@@ -61,3 +61,32 @@ jobs:
 
     - name: Run simple code
       run: python -c 'import math; print(math.factorial(5))'
+
+  setup-pre-release-version-from-manifest:
+    name: Setup 3.9.0-beta.4 ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-latest, windows-latest, ubuntu-16.04, ubuntu-18.04]
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: setup-python 3.9.0-beta.4
+      uses: ./
+      with:
+        python-version: '3.9.0-beta.4'
+
+    - name: Validate version
+      run: |
+        $pythonVersion = (python --version)
+        if ("Python 3.9.0b4" -ne "$pythonVersion"){
+          Write-Host "The current version is $pythonVersion; expected version is 3.9.0b4"
+          exit 1
+        }
+        $pythonVersion
+      shell: pwsh
+
+    - name: Run simple code
+      run: python -c 'import math; print(math.factorial(5))'
@@ -16,6 +16,7 @@ This action sets up a Python environment for use in actions by:
 - Ability to download, install and set up Python packages from `actions/python-versions` that do not come preinstalled on runners
   - Allows for pinning to a specific patch version of Python without the worry of it ever being removed or changed
 - Automatic setup and download of Python packages if using a self-hosted runner
+- Support for pre-release versions of Python
 
 # Usage
 
@@ -92,6 +93,26 @@ jobs:
 
 ```
 
+Download and set up a accurate pre-release version of Python:
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-python@v2
+  with:
+    python-version: '3.9.0-beta.4'
+- run: python my_script.py
+```
+
+Download and set up the latest available version of Python (includes both pre-release and stable versions):
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-python@v2
+  with:
+    python-version: '3.9.0-alpha - 3.9.0' # SemVer's version range syntax
+- run: python my_script.py
+```
+
 # Getting started with Python + Actions
 
 Check out our detailed guide on using [Python with GitHub Actions](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/using-python-with-github-actions).
 
@@ -0,0 +1,52 @@
+[
+    {
+      "version": "1.2.3",
+      "stable": true,
+      "release_url": "https://github.com/actions/sometool/releases/tag/1.2.3-20200402.6",
+      "files": [
+        {
+          "filename": "sometool-1.2.3-linux-x64.tar.gz",
+          "arch": "x64",
+          "platform": "linux",
+          "download_url": "https://github.com/actions/sometool/releases/tag/1.2.3-20200402.6/sometool-1.2.3-linux-x64.tar.gz"
+        },
+        {
+          "filename": "sometool-1.2.3-darwin-x64.tar.gz",
+          "arch": "x64",
+          "platform": "darwin",
+          "download_url": "https://github.com/actions/sometool/releases/tag/1.2.3-20200402.6/sometool-1.2.3-darwin-x64.tar.gz"
+        },
+        {
+          "filename": "sometool-1.2.3-win32-x64.tar.gz",
+          "arch": "x64",
+          "platform": "win32",
+          "download_url": "https://github.com/actions/sometool/releases/tag/1.2.3-20200402.6/sometool-1.2.3-win32-x64.tar.gz"
+        }
+      ]
+    },
+    {
+      "version": "1.2.3-beta.2",
+      "stable": false,
+      "release_url": "https://github.com/actions/sometool/releases/tag/1.2.3-beta.2-20200402.5",
+      "files": [
+        {
+          "filename": "sometool-1.2.3-linux-x64.tar.gz",
+          "arch": "x64",
+          "platform": "linux",
+          "download_url": "https://github.com/actions/sometool/releases/tag/1.2.3-beta.2-20200402.5/sometool-1.2.3-linux-x64.tar.gz"
+        },
+        {
+          "filename": "sometool-1.2.3-darwin-x64.tar.gz",
+          "arch": "x64",
+          "platform": "darwin",
+          "download_url": "https://github.com/actions/sometool/releases/tag/1.2.3-20200402.5/sometool-1.2.3-darwin-x64.tar.gz"
+        },
+        {
+          "filename": "sometool-1.2.3-win32-x64.tar.gz",
+          "arch": "x64",
+          "platform": "win32",
+          "download_url": "https://github.com/actions/sometool/releases/tag/1.2.3-20200402.5/sometool-1.2.3-win32-x64.tar.gz"
+        }
+      ]
+    }
+]
@@ -22,7 +22,7 @@ import * as tc from '@actions/tool-cache';
 import * as finder from '../src/find-python';
 import * as installer from '../src/install-python';
 
-const pythonRelease = require('./data/python-release.json');
+const manifestData = require('./data/versions-manifest.json');
 
 describe('Finder tests', () => {
   afterEach(() => {
@@ -38,12 +38,9 @@ describe('Finder tests', () => {
     await finder.findPythonVersion('3.x', 'x64');
   });
 
-  it('Finds Python if it is not installed, but exists in the manifest', async () => {
-    const findSpy: jest.SpyInstance = jest.spyOn(
-      installer,
-      'findReleaseFromManifest'
-    );
-    findSpy.mockImplementation(() => <tc.IToolRelease>pythonRelease);
+  it('Finds stable Python version if it is not installed, but exists in the manifest', async () => {
+    const findSpy: jest.SpyInstance = jest.spyOn(tc, 'getManifestFromRepo');
+    findSpy.mockImplementation(() => <tc.IToolRelease[]>manifestData);
 
     const installSpy: jest.SpyInstance = jest.spyOn(
       installer,
@@ -58,6 +55,28 @@ describe('Finder tests', () => {
     await finder.findPythonVersion('1.2.3', 'x64');
   });
 
+  it('Finds pre-release Python version in the manifest', async () => {
+    const findSpy: jest.SpyInstance = jest.spyOn(tc, 'getManifestFromRepo');
+    findSpy.mockImplementation(() => <tc.IToolRelease[]>manifestData);
+
+    const installSpy: jest.SpyInstance = jest.spyOn(
+      installer,
+      'installCpythonFromRelease'
+    );
+    installSpy.mockImplementation(async () => {
+      const pythonDir: string = path.join(
+        toolDir,
+        'Python',
+        '1.2.3-beta.2',
+        'x64'
+      );
+      await io.mkdirP(pythonDir);
+      fs.writeFileSync(`${pythonDir}.complete`, 'hello');
+    });
+    // This will throw if it doesn't find it in the manifest (because no such version exists)
+    await finder.findPythonVersion('1.2.3-beta.2', 'x64');
+  });
+
   it('Errors if Python is not installed', async () => {
     // This will throw if it doesn't find it in the cache and in the manifest (because no such version exists)
     let thrown = false;