diff --git a/package.json b/package.json
index 265ba81e0..4297eb22f 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
         "build:ui:dev:https": "node packages/ui-default/build --gulp && node --trace-deprecation packages/ui-default/build --dev --https",
         "build:ui:production": "cross-env NODE_OPTIONS=--max_old_space_size=8192 node packages/ui-default/build --gulp && node packages/ui-default/build --production",
         "build:ui:production:webpack": "cross-env NODE_OPTIONS=--max_old_space_size=8192 node packages/ui-default/build --production",
-        "test": "node test/entry.js",
+        "test": "node -r @hydrooj/utils/lib/register packages/utils/tests/subtask.spec.ts && node test/entry.js",
         "benchmark": "cross-env BENCHMARK=true node test/entry.js",
         "lint": "eslint packages plugins modules --ext .ts,.tsx,.jsx --fix",
         "lint:ci": "eslint packages plugins modules --ext .ts,.tsx,.jsx --max-warnings=0",
@@ -33,12 +33,14 @@
     "devDependencies": {
         "@simplewebauthn/typescript-types": "7.4.0",
         "@types/autocannon": "^7.12.5",
+        "@types/chai": "^4",
         "@types/cross-spawn": "^6.0.6",
         "@types/node": "^20.10.0",
         "@types/semver": "^7.5.6",
         "@types/supertest": "^2.0.16",
         "autocannon": "^7.14.0",
         "cac": "^6.7.14",
+        "chai": "^4.3.10",
         "chokidar": "^3.5.3",
         "cross-env": "^7.0.3",
         "cross-spawn": "^7.0.3",
diff --git a/packages/utils/lib/common.ts b/packages/utils/lib/common.ts
index ead3c3936..19605b5ad 100644
--- a/packages/utils/lib/common.ts
+++ b/packages/utils/lib/common.ts
@@ -240,7 +240,7 @@ interface MatchRule {
 
 const SubtaskMatcher: MatchRule[] = [
     {
-        regex: /^(([A-Za-z0-9]*?)(?:(\d*)[-_])?(\d+))\.(in|txt)$/,
+        regex: /^(([A-Za-z0-9._-]*?)(?:(\d*)[-_])?(\d+))\.(in|txt)$/,
         output: [
             (a) => `${a[1]}.out`,
             (a) => `${a[1]}.ans`,
@@ -332,6 +332,7 @@ export function readSubtasksFromFiles(files: string[], config) {
                             memory: config.memory,
                             type,
                             cases: [c],
+                            id: sid,
                         };
                     } else if (!subtask[sid].cases) subtask[sid].cases = [c];
                     else subtask[sid].cases.push(c);
diff --git a/packages/utils/tests/subtask.spec.ts b/packages/utils/tests/subtask.spec.ts
new file mode 100644
index 000000000..3d7298668
--- /dev/null
+++ b/packages/utils/tests/subtask.spec.ts
@@ -0,0 +1,62 @@
+import { expect } from 'chai';
+import { describe, it } from 'node:test';
+import { readSubtasksFromFiles } from '../lib/common';
+
+interface Info {
+    subtask: number;
+    id: number;
+}
+
+function shouldFindTestcase(files: string[], info?: Info) {
+    const subtasks = readSubtasksFromFiles(files, {});
+    if (files.includes('a2_1.in')) console.log(subtasks);
+    expect(subtasks).to.be.lengthOf(1);
+    if (info?.subtask) expect(subtasks[0].id).to.equal(info.subtask);
+    const cases = subtasks.map((i) => i.cases).flat();
+    expect(cases).to.be.lengthOf(1);
+    if (info?.id) expect(cases[0].id).to.deep.equal(info.id);
+}
+
+describe('single case', () => {
+    it('1.in/1.out', () => {
+        shouldFindTestcase(['1.in', '1.out']);
+    });
+    it('1.in/2.ans', () => {
+        shouldFindTestcase(['1.in', '1.ans']);
+    });
+    it('file1.in/file1.out', () => {
+        shouldFindTestcase(['file1.in', 'file1.out']);
+    });
+    it('file.in1/file.ou1', () => {
+        shouldFindTestcase(['file.in1', 'file.ou1']);
+    });
+    it('input1.txt/output1.txt', () => {
+        shouldFindTestcase(['input1.txt', 'output1.txt']);
+    });
+    it('data.1.in/data.1.out', () => {
+        shouldFindTestcase(['data.1.in', 'data.1.out']);
+    });
+});
+describe('subtask', () => {
+    it('1_1.in/1_1.out', () => {
+        shouldFindTestcase(['1_1.in', '1_1.out'], { subtask: 1, id: 1 });
+    });
+    it('a1_1.in/a1_1.out', () => {
+        shouldFindTestcase(['a1_1.in', 'a1_1.out'], { subtask: 1, id: 1 });
+    });
+    it('a01_01.in/a01_01.out', () => {
+        shouldFindTestcase(['a01_01.in', 'a01_01.out'], { subtask: 1, id: 1 });
+    });
+    it('1-1.in/1-1.out', () => {
+        shouldFindTestcase(['1-1.in', '1-1.out'], { subtask: 1, id: 1 });
+    });
+    it('a1-1.in/a1-1.out', () => {
+        shouldFindTestcase(['a1-1.in', 'a1-1.out'], { subtask: 1, id: 1 });
+    });
+    it('subtask_1_1.in/subtask_1_1.out', () => {
+        shouldFindTestcase(['subtask_1_1.in', 'subtask_1_1.out'], { subtask: 1, id: 1 });
+    });
+    it('01sample-01.in/01sample-01.out', () => {
+        shouldFindTestcase(['01sample-01.in', '01sample-01.out'], { subtask: 1, id: 1 });
+    });
+});