diff --git a/ui/game/src/view/status.ts b/ui/game/src/view/status.ts
index 24e3f7e9909f2..e4a6403a5214e 100644
--- a/ui/game/src/view/status.ts
+++ b/ui/game/src/view/status.ts
@@ -1,7 +1,9 @@
 import { FEN } from 'chessground/types';
 import { Ctrl } from '../interfaces';
 
-function bishopOnColor(expandedFen: string, offset: 0 | 1): boolean {
+export function bishopOnColor(expandedFen: string, offset: 0 | 1): boolean {
+  if (expandedFen.length !== 64) throw new Error('Expanded FEN expected to be 64 characters');
+
   for (let row = 0; row < 8; row++) {
     for (let col = row % 2 === offset ? 0 : 1; col < 8; col += 2) {
       if (/[bB]/.test(expandedFen[row * 8 + col])) return true;
@@ -10,7 +12,14 @@ function bishopOnColor(expandedFen: string, offset: 0 | 1): boolean {
   return false;
 }
 
-function insufficientMaterial(variant: VariantKey, fullFen: FEN): boolean {
+export function expandFen(fullFen: FEN): string {
+  return fullFen
+    .split(' ')[0]
+    .replace(/\d/g, n => '1'.repeat(+n))
+    .replace(/\//g, '');
+}
+
+export function insufficientMaterial(variant: VariantKey, fullFen: FEN): boolean {
   // TODO: atomic and antichess
   if (
     variant === 'horde' ||
@@ -18,18 +27,17 @@ function insufficientMaterial(variant: VariantKey, fullFen: FEN): boolean {
     variant === 'racingKings' ||
     variant === 'crazyhouse' ||
     variant === 'atomic' ||
-    variant === 'antichess'
+    variant === 'antichess' ||
+    variant === 'threeCheck'
   )
     return false;
-  let fen = fullFen.split(' ')[0].replace(/[^a-z]/gi, '');
-  if (/^[Kk]{2}$/.test(fen)) return true;
-  if (variant === 'threeCheck') return false;
-  if (/[prq]/i.test(fen)) return false;
-  if (/n/.test(fen)) return fen.length - fen.replace(/[a-z]/g, '').length <= 2 && !/[PBNR]/.test(fen);
-  if (/N/.test(fen)) return fen.length - fen.replace(/[A-Z]/g, '').length <= 2 && !/[pbnr]/.test(fen);
-  if (/b/i.test(fen)) {
-    for (let i = 8; i > 1; i--) fen = fen.replace('' + i, '1' + (i - 1));
-    return (!bishopOnColor(fen, 0) || !bishopOnColor(fen, 1)) && !/[pPnN]/.test(fen);
+  const pieces = fullFen.split(' ')[0].replace(/[^a-z]/gi, '');
+  if (/^[Kk]{2}$/.test(pieces)) return true;
+  if (/[prq]/i.test(pieces)) return false;
+  if (/^[KkNn]{3}$/.test(pieces)) return true;
+  if (/b/i.test(pieces)) {
+    const expandedFen = expandFen(fullFen);
+    return (!bishopOnColor(expandedFen, 0) || !bishopOnColor(expandedFen, 1)) && !/[pPnN]/.test(pieces);
   }
   return false;
 }
diff --git a/ui/game/tests/status.test.ts b/ui/game/tests/status.test.ts
new file mode 100644
index 0000000000000..028cf4604a7a5
--- /dev/null
+++ b/ui/game/tests/status.test.ts
@@ -0,0 +1,101 @@
+import { describe, expect, test } from 'vitest';
+import { bishopOnColor, expandFen, insufficientMaterial } from '../src/view/status';
+
+describe('expand fen', () => {
+  test('starting position', () =>
+    expect(expandFen('rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1')).toBe(
+      'rnbqkbnrpppppppp11111111111111111111111111111111PPPPPPPPRNBQKBNR',
+    ));
+  test('middlegame position', () =>
+    expect(expandFen('r2q1rk1/p3ppbp/2pp1np1/2n5/2P3b1/1P1BPN2/PB1N1PPP/2RQ1RK1 w HAhq - 0 1')).toBe(
+      'r11q1rk1p111ppbp11pp1np111n1111111P111b11P1BPN11PB1N1PPP11RQ1RK1',
+    ));
+});
+
+describe('bishop on color', () => {
+  test('bishop on square', () => {
+    expect(bishopOnColor(expandFen('B7/8/8/8/8/8/8/8 w - - 0 1'), 0)).toBe(true);
+    expect(bishopOnColor(expandFen('2B5/8/8/8/8/8/8/8 w - - 0 1'), 0)).toBe(true);
+    expect(bishopOnColor(expandFen('3B4/8/8/8/8/8/8/8 w - - 0 1'), 1)).toBe(true);
+    expect(bishopOnColor(expandFen('2BB4/8/8/8/8/8/8/8 w - - 0 1'), 1)).toBe(true);
+  });
+  test('no bishops on black squares', () => {
+    expect(bishopOnColor(expandFen('B7/8/8/8/8/8/8/8 w - - 0 1'), 1)).toBe(false);
+    expect(bishopOnColor(expandFen('2B5/8/8/8/8/8/8/8 w - - 0 1'), 1)).toBe(false);
+    expect(bishopOnColor(expandFen('5K2/8/8/1B6/8/k7/6b1/8 w - - 0 39'), 1)).toBe(false);
+  });
+});
+
+describe('test insufficient material', () => {
+  test('K vs K', () => expect(insufficientMaterial('standard', '4k3/8/8/8/8/8/8/4K3 w - - 0 1')).toBe(true));
+
+  test('KB vs K', () =>
+    expect(insufficientMaterial('standard', '4k3/8/8/8/8/8/8/4KB2 w - - 0 1')).toBe(true));
+
+  test('KBB vs K (same color bishops)', () =>
+    expect(insufficientMaterial('standard', '4k3/8/8/8/8/8/6B1/4K2B w - - 0 1')).toBe(true));
+
+  test('KB vs KB (same color bishops)', () =>
+    expect(insufficientMaterial('standard', 'k7/8/1b6/8/8/8/1B6/K7 w - - 0 1')).toBe(true));
+});
+
+describe('should not be insufficient material', () => {
+  test.each<VariantKey[]>([
+    ['horde'],
+    ['kingOfTheHill'],
+    ['racingKings'],
+    ['crazyhouse'],
+    ['atomic'],
+    ['antichess'],
+    ['threeCheck'],
+  ])('variant %s', variant =>
+    expect(insufficientMaterial(variant, 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1')).toBe(
+      false,
+    ),
+  );
+
+  test('pawn is never insufficient material', () =>
+    expect(insufficientMaterial('standard', '4k3/8/8/8/8/8/7P/4K3 w - - 0 1')).toBe(false));
+
+  test('rook is never insufficient material', () =>
+    expect(insufficientMaterial('standard', '4k3/8/8/8/8/8/7R/4K3 w - - 0 1')).toBe(false));
+
+  test('queen is never insufficient material', () =>
+    expect(insufficientMaterial('standard', '4k3/8/8/8/8/8/7Q/4K3 w - - 0 1')).toBe(false));
+
+  test('KBB vs K (diff color bishops)', () => {
+    expect(insufficientMaterial('standard', '8/8/1B6/8/1KB5/8/2k5/8 b - - 100 103')).toBe(false);
+    expect(insufficientMaterial('standard', '8/8/1B6/8/1KB5/8/2k5/8')).toBe(false);
+  });
+
+  test('KB vs KN', () =>
+    expect(insufficientMaterial('standard', 'kn6/8/8/8/8/8/8/KB6 w - - 0 1')).toBe(false));
+
+  test('KB vs KB (diff color bishops)', () =>
+    expect(insufficientMaterial('standard', 'k7/1b6/8/8/8/8/1B6/K7 w - - 0 1')).toBe(false));
+});
+
+describe('knight rules', () => {
+  test('KN vs K', () => expect(insufficientMaterial('standard', 'k7/8/1n6/8/8/8/8/K7 w - - 0 1')).toBe(true));
+  test('KNN vs K', () =>
+    expect(insufficientMaterial('standard', 'k7/8/1nn5/8/8/8/8/K7 w - - 0 1')).toBe(false));
+});
+
+describe('scalachess fens from AutodrawTest.scala', () => {
+  test.each([['5K2/8/8/1B6/8/k7/6b1/8 w - - 0 39']])('should detect insufficient material', fen => {
+    expect(insufficientMaterial('standard', fen)).toBe(true);
+  });
+
+  test.each([
+    ['1n2k1n1/8/8/8/8/8/8/4K3 w - - 0 1'],
+    ['7K/5k2/7P/6n1/8/8/8/8 b - - 0 40'],
+    ['1b1b3K/8/5k1P/8/8/8/8/8 b - - 0 40'],
+    ['b2b3K/8/5k1Q/8/8/8/8/8 b - -'],
+    ['1b1b3K/8/5k1Q/8/8/8/8/8 b - -'],
+    ['8/8/5N2/8/6p1/8/5K1p/7k w - - 0 37'],
+    ['8/8/8/4N3/4k1p1/6K1/8/3b4 w - - 5 59'],
+    ['8/8/3Q4/2bK4/B7/8/8/k7 b - - 0 67'],
+  ])('should not detect insufficient material', fen => {
+    expect(insufficientMaterial('standard', fen)).toBe(false);
+  });
+});