chore: Add unittests.sh script and update CONTRIBUTING.md

This change introduces a new `unittests.sh` script to simplify running unit tests. The script automatically sets up a minimal test environment, runs `pytest`, and then restores the previous development environment. The CONTRIBUTING.md has been updated to include instructions on using this new script.

Co-authored-by: Liang Wu <wuliang@google.com>
PiperOrigin-RevId: 860222798

Author: wuliang229

CONTRIBUTING.md

@@ -188,6 +188,18 @@ part before or alongside your code PR.
     pytest ./tests/unittests
     ```
 
+    **Alternatively**, use the included `unittests.sh` script which handles
+    environment setup and restoration automatically:
+
+    ```shell
+    ./scripts/unittests.sh
+    ```
+
+    This script will:
+    -   Set up the test environment with minimal dependencies (`test`, `eval`, `a2a`)
+    -   Run the unit tests
+    -   Restore the full development environment (`--all-extras`)
+
 6.  **Auto-format the code:**
 
     **NOTE**: We use `isort` and `pyink` for styles. Use the included

scripts/unittests.sh

@@ -0,0 +1,118 @@
+#!/bin/bash
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# Runs all unit tests for adk codebase. Sets up test environment according to
+# CONTRIBUTING.md.
+# Usage: ./unittests.sh [--version <version>]
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+cd ..
+
+# Argument Parsing
+ALL_VERSIONS=("3.10" "3.11" "3.12" "3.13" "3.14")
+versions_to_run=()
+
+if [[ $# -eq 0 ]]; then
+  versions_to_run=("${ALL_VERSIONS[@]}")
+elif [[ "$1" == "--version" ]]; then
+  if [[ -z "${2:-}" ]]; then
+    echo "Error: Missing version for --version flag." >&2
+    echo "Usage: $0 --version <version>" >&2
+    exit 1
+  fi
+  # Validate version
+  if ! [[ " ${ALL_VERSIONS[*]} " =~ " $2 " ]]; then
+    echo "Error: Invalid version '$2'. Supported versions: ${ALL_VERSIONS[*]}" >&2
+    exit 1
+  fi
+  versions_to_run=("$2")
+else
+  echo "Error: Unknown argument '$1'." >&2
+  echo "Usage: $0 [--version <version>]" >&2
+  exit 1
+fi
+
+
+# Capture original venv for restoration
+ORIGINAL_VENV="${VIRTUAL_ENV:-}"
+
+restore_venv() {
+    # Deactivate the unittest_venv if it is active
+    if command -v deactivate &> /dev/null; then
+        deactivate
+    fi
+
+    if [[ -d ".unittest_venv" ]]; then
+        echo "Cleaning up .unittest_venv..."
+        rm -rf .unittest_venv
+    fi
+
+    if [[ -n "$ORIGINAL_VENV" ]]; then
+        echo "Reactivating pre-existing venv: $ORIGINAL_VENV"
+        source "$ORIGINAL_VENV/bin/activate"
+    fi
+}
+
+# Ensure the environment is restored when the script exits.
+trap restore_venv EXIT
+
+# 1. deactivate the current venv
+if [[ -n "${VIRTUAL_ENV:-}" ]]; then
+    echo "Deactivating current venv: $VIRTUAL_ENV"
+    if command -v deactivate &> /dev/null; then
+        deactivate
+    fi
+
+fi
+
+for version in "${versions_to_run[@]}"; do
+    echo ""
+    echo "=================================================="
+    echo " RUNNING TESTS FOR PYTHON $version"
+    echo "=================================================="
+
+    # 2. create a unittest_venv just for unit tests
+    echo "Creating/Using unittest_venv for python${version} in .unittest_venv..."
+    uv venv --python "${version}" .unittest_venv --clear
+    source .unittest_venv/bin/activate
+
+    # 3. perform the unit tests
+    echo "Setting up test environment in .unittest_venv..."
+    uv sync --extra test --extra eval --extra a2a --active
+
+    echo "Running unit tests..."
+    TEST_EXIT_CODE=0
+    pytest ./tests/unittests || TEST_EXIT_CODE=$?
+
+    # 4. report the unit tests status as is
+    if [[ $TEST_EXIT_CODE -ne 0 ]]; then
+        echo ""
+        echo "--------------------------------------------------"
+        echo "Unit tests failed for Python $version with exit code $TEST_EXIT_CODE"
+        echo "--------------------------------------------------"
+        exit $TEST_EXIT_CODE
+    fi
+done
+
+
+# 5. reactivate the pre-existing venv if the unit test succeeds
+echo ""
+echo "--------------------------------------------------"
+echo "Unit tests passed for all specified versions!"
+echo "--------------------------------------------------"