diff --git a/.github/workflows/lab-autograding.yml b/.github/workflows/lab-autograding.yml
index 918d29b8..52f68ea6 100644
--- a/.github/workflows/lab-autograding.yml
+++ b/.github/workflows/lab-autograding.yml
@@ -12,8 +12,9 @@ jobs:
                 os: [ubuntu-22.04]
             fail-fast: false
         steps:
-            - uses: actions/checkout@v1
+            - uses: actions/checkout@v4
               with:
+                  ref: "${{ github.event.pull_request.merge_commit_sha }}"
                   fetch-depth: 1
             - uses: actions/setup-node@v4
               with:
diff --git a/lab3/README.md b/lab3/README.md
new file mode 100644
index 00000000..f95c2ca0
--- /dev/null
+++ b/lab3/README.md
@@ -0,0 +1,29 @@
+# Lab3
+
+## Introduction
+
+In this lab, you will write unit tests for functions implemented in `main.js`. You can learn how to use classes and functions in it by uncommenting the code in it. (But remember don't commit them on GitHub)
+
+## Preparation (Important!!!)
+
+1. Sync fork on GitHub
+2. `git checkout -b lab3` (**NOT** your student ID !!!)
+
+## Requirement
+
+1. (40%) Write test cases in `main_test.js` and achieve 100% code coverage.
+2. (30%) For each function, parameterize their testcases to test the error-results.
+3. (30%) For each function, use at least 3 parameterized testcases to test the non-error-results.
+
+You can run `validate.sh` in your local to test if you satisfy the requirements.
+
+Please note that you must not alter files other than `main_test.js`. You will get 0 points if
+
+1. you modify other files to achieve requirements.
+2. you can't pass all CI on your PR.
+
+## Submission
+
+You need to open a pull request to your branch (e.g. 311XXXXXX, your student number) and contain the code that satisfies the abovementioned requirements.
+
+Moreover, please submit the URL of your PR to E3. Your submission will only be accepted when you present at both places.
diff --git a/lab3/main.js b/lab3/main.js
new file mode 100644
index 00000000..cee5de7f
--- /dev/null
+++ b/lab3/main.js
@@ -0,0 +1,34 @@
+class Calculator {
+    exp(x) {
+        if (!Number.isFinite(x)) {
+            throw Error('unsupported operand type');
+        }
+        const result = Math.exp(x);
+        if (result === Infinity) {
+            throw Error('overflow');
+        }
+        return result;
+    }
+
+    log(x) {
+        if (!Number.isFinite(x)) {
+            throw Error('unsupported operand type');
+        }
+        const result = Math.log(x);
+        if (result === -Infinity) {
+            throw Error('math domain error (1)');
+        }
+        if (Number.isNaN(result)) {
+            throw Error('math domain error (2)');
+        }
+        return result;
+    }
+}
+
+// const calculator = new Calculator();
+// console.log(calculator.exp(87));
+// console.log(calculator.log(48763));
+
+module.exports = {
+    Calculator
+};
\ No newline at end of file
diff --git a/lab3/main_test.js b/lab3/main_test.js
new file mode 100644
index 00000000..e6d6414e
--- /dev/null
+++ b/lab3/main_test.js
@@ -0,0 +1,5 @@
+const {describe, it} = require('node:test');
+const assert = require('assert');
+const { Calculator } = require('./main');
+
+// TODO: write your tests here
diff --git a/lab3/validate.sh b/lab3/validate.sh
new file mode 100755
index 00000000..7a758fb3
--- /dev/null
+++ b/lab3/validate.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# Check for unwanted files
+for file in *; do
+  if [[ $file != "main.js" && $file != "main_test.js" && $file != "README.md" && $file != "validate.sh" ]]; then
+    echo "[!] Unwanted file detected: $file."
+    exit 1
+  fi
+done
+
+node=$(which node)
+test_path="${BASH_SOURCE[0]}"
+solution_path="$(realpath .)"
+tmp_dir=$(mktemp -d -t lab3-XXXXXXXXXX)
+
+cd $tmp_dir
+
+rm -rf *
+cp $solution_path/*.js .
+result=$($"node" --test --experimental-test-coverage) ; ret=$?
+if [ $ret -ne 0 ] ; then
+  echo "[!] testing fails"
+  exit 1
+else
+  coverage=$(echo "$result" | grep 'all files' | awk -F '|' '{print $2}' | sed 's/ //g')
+  if (( $(echo "$coverage < 100" | bc -l) )); then
+    echo "[!] Coverage is only $coverage%"
+    exit 1
+  else
+    echo "[V] Coverage is 100%"
+  fi
+fi
+
+rm -rf $tmp_dir
+
+exit 0
+
+# vim: set fenc=utf8 ff=unix et sw=2 ts=2 sts=2:
\ No newline at end of file