diff --git a/.github/workflows/download.yml b/.github/workflows/download.yml
index 50390cec..3091ac01 100644
--- a/.github/workflows/download.yml
+++ b/.github/workflows/download.yml
@@ -121,6 +121,20 @@ jobs:
           ref: ${{github.event.pull_request.head.sha || github.sha}}
       - name: Test
         run: cat artifact/sha | grep $GITHUB_SHA
+  download-unarchived:
+    runs-on: ubuntu-latest
+    needs: wait
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - name: Download
+        uses: ./
+        with:
+          workflow: upload.yml
+          name: sha
+          path: artifact-unarchived
+      - name: Test
+        run: cat artifact-unarchived/sha | grep $GITHUB_SHA
   download-multiple:
     runs-on: ubuntu-latest
     needs: wait
@@ -136,6 +150,7 @@ jobs:
           cat artifact/sha | grep $GITHUB_SHA
           cat artifact1/sha1 | grep $GITHUB_SHA
           cat artifact2/sha2 | grep $GITHUB_SHA
+          cat sha/sha | grep $GITHUB_SHA
   download-regexp:
     runs-on: ubuntu-latest
     needs: wait
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 00000000..ce3d745b
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,22 @@
+name: Test
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+      - name: Install dependencies
+        run: npm install
+      - name: Run tests
+        run: npm test
diff --git a/.github/workflows/upload.yml b/.github/workflows/upload.yml
index b5a242d7..85479383 100644
--- a/.github/workflows/upload.yml
+++ b/.github/workflows/upload.yml
@@ -22,6 +22,16 @@ jobs:
         with:
           name: artifact
           path: artifact
+  upload-unarchived:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Dump
+        run: echo $GITHUB_SHA > sha
+      - name: Upload
+        uses: actions/upload-artifact@v7
+        with:
+          path: sha
+          archive: false
   upload-multiple:
     runs-on: ubuntu-latest
     steps:
diff --git a/main.js b/main.js
index a9a385c5..2cfaebe5 100644
--- a/main.js
+++ b/main.js
@@ -6,6 +6,14 @@ import AdmZip from 'adm-zip'
 import { filesize } from 'filesize'
 import pathname from 'node:path'
 import fs from 'node:fs'
+import { fileURLToPath } from 'node:url'
+
+export function isZipContentType(contentType) {
+    const mimeType = (contentType || '').split(';')[0].trim().toLowerCase()
+    return mimeType === 'application/zip' ||
+           mimeType === 'application/x-zip-compressed' ||
+           mimeType === 'application/zip-compressed'
+}
 
 async function downloadAction(name, path) {
     const artifactClient = artifact.create()
@@ -262,15 +270,16 @@ async function main() {
 
             const size = filesize(artifact.size_in_bytes, { base: 10 })
 
-            core.info(`==> Downloading: ${artifact.name}.zip (${size})`)
+            core.info(`==> Downloading: ${artifact.name} (${size})`)
 
-            let zip
+            let downloadResponse
             try {
-                zip = await client.rest.actions.downloadArtifact({
+                downloadResponse = await client.rest.actions.downloadArtifact({
                     owner: owner,
                     repo: repo,
                     artifact_id: artifact.id,
                     archive_format: "zip",
+                    request: { redirect: 'manual' },
                 })
             } catch (error) {
                 if (error.message.startsWith("Artifact has expired")) {
@@ -280,9 +289,28 @@ async function main() {
                 }
             }
 
+            const blobUrl = downloadResponse.headers.location
+            core.debug(`Download URL: ${blobUrl}`)
+
+            const response = await fetch(blobUrl)
+
+            if (!response.ok) {
+                throw new Error(`Failed to download artifact: ${response.statusText}`)
+            }
+
+            const contentType = response.headers.get('content-type') || ''
+            const urlPath = new URL(blobUrl).pathname.toLowerCase()
+            const urlIndicatesZip = urlPath.endsWith('.zip')
+            const isZipFile = isZipContentType(contentType) || urlIndicatesZip
+
+            core.debug(`Content-Type: ${contentType}, URL path: ${urlPath}, Detected as zip: ${isZipFile}`)
+
+            const buffer = Buffer.from(await response.arrayBuffer())
+
             if (skipUnpack) {
                 fs.mkdirSync(path, { recursive: true })
-                fs.writeFileSync(`${pathname.join(path, artifact.name)}.zip`, Buffer.from(zip.data), 'binary')
+                const ext = isZipFile ? '.zip' : ''
+                fs.writeFileSync(`${pathname.join(path, artifact.name)}${ext}`, buffer, 'binary')
                 continue
             }
 
@@ -290,23 +318,32 @@ async function main() {
 
             fs.mkdirSync(dir, { recursive: true })
 
-            core.startGroup(`==> Extracting: ${artifact.name}.zip`)
-            if (useUnzip) {
-                const zipPath = `${pathname.join(dir, artifact.name)}.zip`
-                fs.writeFileSync(zipPath, Buffer.from(zip.data), 'binary')
-                await exec.exec("unzip", [zipPath, "-d", dir])
-                fs.rmSync(zipPath)
+            if (!isZipFile) {
+                const contentDisposition = response.headers.get('content-disposition') || ''
+                const cdMatch = contentDisposition.match(/filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/)
+                const rawFilename = cdMatch ? cdMatch[1].replace(/^['"]|['"]$/g, '').trim() : artifact.name
+                const filename = pathname.basename(rawFilename) || artifact.name
+                core.info(`==> Writing direct file: ${filename}`)
+                fs.writeFileSync(pathname.join(dir, filename), buffer, 'binary')
             } else {
-                const adm = new AdmZip(Buffer.from(zip.data))
-                adm.getEntries().forEach((entry) => {
-                    const action = entry.isDirectory ? "creating" : "inflating"
-                    const filepath = pathname.join(dir, entry.entryName)
-
-                    core.info(`  ${action}: ${filepath}`)
-                })
-                adm.extractAllTo(dir, true)
+                core.startGroup(`==> Extracting: ${artifact.name}.zip`)
+                if (useUnzip) {
+                    const zipPath = `${pathname.join(dir, artifact.name)}.zip`
+                    fs.writeFileSync(zipPath, buffer, 'binary')
+                    await exec.exec("unzip", [zipPath, "-d", dir])
+                    fs.rmSync(zipPath)
+                } else {
+                    const adm = new AdmZip(buffer)
+                    adm.getEntries().forEach((entry) => {
+                        const action = entry.isDirectory ? "creating" : "inflating"
+                        const filepath = pathname.join(dir, entry.entryName)
+
+                        core.info(`  ${action}: ${filepath}`)
+                    })
+                    adm.extractAllTo(dir, true)
+                }
+                core.endGroup()
             }
-            core.endGroup()
         }
     } catch (error) {
         core.setOutput("found_artifact", false)
@@ -332,4 +369,6 @@ async function main() {
     }
 }
 
-main()
+if (process.argv[1] === fileURLToPath(import.meta.url)) {
+    main()
+}
diff --git a/main.test.js b/main.test.js
new file mode 100644
index 00000000..48a50b78
--- /dev/null
+++ b/main.test.js
@@ -0,0 +1,183 @@
+import { test, describe, beforeEach, afterEach } from 'node:test'
+import assert from 'node:assert/strict'
+import fs from 'node:fs'
+import os from 'node:os'
+import path from 'node:path'
+import AdmZip from 'adm-zip'
+
+// main.js is guarded by import.meta.url so importing it does not call main().
+const { isZipContentType } = await import('./main.js')
+
+// ---------------------------------------------------------------------------
+// isZipContentType – unit tests
+// ---------------------------------------------------------------------------
+
+describe('isZipContentType', () => {
+    test('returns true for application/zip', () => {
+        assert.equal(isZipContentType('application/zip'), true)
+    })
+
+    test('returns true for application/x-zip-compressed', () => {
+        assert.equal(isZipContentType('application/x-zip-compressed'), true)
+    })
+
+    test('returns true for application/zip-compressed', () => {
+        assert.equal(isZipContentType('application/zip-compressed'), true)
+    })
+
+    test('returns true for application/zip with extra parameters', () => {
+        assert.equal(isZipContentType('application/zip; charset=utf-8'), true)
+    })
+
+    test('returns true regardless of case', () => {
+        assert.equal(isZipContentType('Application/Zip'), true)
+        assert.equal(isZipContentType('APPLICATION/ZIP'), true)
+    })
+
+    // archive: false uploads use application/octet-stream or similar
+    test('returns false for application/octet-stream (archive: false direct upload)', () => {
+        assert.equal(isZipContentType('application/octet-stream'), false)
+    })
+
+    test('returns false for text/plain', () => {
+        assert.equal(isZipContentType('text/plain'), false)
+    })
+
+    test('returns false for image/png', () => {
+        assert.equal(isZipContentType('image/png'), false)
+    })
+
+    test('returns false for empty string', () => {
+        assert.equal(isZipContentType(''), false)
+    })
+
+    test('returns false for null', () => {
+        assert.equal(isZipContentType(null), false)
+    })
+
+    test('returns false for undefined', () => {
+        assert.equal(isZipContentType(undefined), false)
+    })
+})
+
+// ---------------------------------------------------------------------------
+// Download behaviour – integration tests using a real temp directory
+// ---------------------------------------------------------------------------
+
+describe('artifact download behaviour', () => {
+    let tmpDir
+
+    beforeEach(() => {
+        tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'artifact-test-'))
+    })
+
+    afterEach(() => {
+        fs.rmSync(tmpDir, { recursive: true, force: true })
+    })
+
+    test('non-ZIP artifact (archive: false) is written as a plain file', () => {
+        // Simulate what main.js does when isZipFile is false:
+        //   fs.writeFileSync(pathname.join(dir, filename), buffer, 'binary')
+        const artifactName = 'my-binary'
+        const content = 'raw file content'
+        const buffer = Buffer.from(content)
+
+        // isZipContentType must return false for a direct-upload content type
+        assert.equal(isZipContentType('application/octet-stream'), false)
+
+        const outputPath = path.join(tmpDir, artifactName)
+        fs.writeFileSync(outputPath, buffer, 'binary')
+
+        assert.ok(fs.existsSync(outputPath), 'output file should exist')
+        assert.equal(fs.readFileSync(outputPath, 'utf8'), content)
+    })
+
+    test('ZIP artifact is extracted to the target directory', () => {
+        // Build a minimal in-memory zip containing one entry
+        const adm = new AdmZip()
+        adm.addFile('hello.txt', Buffer.from('hello from zip'))
+        const zipBuffer = adm.toBuffer()
+
+        // isZipContentType must return true for application/zip
+        assert.equal(isZipContentType('application/zip'), true)
+
+        // Simulate main.js ZIP extraction path (adm-zip branch)
+        const adm2 = new AdmZip(zipBuffer)
+        adm2.extractAllTo(tmpDir, true)
+
+        const extracted = path.join(tmpDir, 'hello.txt')
+        assert.ok(fs.existsSync(extracted), 'extracted file should exist')
+        assert.equal(fs.readFileSync(extracted, 'utf8'), 'hello from zip')
+    })
+
+    test('skip_unpack with non-ZIP writes file without .zip extension', () => {
+        const artifactName = 'my-report'
+        const buffer = Buffer.from('report data')
+        const isZipFile = isZipContentType('application/octet-stream') // false
+
+        const ext = isZipFile ? '.zip' : ''
+        const outputPath = path.join(tmpDir, `${artifactName}${ext}`)
+        fs.writeFileSync(outputPath, buffer, 'binary')
+
+        // Should not have .zip extension
+        assert.ok(fs.existsSync(path.join(tmpDir, 'my-report')), 'file without extension should exist')
+        assert.ok(!fs.existsSync(path.join(tmpDir, 'my-report.zip')), 'file with .zip extension should not exist')
+    })
+
+    test('skip_unpack with ZIP writes file with .zip extension', () => {
+        const adm = new AdmZip()
+        adm.addFile('data.txt', Buffer.from('data'))
+        const artifactName = 'my-archive'
+        const buffer = adm.toBuffer()
+        const isZipFile = isZipContentType('application/zip') // true
+
+        const ext = isZipFile ? '.zip' : ''
+        const outputPath = path.join(tmpDir, `${artifactName}${ext}`)
+        fs.writeFileSync(outputPath, buffer, 'binary')
+
+        assert.ok(fs.existsSync(path.join(tmpDir, 'my-archive.zip')), 'file with .zip extension should exist')
+        assert.ok(!fs.existsSync(path.join(tmpDir, 'my-archive')), 'file without extension should not exist')
+    })
+
+    // -------------------------------------------------------------------------
+    // URL-based ZIP detection
+    // -------------------------------------------------------------------------
+    test('URL path ending with .zip is detected as ZIP', () => {
+        const blobUrl = 'https://storage.example.com/artifact-sha.zip?sig=abc'
+        const urlPath = new URL(blobUrl).pathname.toLowerCase()
+        assert.ok(urlPath.endsWith('.zip'), 'URL pathname should end with .zip')
+    })
+
+    test('URL path not ending with .zip is not detected as ZIP via URL', () => {
+        const blobUrl = 'https://storage.example.com/artifact-sha?sig=abc'
+        const urlPath = new URL(blobUrl).pathname.toLowerCase()
+        assert.ok(!urlPath.endsWith('.zip'), 'URL pathname should not end with .zip')
+    })
+
+    // -------------------------------------------------------------------------
+    // Content-Disposition filename extraction
+    // -------------------------------------------------------------------------
+    test('Content-Disposition filename is used when present', () => {
+        // Simulate the filename extraction logic from main.js
+        function extractFilename(contentDisposition, fallback) {
+            const cdMatch = contentDisposition.match(/filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/)
+            const rawFilename = cdMatch ? cdMatch[1].replace(/^['"]|['"]$/g, '').trim() : fallback
+            return path.basename(rawFilename) || fallback
+        }
+
+        assert.equal(extractFilename('attachment; filename="sha"', 'artifact-name'), 'sha')
+        assert.equal(extractFilename('attachment; filename=sha', 'artifact-name'), 'sha')
+        assert.equal(extractFilename('', 'artifact-name'), 'artifact-name')
+    })
+
+    test('path.basename sanitizes path traversal in artifact name', () => {
+        const dangerousName = '../../../etc/passwd'
+        const safe = path.basename(dangerousName)
+        assert.equal(safe, 'passwd')
+        // Ensure writing to a tmpDir using the sanitized name stays within tmpDir
+        const outputPath = path.join(tmpDir, safe)
+        fs.writeFileSync(outputPath, 'data', 'utf8')
+        assert.ok(fs.existsSync(outputPath))
+    })
+})
+
diff --git a/package.json b/package.json
index 90d24314..d0a56a61 100644
--- a/package.json
+++ b/package.json
@@ -2,6 +2,9 @@
   "name": "action-download-artifact",
   "type": "module",
   "main": "main.js",
+  "scripts": {
+    "test": "node --test main.test.js"
+  },
   "dependencies": {
     "@actions/artifact": "^6.2.0",
     "@actions/core": "^3.0.0",