implemented tests for reorderElements

.gitignore

@@ -130,3 +130,4 @@ dist
 .yarn/install-state.gz
 .pnp.*
 
+.tap

package.json

@@ -7,6 +7,7 @@
         "start-release": "npm run build && serve dist",
         "lint": "eslint \"{src,test}/**/*.{ts,tsx}\"",
         "typecheck": "tsc --noEmit",
+        "test": "tap run",
         "prebuild": "npm run lint && npm run typecheck",
         "preview": "vite preview"
     },
@@ -38,6 +39,7 @@
         "eslint-plugin-react": "^7.33.2",
         "eslint-plugin-react-hooks": "^4.6.0",
         "serve": "^14.2.1",
+        "tap": "^18.6.1",
         "typescript": "^5.2.2",
         "vite": "^4.3.2"
     }

src/shared/collections.test.ts

@@ -0,0 +1,49 @@
+import t from 'tap';
+import { reorderElements } from './collections.js';
+
+void t.test('reorderElements', (t) => {
+    const checkReordering = (
+        oldIndex: number,
+        newIndex: number,
+        expected: string,
+    ) => {
+        t.match(
+            reorderElements('abcde'.split(''), oldIndex, newIndex),
+            expected.split(''),
+        );
+    };
+
+    checkReordering(0, -1, 'bcde');
+    checkReordering(1, -1, 'acde');
+    checkReordering(2, -1, 'abde');
+    checkReordering(3, -1, 'abce');
+    checkReordering(4, -1, 'abcd');
+    checkReordering(5, -1, 'abcde');
+
+    checkReordering(0, 0, 'abcde');
+    checkReordering(0, 1, 'bacde');
+    checkReordering(0, 2, 'bcade');
+    checkReordering(0, 3, 'bcdae');
+    checkReordering(0, 4, 'bcdea');
+    checkReordering(1, 0, 'bacde');
+    checkReordering(1, 1, 'abcde');
+    checkReordering(1, 2, 'acbde');
+    checkReordering(1, 3, 'acdbe');
+    checkReordering(1, 4, 'acdeb');
+    checkReordering(2, 0, 'cabde');
+    checkReordering(2, 1, 'acbde');
+    checkReordering(2, 2, 'abcde');
+    checkReordering(2, 3, 'abdce');
+    checkReordering(2, 4, 'abdec');
+    checkReordering(3, 0, 'dabce');
+    checkReordering(3, 1, 'adbce');
+    checkReordering(3, 2, 'abdce');
+    checkReordering(3, 3, 'abcde');
+    checkReordering(3, 4, 'abced');
+    checkReordering(4, 0, 'eabcd');
+    checkReordering(4, 1, 'aebcd');
+    checkReordering(4, 2, 'abecd');
+    checkReordering(4, 3, 'abced');
+    checkReordering(4, 4, 'abcde');
+    t.end();
+});