',
+  // Maximums provided to ensure reasonable time and memory is spent
+  [fc.integer(), fc.integer(), fc.nat({ max: 25 }), fc.nat({ max: 25 })],
+  (t, x, y, w, h) => {
+    const topLeft = {
+      x,
+      y
+    }
+    const bottomRight = {
+      x: x + w,
+      y: y + h
+    }
+    const expectedArea = (w + 1) * (h + 1) // (0,0) to (1,1) is area of 4
+    const list = rect(topLeft, bottomRight)
+    t.is(list.length, expectedArea)
+  }
+)
+testProp(
+  'return from rect has no duplicates',
+  [fc.integer(), fc.integer(), fc.nat({ max: 25 }), fc.nat({ max: 25 })],
+  (t, x, y, w, h) => {
+    const topLeft = {
+      x,
+      y
+    }
+    const bottomRight = {
+      x: x + w,
+      y: y + h
+    }
+    const list = rect(topLeft, bottomRight).map(pos => JSON.stringify(pos))
+    const set = new Set(list)
+    t.is(list.length, set.size)
+  }
+)
+testProp(
+  'return from rect keeps all values within bounds',
+  [fc.integer(), fc.integer(), fc.nat({ max: 25 }), fc.nat({ max: 25 })],
+  (t, x, y, w, h) => {
+    const topLeft = {
+      x,
+      y
+    }
+    const bottomRight = {
+      x: x + w,
+      y: y + h
+    }
+    const list = rect(topLeft, bottomRight)
+    t.plan(list.length * 2)
+    list.forEach(pos => {
+      t.true(topLeft.x <= pos.x && pos.x <= bottomRight.x)
+      t.true(topLeft.y <= pos.y && pos.y <= bottomRight.y)
+    })
+  }
+)