diff --git a/.github/workflows/abtesting.yml b/.github/workflows/abtesting.yml
index ab2b77aa8d6..f5a2d6f81c0 100644
--- a/.github/workflows/abtesting.yml
+++ b/.github/workflows/abtesting.yml
@@ -45,7 +45,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: ABTesting
-      setup_command: scripts/setup_quickstart_spm.sh abtesting
+      setup_command: scripts/setup_quickstart.sh abtesting
       plist_src_path: scripts/gha-encrypted/qs-abtesting.plist.gpg
       plist_dst_path: quickstart-ios/abtesting/GoogleService-Info.plist
     secrets:
@@ -69,7 +69,7 @@ jobs:
       with:
         python-version: '3.11'
     - name: Setup quickstart
-      run: scripts/setup_quickstart_spm.sh abtesting
+      run: scripts/setup_quickstart.sh abtesting
     - name: Install Secret GoogleService-Info.plist
       run: scripts/decrypt_gha_secret.sh scripts/gha-encrypted/qs-abtesting.plist.gpg \
           quickstart-ios/abtesting/GoogleService-Info.plist "$plist_secret"
diff --git a/.github/workflows/auth.yml b/.github/workflows/auth.yml
index fd9cce9f5be..4a0f8a36547 100644
--- a/.github/workflows/auth.yml
+++ b/.github/workflows/auth.yml
@@ -97,7 +97,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Authentication
-      setup_command: scripts/setup_quickstart_spm.sh authentication
+      setup_command: scripts/setup_quickstart.sh authentication
       plist_src_path: scripts/gha-encrypted/qs-authentication.plist.gpg
       plist_dst_path: quickstart-ios/authentication/GoogleService-Info.plist
       run_tests: false
diff --git a/.github/workflows/crashlytics.yml b/.github/workflows/crashlytics.yml
index 341da63a063..79288931bc6 100644
--- a/.github/workflows/crashlytics.yml
+++ b/.github/workflows/crashlytics.yml
@@ -48,7 +48,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Crashlytics
-      setup_command: scripts/setup_quickstart_spm.sh crashlytics
+      setup_command: scripts/setup_quickstart.sh crashlytics
       plist_src_path: scripts/gha-encrypted/qs-crashlytics.plist.gpg
       plist_dst_path: quickstart-ios/crashlytics/GoogleService-Info.plist
     secrets:
@@ -74,7 +74,7 @@ jobs:
     - name: Xcode
       run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
     - name: Setup quickstart
-      run: scripts/setup_quickstart_spm.sh crashlytics
+      run: scripts/setup_quickstart.sh crashlytics
     - name: Install Secret GoogleService-Info.plist
       run: scripts/decrypt_gha_secret.sh scripts/gha-encrypted/qs-crashlytics.plist.gpg \
           quickstart-ios/crashlytics/GoogleService-Info.plist "$plist_secret"
diff --git a/.github/workflows/database.yml b/.github/workflows/database.yml
index b75ecb9f8a3..7c99accf44b 100644
--- a/.github/workflows/database.yml
+++ b/.github/workflows/database.yml
@@ -74,7 +74,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Database
-      setup_command: scripts/setup_quickstart_spm.sh database
+      setup_command: scripts/setup_quickstart.sh database
       plist_src_path: scripts/gha-encrypted/qs-database.plist.gpg
       plist_dst_path: quickstart-ios/database/GoogleService-Info.plist
       run_tests: false
diff --git a/.github/workflows/firestore.yml b/.github/workflows/firestore.yml
index 4c3e9726425..1c93b975311 100644
--- a/.github/workflows/firestore.yml
+++ b/.github/workflows/firestore.yml
@@ -605,7 +605,7 @@ jobs:
   #   uses: ./.github/workflows/common_quickstart.yml
   #   with:
   #     product: Firestore
-  #     setup_command: scripts/setup_quickstart_spm.sh firestore
+  #     setup_command: scripts/setup_quickstart.sh firestore
   #     plist_src_path: scripts/gha-encrypted/qs-firestore.plist.gpg
   #     plist_dst_path: quickstart-ios/firestore/GoogleService-Info.plist
   #     run_tests: false
diff --git a/.github/workflows/inappmessaging.yml b/.github/workflows/inappmessaging.yml
index b7ace6a847a..c4ef6f675b9 100644
--- a/.github/workflows/inappmessaging.yml
+++ b/.github/workflows/inappmessaging.yml
@@ -76,7 +76,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: InAppMessaging
-      setup_command: scripts/setup_quickstart_spm.sh inappmessaging
+      setup_command: scripts/setup_quickstart.sh inappmessaging
       plist_src_path: scripts/gha-encrypted/qs-inappmessaging.plist.gpg
       plist_dst_path: quickstart-ios/inappmessaging/GoogleService-Info.plist
       run_tests: false
diff --git a/.github/workflows/installations.yml b/.github/workflows/installations.yml
index 6037a762d2c..140274967e2 100644
--- a/.github/workflows/installations.yml
+++ b/.github/workflows/installations.yml
@@ -53,7 +53,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Installations
-      setup_command: scripts/setup_quickstart_spm.sh installations
+      setup_command: scripts/setup_quickstart.sh installations
       plist_src_path: scripts/gha-encrypted/Installations/GoogleService-Info.plist.gpg
       plist_dst_path: quickstart-ios/installations/GoogleService-Info.plist
     secrets:
@@ -76,7 +76,7 @@ jobs:
     - name: Xcode
       run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
     - name: Setup quickstart
-      run: scripts/setup_quickstart_spm.sh installations
+      run: scripts/setup_quickstart.sh installations
     - name: Copy mock plist
       run: cp quickstart-ios/mock-GoogleService-Info.plist quickstart-ios/installations/GoogleService-Info.plist
     - name: Build quickstart
diff --git a/.github/workflows/messaging.yml b/.github/workflows/messaging.yml
index 2939d779594..86af0505687 100644
--- a/.github/workflows/messaging.yml
+++ b/.github/workflows/messaging.yml
@@ -85,7 +85,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Messaging
-      setup_command: scripts/setup_quickstart_spm.sh messaging
+      setup_command: scripts/setup_quickstart.sh messaging
       plist_src_path: scripts/gha-encrypted/qs-messaging.plist.gpg
       plist_dst_path: quickstart-ios/messaging/GoogleService-Info.plist
       run_tests: false
@@ -105,7 +105,7 @@ jobs:
     - name: Xcode
       run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
     - name: Setup quickstart
-      run: scripts/setup_quickstart_spm.sh messaging
+      run: scripts/setup_quickstart.sh messaging
     - name: Install Secret GoogleService-Info.plist
       run: scripts/decrypt_gha_secret.sh scripts/gha-encrypted/qs-messaging.plist.gpg \
           quickstart-ios/messaging/GoogleService-Info.plist "$plist_secret"
diff --git a/.github/workflows/performance.yml b/.github/workflows/performance.yml
index d5b39b13b39..2eaef8ca98e 100644
--- a/.github/workflows/performance.yml
+++ b/.github/workflows/performance.yml
@@ -82,7 +82,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Performance
-      setup_command: scripts/setup_quickstart_spm.sh performance
+      setup_command: scripts/setup_quickstart.sh performance
       plist_src_path: scripts/gha-encrypted/qs-performance.plist.gpg
       plist_dst_path: quickstart-ios/performance/GoogleService-Info.plist
     secrets:
@@ -104,7 +104,7 @@ jobs:
     - name: Install xcpretty
       run: gem install xcpretty
     - name: Setup quickstart
-      run: scripts/setup_quickstart_spm.sh performance
+      run: scripts/setup_quickstart.sh performance
     - name: Install Secret GoogleService-Info.plist
       run: scripts/decrypt_gha_secret.sh scripts/gha-encrypted/qs-performance.plist.gpg \
           quickstart-ios/performance/GoogleService-Info.plist "$plist_secret"
diff --git a/.github/workflows/prerelease.yml b/.github/workflows/prerelease.yml
index e6575f9a614..7a9537ecac6 100644
--- a/.github/workflows/prerelease.yml
+++ b/.github/workflows/prerelease.yml
@@ -101,7 +101,7 @@ jobs:
     - name: Xcode
       run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
     - name: Setup testing repo and quickstart
-      run: scripts/setup_quickstart_spm.sh ${{ matrix.product }} prerelease_testing
+      run: scripts/setup_quickstart.sh ${{ matrix.product }} prerelease_testing
     - name: Install Secret GoogleService-Info.plist
       run: |
         scripts/decrypt_gha_secret.sh \
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 0a3d4842b53..3a191c3d473 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -99,7 +99,7 @@ jobs:
     - name: Prereqs
       run: gem install xcpretty
     - name: Setup testing repo and quickstart
-      run: scripts/setup_quickstart_spm.sh ${{ matrix.product }} nightly_release_testing
+      run: scripts/setup_quickstart.sh ${{ matrix.product }} nightly_release_testing
     - name: Install Secret GoogleService-Info.plist
       run: |
         scripts/decrypt_gha_secret.sh scripts/gha-encrypted/qs-${{ matrix.product }}.plist.gpg \
diff --git a/.github/workflows/remoteconfig.yml b/.github/workflows/remoteconfig.yml
index 36ba73ed473..2293aaa9283 100644
--- a/.github/workflows/remoteconfig.yml
+++ b/.github/workflows/remoteconfig.yml
@@ -94,7 +94,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Config
-      setup_command: scripts/setup_quickstart_spm.sh config
+      setup_command: scripts/setup_quickstart.sh config
       plist_src_path: scripts/gha-encrypted/qs-config.plist.gpg
       plist_dst_path: quickstart-ios/config/GoogleService-Info.plist
     secrets:
diff --git a/.github/workflows/storage.yml b/.github/workflows/storage.yml
index 9aae03de131..8155d718928 100644
--- a/.github/workflows/storage.yml
+++ b/.github/workflows/storage.yml
@@ -83,7 +83,7 @@ jobs:
     uses: ./.github/workflows/common_quickstart.yml
     with:
       product: Storage
-      setup_command: scripts/setup_quickstart_spm.sh storage
+      setup_command: scripts/setup_quickstart.sh storage
       plist_src_path: scripts/gha-encrypted/qs-storage.plist.gpg
       plist_dst_path: quickstart-ios/storage/GoogleService-Info.plist
       run_tests: false
diff --git a/scripts/setup_quickstart.sh b/scripts/setup_quickstart.sh
index 840b1eaebdc..faf0224fec8 100755
--- a/scripts/setup_quickstart.sh
+++ b/scripts/setup_quickstart.sh
@@ -1,4 +1,6 @@
-# Copyright 2019 Google
+#!/usr/bin/env bash
+
+# Copyright 2025 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -12,63 +14,247 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Script to run in a CI `before_install` phase to setup a SPM-based
+# quickstart repo so that it can be used for integration testing.
+
+set -euo pipefail
 
-# Script to run in a CI `before_install` phase to setup the quickstart repo
-# so that it can be used for integration testing.
+# Define testing mode constants.
+readonly NIGHTLY_RELEASE_TESTING="nightly_release_testing"
+readonly PRERELEASE_TESTING="prerelease_testing"
 
-set -xeuo pipefail
+# All script logic is contained in functions. The main function is called at
+# the end.
+# Global variables:
+#   - readonly constants are defined at the top.
+#   - scripts_dir and root_dir are set after constants.
 
 scripts_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 root_dir="$(dirname "$scripts_dir")"
 
-$scripts_dir/setup_bundler.sh
+print_usage() {
+  cat <<EOF
+Usage: $(basename "$0") <sample_name> [testing_mode]
 
-# Source function to check if CI secrets are available.
-source $scripts_dir/check_secrets.sh
+This script sets up a quickstart sample for SPM integration testing.
 
-SAMPLE=$1
+ARGUMENTS:
+  <sample_name>   The name of the quickstart sample directory
+                  (e.g., "authentication").
+  [testing_mode]  Optional. Specifies the testing mode. Can be one of:
+                  - "${NIGHTLY_RELEASE_TESTING}": Points SPM to the latest
+                    CocoaPods tag.
+                  - "${PRERELEASE_TESTING}": Points SPM to the tip of the main
+                    branch.
+                  - (default): Points SPM to the current commit for PR testing.
 
-RELEASE_TESTING=${2-}
+ENVIRONMENT VARIABLES:
+  QUICKSTART_REPO: Optional. Path to a local clone of the quickstart-ios repo.
+                   If not set, the script will clone it from GitHub.
+                   Example:
+                   QUICKSTART_REPO=/path/to/quickstart-ios $(basename "$0") authentication
 
-WORKSPACE_DIR="quickstart-ios/${SAMPLE}"
-PODFILE="quickstart-ios/"$SAMPLE"/Podfile"
+  QUICKSTART_BRANCH: Optional. The branch to checkout in the quickstart repo.
+                     Defaults to the repo's default branch.
+                     Example:
+                     QUICKSTART_BRANCH=my-feature-branch $(basename "$0") authentication
 
-if [[ ! -z "${LEGACY:-}" ]]; then
-  WORKSPACE_DIR="quickstart-ios/${SAMPLE}/Legacy${SAMPLE}Quickstart"
-  PODFILE="quickstart-ios/"$SAMPLE"/Legacy${SAMPLE}Quickstart/Podfile"
-fi
+  BYPASS_SECRET_CHECK: Optional. Set to "true" to bypass the CI secret check
+                       for local runs.
+                       Example:
+                       BYPASS_SECRET_CHECK=true $(basename "$0") authentication
 
-gem install xcpretty
+  DEBUG: Optional. Set to "true" to enable shell trace mode (`set -x`).
+         Example: DEBUG=true $(basename "$0") authentication
+EOF
+}
 
-# Installations is the only quickstart that doesn't need a real
-# GoogleService-Info.plist for its tests.
-if check_secrets || [[ ${SAMPLE} == "installations" ]]; then
+# Clones or locates the quickstart repo.
+#
+# Globals:
+#   - QUICKSTART_REPO (read-only)
+# Arguments:
+#   - $1: The name of the sample.
+# Outputs:
+#   - Echoes the absolute path to the quickstart directory.
+setup_quickstart_repo() {
+  local sample_name="$1"
+  local quickstart_dir
 
-  # Specify repo so the Firebase module and header can be found in a
-  # development pod install. This is needed for the `pod install` command.
-  export FIREBASE_POD_REPO_FOR_DEV_POD=`pwd`
+  # If QUICKSTART_REPO is set, use it. Otherwise, clone the repo.
+  if [[ -n "${QUICKSTART_REPO:-}" ]]; then
+    # If the user provided a path, it must be a valid directory.
+    if [[ ! -d "${QUICKSTART_REPO}" ]]; then
+      echo "Error: QUICKSTART_REPO is set to '${QUICKSTART_REPO}'," \
+           "but this is not a valid directory." >&2
+      exit 1
+    fi
+    echo "Using local quickstart repository at ${QUICKSTART_REPO}" >&2
+    quickstart_dir="${QUICKSTART_REPO}"
+    if ! (cd "${quickstart_dir}" && \
+          git rev-parse --is-inside-work-tree >/dev/null 2>&1); then
+      echo "Error: QUICKSTART_REPO ('${quickstart_dir}') is not a git" \
+           "repository." >&2
+      exit 1
+    fi
+  else
+    # QUICKSTART_REPO is not set, so clone it.
+    quickstart_dir="quickstart-ios"
+    if [[ -d "${quickstart_dir}" ]]; then
+      echo "Quickstart repository already exists at ${quickstart_dir}" >&2
+    else
+      echo "Cloning quickstart repository into '${quickstart_dir}' directory..." >&2
+      # Do a partial, sparse clone to speed up CI. See
+      # https://github.blog/2020-12-21-get-up-to-speed-with-partial-clone-and-shallow-clone/
+      git clone --filter=blob:none --sparse \
+        https://github.com/firebase/quickstart-ios.git "${quickstart_dir}"
+    fi
+    (
+      cd "${quickstart_dir}"
+      echo "Ensuring sparse checkout is set for ${sample_name}..." >&2
+      # Checkout the sample and scripts directories.
+      git sparse-checkout set "${sample_name}" scripts shared
+    )
+  fi
 
-  git clone https://github.com/firebase/quickstart-ios.git
+  # If a branch is specified, check it out.
+  if [[ -n "${QUICKSTART_BRANCH:-}" ]]; then
+    echo "Checking out quickstart branch: ${QUICKSTART_BRANCH}" >&2
+    (
+      cd "${quickstart_dir}"
+      git fetch --quiet
+      git checkout --quiet "${QUICKSTART_BRANCH}"
+    )
+  fi
 
-  $scripts_dir/localize_podfile.swift "$WORKSPACE_DIR"/Podfile "$RELEASE_TESTING"
-  if [ "$RELEASE_TESTING" == "nightly_release_testing" ]; then
-    set +x
-    sed -i "" '1i\'$'\n'"source 'https://github.com/Firebase/SpecsReleasing.git'"$'\n' "$PODFILE"
-    set -x
-    echo "Source of Podfile for nightly release testing is updated."
+  # Return the absolute path to the quickstart directory.
+  (cd "$quickstart_dir" && pwd)
+}
+
+# Updates the SPM dependency in the Xcode project based on the testing mode.
+#
+# Globals:
+#   - NIGHTLY_RELEASE_TESTING (read-only)
+#   - PRERELEASE_TESTING (read-only)
+#   - scripts_dir (read-only)
+#   - root_dir (read-only)
+# Arguments:
+#   - $1: The testing mode.
+#   - $2: The absolute path to the .xcodeproj file.
+update_spm_dependency() {
+  local release_testing_mode="$1"
+  local absolute_project_file="$2"
+
+  case "$release_testing_mode" in
+    "${NIGHTLY_RELEASE_TESTING}")
+      # For release testing, find the latest CocoaPods tag.
+      local latest_tag
+      latest_tag=$(git -C "$root_dir" tag -l "CocoaPods-*" --sort=-v:refname |
+        awk '/^CocoaPods-[0-9]+\.[0-9]+\.[0-9]+$/{print; exit}')
+      if [[ -z "$latest_tag" ]]; then
+        echo "Error: Could not find the latest CocoaPods tag." >&2
+        echo "This is often caused by a shallow git clone in a CI environment." >&2
+        echo "If you are running in GitHub Actions, please ensure your checkout" >&2
+        echo "step includes 'fetch-depth: 0' to fetch the full git history." >&2
+        exit 1
+      fi
+      local tag_revision
+      tag_revision=$(git -C "$root_dir" rev-list -n 1 "$latest_tag")
+      echo "Setting SPM dependency to revision for tag ${latest_tag}:" \
+           "${tag_revision}"
+      "$scripts_dir/update_firebase_spm_dependency.sh" \
+        "$absolute_project_file" --revision "$tag_revision"
+      ;;
+
+    "${PRERELEASE_TESTING}")
+      # For prerelease testing, point to the tip of the main branch.
+      echo "Setting SPM dependency to the tip of the main branch."
+      "$scripts_dir/update_firebase_spm_dependency.sh" \
+        "$absolute_project_file" --prerelease
+      ;;
+
+    *)
+      # For PR testing, point to the current commit.
+      local current_revision
+      current_revision=$(git -C "$root_dir" rev-parse HEAD)
+      echo "Setting SPM dependency to current revision: ${current_revision}"
+      "$scripts_dir/update_firebase_spm_dependency.sh" \
+        "$absolute_project_file" --revision "$current_revision"
+      ;;
+  esac
+}
+
+main() {
+  # --- Argument Parsing ---
+  if [[ -z "${1:-}" ]]; then
+    print_usage
+    exit 1
   fi
-  if [ "$RELEASE_TESTING" == "prerelease_testing" ]; then
-    set +x
-    sed -i "" '1i\'$'\n'"source 'https://github.com/Firebase/SpecsTesting.git'"$'\n' "$PODFILE"
+
+  local sample="$1"
+  local release_testing="${2-}"
+
+  # Validate release_testing argument.
+  case "$release_testing" in
+    "" | "${NIGHTLY_RELEASE_TESTING}" | "${PRERELEASE_TESTING}")
+      # This is a valid value (or empty), so do nothing.
+      ;;
+    *)
+      # This is an invalid value.
+      echo "Error: Invalid testing_mode: '${release_testing}'" >&2
+      print_usage
+      exit 1
+      ;;
+  esac
+
+  # --- Environment Setup and Validation ---
+  # Enable trace mode if DEBUG is set to 'true'
+  if [[ "${DEBUG:-false}" == "true" ]]; then
     set -x
-    echo "Source of Podfile for prerelease testing is updated."
   fi
-  cd "${WORKSPACE_DIR}"
 
-  # To test a branch, uncomment the following line
-  # git checkout {BRANCH_NAME}
+  # Source function to check if CI secrets are available.
+  source "$scripts_dir/check_secrets.sh"
+
+  # Some quickstarts may not need a real GoogleService-Info.plist for their
+  # tests. When QUICKSTART_REPO is set (for local runs) or BYPASS_SECRET_CHECK
+  # is true, the secrets check is skipped.
+  if [[ -z "${QUICKSTART_REPO:-}" ]] && \
+     [[ "${BYPASS_SECRET_CHECK:-}" != "true" ]] && \
+     ! check_secrets && \
+     [[ "${sample}" != "installations" ]]; then
+    echo "Skipping quickstart setup: CI secrets are not available."
+    exit 0
+  fi
+
+  # --- Main Logic ---
+  local quickstart_dir
+  quickstart_dir=$(setup_quickstart_repo "$sample")
+
+  local quickstart_project_dir="${quickstart_dir}/${sample}"
+
+  if [[ ! -d "${quickstart_project_dir}" ]]; then
+    echo "Error: Sample directory not found at '${quickstart_project_dir}'" >&2
+    exit 1
+  fi
+
+  # Find the .xcodeproj file within the sample directory.
+  # Fail if there isn't exactly one.
+  # Enable nullglob to ensure the glob expands to an empty list if no files
+  # are found.
+  shopt -s nullglob
+  local project_files=("${quickstart_project_dir}"/*.xcodeproj)
+  # Restore default globbing behavior.
+  shopt -u nullglob
+  if [[ "${#project_files[@]}" -ne 1 ]]; then
+    echo "Error: Expected 1 .xcodeproj file in" \
+         "'${quickstart_project_dir}', but found ${#project_files[@]}." >&2
+    exit 1
+  fi
+  local project_file="${project_files[0]}"
+
+  update_spm_dependency "$release_testing" "$project_file"
+}
 
-  bundle update --bundler
-  bundle install
-  pod update
-fi
+# Run the main function with all provided arguments.
+main "$@"
diff --git a/scripts/setup_quickstart_spm.sh b/scripts/setup_quickstart_spm.sh
deleted file mode 100755
index faf0224fec8..00000000000
--- a/scripts/setup_quickstart_spm.sh
+++ /dev/null
@@ -1,260 +0,0 @@
-#!/usr/bin/env bash
-
-# Copyright 2025 Google LLC
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# Script to run in a CI `before_install` phase to setup a SPM-based
-# quickstart repo so that it can be used for integration testing.
-
-set -euo pipefail
-
-# Define testing mode constants.
-readonly NIGHTLY_RELEASE_TESTING="nightly_release_testing"
-readonly PRERELEASE_TESTING="prerelease_testing"
-
-# All script logic is contained in functions. The main function is called at
-# the end.
-# Global variables:
-#   - readonly constants are defined at the top.
-#   - scripts_dir and root_dir are set after constants.
-
-scripts_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-root_dir="$(dirname "$scripts_dir")"
-
-print_usage() {
-  cat <<EOF
-Usage: $(basename "$0") <sample_name> [testing_mode]
-
-This script sets up a quickstart sample for SPM integration testing.
-
-ARGUMENTS:
-  <sample_name>   The name of the quickstart sample directory
-                  (e.g., "authentication").
-  [testing_mode]  Optional. Specifies the testing mode. Can be one of:
-                  - "${NIGHTLY_RELEASE_TESTING}": Points SPM to the latest
-                    CocoaPods tag.
-                  - "${PRERELEASE_TESTING}": Points SPM to the tip of the main
-                    branch.
-                  - (default): Points SPM to the current commit for PR testing.
-
-ENVIRONMENT VARIABLES:
-  QUICKSTART_REPO: Optional. Path to a local clone of the quickstart-ios repo.
-                   If not set, the script will clone it from GitHub.
-                   Example:
-                   QUICKSTART_REPO=/path/to/quickstart-ios $(basename "$0") authentication
-
-  QUICKSTART_BRANCH: Optional. The branch to checkout in the quickstart repo.
-                     Defaults to the repo's default branch.
-                     Example:
-                     QUICKSTART_BRANCH=my-feature-branch $(basename "$0") authentication
-
-  BYPASS_SECRET_CHECK: Optional. Set to "true" to bypass the CI secret check
-                       for local runs.
-                       Example:
-                       BYPASS_SECRET_CHECK=true $(basename "$0") authentication
-
-  DEBUG: Optional. Set to "true" to enable shell trace mode (`set -x`).
-         Example: DEBUG=true $(basename "$0") authentication
-EOF
-}
-
-# Clones or locates the quickstart repo.
-#
-# Globals:
-#   - QUICKSTART_REPO (read-only)
-# Arguments:
-#   - $1: The name of the sample.
-# Outputs:
-#   - Echoes the absolute path to the quickstart directory.
-setup_quickstart_repo() {
-  local sample_name="$1"
-  local quickstart_dir
-
-  # If QUICKSTART_REPO is set, use it. Otherwise, clone the repo.
-  if [[ -n "${QUICKSTART_REPO:-}" ]]; then
-    # If the user provided a path, it must be a valid directory.
-    if [[ ! -d "${QUICKSTART_REPO}" ]]; then
-      echo "Error: QUICKSTART_REPO is set to '${QUICKSTART_REPO}'," \
-           "but this is not a valid directory." >&2
-      exit 1
-    fi
-    echo "Using local quickstart repository at ${QUICKSTART_REPO}" >&2
-    quickstart_dir="${QUICKSTART_REPO}"
-    if ! (cd "${quickstart_dir}" && \
-          git rev-parse --is-inside-work-tree >/dev/null 2>&1); then
-      echo "Error: QUICKSTART_REPO ('${quickstart_dir}') is not a git" \
-           "repository." >&2
-      exit 1
-    fi
-  else
-    # QUICKSTART_REPO is not set, so clone it.
-    quickstart_dir="quickstart-ios"
-    if [[ -d "${quickstart_dir}" ]]; then
-      echo "Quickstart repository already exists at ${quickstart_dir}" >&2
-    else
-      echo "Cloning quickstart repository into '${quickstart_dir}' directory..." >&2
-      # Do a partial, sparse clone to speed up CI. See
-      # https://github.blog/2020-12-21-get-up-to-speed-with-partial-clone-and-shallow-clone/
-      git clone --filter=blob:none --sparse \
-        https://github.com/firebase/quickstart-ios.git "${quickstart_dir}"
-    fi
-    (
-      cd "${quickstart_dir}"
-      echo "Ensuring sparse checkout is set for ${sample_name}..." >&2
-      # Checkout the sample and scripts directories.
-      git sparse-checkout set "${sample_name}" scripts shared
-    )
-  fi
-
-  # If a branch is specified, check it out.
-  if [[ -n "${QUICKSTART_BRANCH:-}" ]]; then
-    echo "Checking out quickstart branch: ${QUICKSTART_BRANCH}" >&2
-    (
-      cd "${quickstart_dir}"
-      git fetch --quiet
-      git checkout --quiet "${QUICKSTART_BRANCH}"
-    )
-  fi
-
-  # Return the absolute path to the quickstart directory.
-  (cd "$quickstart_dir" && pwd)
-}
-
-# Updates the SPM dependency in the Xcode project based on the testing mode.
-#
-# Globals:
-#   - NIGHTLY_RELEASE_TESTING (read-only)
-#   - PRERELEASE_TESTING (read-only)
-#   - scripts_dir (read-only)
-#   - root_dir (read-only)
-# Arguments:
-#   - $1: The testing mode.
-#   - $2: The absolute path to the .xcodeproj file.
-update_spm_dependency() {
-  local release_testing_mode="$1"
-  local absolute_project_file="$2"
-
-  case "$release_testing_mode" in
-    "${NIGHTLY_RELEASE_TESTING}")
-      # For release testing, find the latest CocoaPods tag.
-      local latest_tag
-      latest_tag=$(git -C "$root_dir" tag -l "CocoaPods-*" --sort=-v:refname |
-        awk '/^CocoaPods-[0-9]+\.[0-9]+\.[0-9]+$/{print; exit}')
-      if [[ -z "$latest_tag" ]]; then
-        echo "Error: Could not find the latest CocoaPods tag." >&2
-        echo "This is often caused by a shallow git clone in a CI environment." >&2
-        echo "If you are running in GitHub Actions, please ensure your checkout" >&2
-        echo "step includes 'fetch-depth: 0' to fetch the full git history." >&2
-        exit 1
-      fi
-      local tag_revision
-      tag_revision=$(git -C "$root_dir" rev-list -n 1 "$latest_tag")
-      echo "Setting SPM dependency to revision for tag ${latest_tag}:" \
-           "${tag_revision}"
-      "$scripts_dir/update_firebase_spm_dependency.sh" \
-        "$absolute_project_file" --revision "$tag_revision"
-      ;;
-
-    "${PRERELEASE_TESTING}")
-      # For prerelease testing, point to the tip of the main branch.
-      echo "Setting SPM dependency to the tip of the main branch."
-      "$scripts_dir/update_firebase_spm_dependency.sh" \
-        "$absolute_project_file" --prerelease
-      ;;
-
-    *)
-      # For PR testing, point to the current commit.
-      local current_revision
-      current_revision=$(git -C "$root_dir" rev-parse HEAD)
-      echo "Setting SPM dependency to current revision: ${current_revision}"
-      "$scripts_dir/update_firebase_spm_dependency.sh" \
-        "$absolute_project_file" --revision "$current_revision"
-      ;;
-  esac
-}
-
-main() {
-  # --- Argument Parsing ---
-  if [[ -z "${1:-}" ]]; then
-    print_usage
-    exit 1
-  fi
-
-  local sample="$1"
-  local release_testing="${2-}"
-
-  # Validate release_testing argument.
-  case "$release_testing" in
-    "" | "${NIGHTLY_RELEASE_TESTING}" | "${PRERELEASE_TESTING}")
-      # This is a valid value (or empty), so do nothing.
-      ;;
-    *)
-      # This is an invalid value.
-      echo "Error: Invalid testing_mode: '${release_testing}'" >&2
-      print_usage
-      exit 1
-      ;;
-  esac
-
-  # --- Environment Setup and Validation ---
-  # Enable trace mode if DEBUG is set to 'true'
-  if [[ "${DEBUG:-false}" == "true" ]]; then
-    set -x
-  fi
-
-  # Source function to check if CI secrets are available.
-  source "$scripts_dir/check_secrets.sh"
-
-  # Some quickstarts may not need a real GoogleService-Info.plist for their
-  # tests. When QUICKSTART_REPO is set (for local runs) or BYPASS_SECRET_CHECK
-  # is true, the secrets check is skipped.
-  if [[ -z "${QUICKSTART_REPO:-}" ]] && \
-     [[ "${BYPASS_SECRET_CHECK:-}" != "true" ]] && \
-     ! check_secrets && \
-     [[ "${sample}" != "installations" ]]; then
-    echo "Skipping quickstart setup: CI secrets are not available."
-    exit 0
-  fi
-
-  # --- Main Logic ---
-  local quickstart_dir
-  quickstart_dir=$(setup_quickstart_repo "$sample")
-
-  local quickstart_project_dir="${quickstart_dir}/${sample}"
-
-  if [[ ! -d "${quickstart_project_dir}" ]]; then
-    echo "Error: Sample directory not found at '${quickstart_project_dir}'" >&2
-    exit 1
-  fi
-
-  # Find the .xcodeproj file within the sample directory.
-  # Fail if there isn't exactly one.
-  # Enable nullglob to ensure the glob expands to an empty list if no files
-  # are found.
-  shopt -s nullglob
-  local project_files=("${quickstart_project_dir}"/*.xcodeproj)
-  # Restore default globbing behavior.
-  shopt -u nullglob
-  if [[ "${#project_files[@]}" -ne 1 ]]; then
-    echo "Error: Expected 1 .xcodeproj file in" \
-         "'${quickstart_project_dir}', but found ${#project_files[@]}." >&2
-    exit 1
-  fi
-  local project_file="${project_files[0]}"
-
-  update_spm_dependency "$release_testing" "$project_file"
-}
-
-# Run the main function with all provided arguments.
-main "$@"