diff --git a/.github/workflows/callable-test-core-build-process.yml b/.github/workflows/callable-test-core-build-process.yml
new file mode 100644
index 0000000000000..00024a94bf223
--- /dev/null
+++ b/.github/workflows/callable-test-core-build-process.yml
@@ -0,0 +1,73 @@
+##
+# A callable workflow that tests the WordPress Core build process.
+##
+name: Test the WordPress Build Process
+
+on:
+  workflow_call:
+    inputs:
+      os:
+        description: 'Operating system to run tests on'
+        required: false
+        type: 'string'
+        default: 'ubuntu-latest'
+      directory:
+        description: 'Directory to run WordPress out of. Valid values are src or build'
+        required: false
+        type: 'string'
+        default: 'src'
+
+env:
+  PUPPETEER_SKIP_DOWNLOAD: ${{ true }}
+
+jobs:
+  # Verifies that installing npm dependencies and building WordPress works as expected.
+  #
+  # Performs the following steps:
+  # - Checks out the repository.
+  # - Sets up Node.js.
+  # - Logs debug information about the GitHub Action runner.
+  # - Installs npm dependencies.
+  # - Builds WordPress to run from the desired location (src or build).
+  # - Ensures version-controlled files are not modified or deleted.
+  # - Cleans up after building WordPress.
+  # - Ensures version-controlled files are not modified or deleted.
+  build-process-tests:
+    name: Core running from ${{ inputs.directory }} / ${{ inputs.os == 'macos-latest' && 'MacOS' || inputs.os == 'windows-latest' && 'Windows' || 'Linux' }}
+    runs-on: ${{ inputs.os }}
+    timeout-minutes: 20
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4.0.0
+        with:
+          show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
+
+      - name: Set up Node.js
+        uses: actions/setup-node@5e21ff4d9bc1a8cf6de233a3057d20ec6b3fb69d # v3.8.1
+        with:
+          node-version-file: '.nvmrc'
+          cache: npm
+
+      - name: Log debug information
+        run: |
+          npm --version
+          node --version
+          curl --version
+          git --version
+          svn --version
+
+      - name: Install npm Dependencies
+        run: npm ci
+
+      - name: Build WordPress to run from ${{ inputs.directory }}
+        run: npm run build${{ inputs.directory == 'src' && ':dev' || '' }}
+
+      - name: Ensure version-controlled files are not modified or deleted during building
+        run: git diff --exit-code
+
+      - name: Clean after building to run from ${{ inputs.directory }}
+        run: npm run grunt clean${{ inputs.directory == 'src' && ' -- --dev' || '' }}
+
+      - name: Ensure version-controlled files are not modified or deleted during cleaning
+        run: git diff --exit-code
diff --git a/.github/workflows/callable-test-gutenberg-build-process.yml b/.github/workflows/callable-test-gutenberg-build-process.yml
new file mode 100644
index 0000000000000..5a2fdda0c15f2
--- /dev/null
+++ b/.github/workflows/callable-test-gutenberg-build-process.yml
@@ -0,0 +1,92 @@
+##
+# A callable workflow that tests the Gutenberg plugin build process.
+##
+name: Test the Gutenberg plugin Build Process
+
+on:
+  workflow_call:
+    inputs:
+      os:
+        description: 'Operating system to run tests on'
+        required: false
+        type: 'string'
+        default: 'ubuntu-latest'
+      directory:
+        description: 'Directory to run WordPress out of. Valid values are src or build'
+        required: false
+        type: 'string'
+        default: 'src'
+
+env:
+  GUTENBERG_DIRECTORY: ${{ inputs.directory == 'build' && 'build' || 'src' }}/wp-content/plugins/gutenberg
+  PUPPETEER_SKIP_DOWNLOAD: ${{ true }}
+
+jobs:
+  # Verifies that installing npm dependencies and building the Gutenberg plugin works as expected.
+  #
+  # Performs the following steps:
+  # - Checks out the repository.
+  # - Checks out the Gutenberg plugin repository in the plugins directory.
+  # - Sets up Node.js.
+  # - Logs debug information about the GitHub Action runner.
+  # - Installs Core npm dependencies.
+  # - Installs npm dependencies for Gutenberg.
+  # - Runs the Gutenberg build process.
+  # - Builds WordPress to run from the relevant location (src or build).
+  # - Runs the Gutenberg build process.
+  # - Ensures version-controlled files are not modified or deleted.
+  build-process-tests:
+    name: Gutenberg running from ${{ inputs.directory }} / ${{ inputs.os == 'macos-latest' && 'MacOS' || inputs.os == 'windows-latest' && 'Windows' || 'Linux' }}
+    runs-on: ${{ inputs.os }}
+    timeout-minutes: 30
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4.0.0
+        with:
+          show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
+
+      - name: Checkout Gutenberg plugin
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4.0.0
+        with:
+          repository: 'WordPress/gutenberg'
+          path: ${{ env.GUTENBERG_DIRECTORY }}
+          show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
+
+      - name: Set up Node.js
+        uses: actions/setup-node@5e21ff4d9bc1a8cf6de233a3057d20ec6b3fb69d # v3.8.1
+        with:
+          node-version-file: '.nvmrc'
+          cache: npm
+          cache-dependency-path: |
+            package-lock.json
+            ${{ env.GUTENBERG_DIRECTORY }}/package-lock.json
+
+      - name: Log debug information
+        run: |
+          npm --version
+          node --version
+          curl --version
+          git --version
+          svn --version
+
+      - name: Install Core Dependencies
+        run: npm ci
+
+      - name: Install Gutenberg Dependencies
+        run: npm ci
+        working-directory: ${{ env.GUTENBERG_DIRECTORY }}
+
+      - name: Run Gutenberg build script
+        run: npm run build
+        working-directory: ${{ env.GUTENBERG_DIRECTORY }}
+
+      - name: Build WordPress to run from ${{ inputs.directory }}
+        run: npm run build${{ inputs.directory == 'src' && ':dev' || '' }}
+
+      - name: Run Gutenberg build script after building Core to run from ${{ inputs.directory }}
+        run: npm run build
+        working-directory: ${{ env.GUTENBERG_DIRECTORY }}
+
+      - name: Ensure version-controlled files are not modified or deleted during building
+        run: git diff --exit-code
diff --git a/.github/workflows/test-build-processes.yml b/.github/workflows/test-build-processes.yml
new file mode 100644
index 0000000000000..b1ff0e25b8379
--- /dev/null
+++ b/.github/workflows/test-build-processes.yml
@@ -0,0 +1,166 @@
+name: Test Build Processes
+
+on:
+  push:
+    branches:
+      - trunk
+      - '3.[7-9]'
+      - '[4-9].[0-9]'
+    tags:
+      - '[0-9]+.[0-9]'
+      - '[0-9]+.[0-9].[0-9]+'
+  pull_request:
+    branches:
+      - trunk
+      - '3.[7-9]'
+      - '[4-9].[0-9]'
+    paths:
+      # These files configure npm. Changes could affect the outcome.
+      - 'package*.json'
+      # JavaScript files are built using npm.
+      - '**.js'
+      # CSS and SCSS files are built using npm.
+      - '**.scss'
+      - '**.css'
+      # Changes to workflow files should always verify all workflows are successful.
+      - '.github/workflows/**.yml'
+  workflow_dispatch:
+
+# Cancels all previous workflow runs for pull requests that have not completed.
+concurrency:
+  # The concurrency group contains the workflow name and the branch name for pull requests
+  # or the commit hash for any other events.
+  group: ${{ github.workflow }}-${{ github.event_name == 'pull_request' && github.head_ref || github.sha }}
+  cancel-in-progress: true
+
+# Disable permissions for all available scopes by default.
+# Any needed permissions should be configured at the job level.
+permissions: {}
+
+jobs:
+  # Creates a job to test the WordPress Core build process on multiple operating systems.
+  test-core-build-process:
+    name: Core running from ${{ matrix.directory }}
+    uses: desrosj/wordpress-develop/.github/workflows/callable-test-core-build-process.yml@combine/npm-testing
+    permissions:
+      contents: read
+    if: ${{ github.repository == 'WordPress/wordpress-develop' || github.event_name == 'pull_request' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, windows-latest ]
+        directory: [ 'src', 'build' ]
+    with:
+      os: ${{ matrix.os }}
+      directory: ${{ matrix.directory }}
+
+  # Creates a job to test the WordPress Core build process on MacOS.
+  #
+  # This is separate from the job above in order to use stricter conditions about when to run.
+  # This avoids unintentionally consuming excessive minutes, as MacOS jobs consume minutes at a 10x rate.
+  #
+  # The `matrix` and `runner` contexts are not available for use within `if` expressions. So there is
+  # currently no way to determine the OS being used on a given job.
+  # See https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability.
+  test-core-build-process-macos:
+    name: Core running from ${{ matrix.directory }}
+    uses: desrosj/wordpress-develop/.github/workflows/callable-test-core-build-process.yml@combine/npm-testing
+    permissions:
+      contents: read
+    if: ${{ github.repository == 'WordPress/wordpress-develop' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ macos-latest ]
+        directory: [ 'src', 'build' ]
+    with:
+      os: ${{ matrix.os }}
+      directory: ${{ matrix.directory }}
+
+  # Creates a job to test the Gutenberg plugin build process on multiple operating systems.
+  test-gutenberg-build-process:
+    name: Gutenberg running from ${{ matrix.directory }}
+    uses: desrosj/wordpress-develop/.github/workflows/callable-test-gutenberg-build-process.yml@combine/npm-testing
+    permissions:
+      contents: read
+    if: ${{ github.repository == 'WordPress/wordpress-develop' || github.event_name == 'pull_request' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, windows-latest ]
+        directory: [ 'src', 'build' ]
+    with:
+      os: ${{ matrix.os }}
+      directory: ${{ matrix.directory }}
+
+  # Creates a job to test the Gutenberg plugin build process on MacOS.
+  #
+  # This is separate from the job above in order to use stricter conditions about when to run.
+  # This avoids unintentionally consuming excessive minutes, as MacOS jobs consume minutes at a 10x rate.
+  #
+  # The `matrix` and `runner` contexts are not available for use within `if` expressions. So there is
+  # currently no way to determine the OS being used on a given job.
+  # See https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability.
+  test-gutenberg-build-process-macos:
+    name: Gutenberg running from ${{ matrix.directory }}
+    uses: desrosj/wordpress-develop/.github/workflows/callable-test-gutenberg-build-process.yml@combine/npm-testing
+    permissions:
+      contents: read
+    if: ${{ github.repository == 'WordPress/wordpress-develop' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ macos-latest ]
+        directory: [ 'src', 'build' ]
+    with:
+      os: ${{ matrix.os }}
+      directory: ${{ matrix.directory }}
+
+  slack-notifications:
+    name: Slack Notifications
+    uses: WordPress/wordpress-develop/.github/workflows/slack-notifications.yml@trunk
+    permissions:
+      actions: read
+      contents: read
+    needs: [ test-core-build-process, test-core-build-process-macos, test-gutenberg-build-process, test-gutenberg-build-process-macos ]
+    if: ${{ github.repository == 'WordPress/wordpress-develop' && github.event_name != 'pull_request' && always() }}
+    with:
+      calling_status: ${{ contains( needs.*.result, 'cancelled' ) && 'cancelled' || contains( needs.*.result, 'failure' ) && 'failure' || 'success' }}
+    secrets:
+      SLACK_GHA_SUCCESS_WEBHOOK: ${{ secrets.SLACK_GHA_SUCCESS_WEBHOOK }}
+      SLACK_GHA_CANCELLED_WEBHOOK: ${{ secrets.SLACK_GHA_CANCELLED_WEBHOOK }}
+      SLACK_GHA_FIXED_WEBHOOK: ${{ secrets.SLACK_GHA_FIXED_WEBHOOK }}
+      SLACK_GHA_FAILURE_WEBHOOK: ${{ secrets.SLACK_GHA_FAILURE_WEBHOOK }}
+
+  failed-workflow:
+    name: Failed workflow tasks
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+    needs: [ slack-notifications ]
+    if: |
+      always() &&
+      github.repository == 'WordPress/wordpress-develop' &&
+      github.event_name != 'pull_request' &&
+      github.run_attempt < 2 &&
+      (
+        contains( needs.*.result, 'cancelled' ) ||
+        contains( needs.*.result, 'failure' )
+      )
+
+    steps:
+      - name: Dispatch workflow run
+        uses: actions/github-script@d7906e4ad0b1822421a7e6a35d5ca353c962f410 # v6.4.1
+        with:
+          retries: 2
+          retry-exempt-status-codes: 418
+          script: |
+            github.rest.actions.createWorkflowDispatch({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              workflow_id: 'failed-workflow.yml',
+              ref: 'trunk',
+              inputs: {
+                run_id: '${{ github.run_id }}'
+              }
+            });
diff --git a/.github/workflows/test-npm.yml b/.github/workflows/test-npm.yml
deleted file mode 100644
index d53c8ec825690..0000000000000
--- a/.github/workflows/test-npm.yml
+++ /dev/null
@@ -1,225 +0,0 @@
-name: Test npm
-
-on:
-  push:
-    branches:
-      - trunk
-      - '3.[7-9]'
-      - '[4-9].[0-9]'
-    tags:
-      - '[0-9]+.[0-9]'
-      - '[0-9]+.[0-9].[0-9]+'
-  pull_request:
-    branches:
-      - trunk
-      - '3.[7-9]'
-      - '[4-9].[0-9]'
-    paths:
-      # These files configure npm. Changes could affect the outcome.
-      - 'package*.json'
-      # JavaScript files are built using npm.
-      - '**.js'
-      # CSS and SCSS files are built using npm.
-      - '**.scss'
-      - '**.css'
-      # Changes to workflow files should always verify all workflows are successful.
-      - '.github/workflows/**.yml'
-  workflow_dispatch:
-
-# Cancels all previous workflow runs for pull requests that have not completed.
-concurrency:
-  # The concurrency group contains the workflow name and the branch name for pull requests
-  # or the commit hash for any other events.
-  group: ${{ github.workflow }}-${{ github.event_name == 'pull_request' && github.head_ref || github.sha }}
-  cancel-in-progress: true
-
-# Disable permissions for all available scopes by default.
-# Any needed permissions should be configured at the job level.
-permissions: {}
-
-env:
-  PUPPETEER_SKIP_DOWNLOAD: ${{ true }}
-
-jobs:
-  # Verifies that installing npm dependencies and building WordPress works as expected.
-  #
-  # Performs the following steps:
-  # - Checks out the repository.
-  # - Sets up Node.js.
-  # - Logs debug information about the GitHub Action runner.
-  # - Installs npm dependencies.
-  # - Builds WordPress to run from the `build` directory.
-  # - Cleans up after building WordPress to the `build` directory.
-  # - Ensures version-controlled files are not modified or deleted.
-  # - Builds WordPress to run from the `src` directory.
-  # - Cleans up after building WordPress to the `src` directory.
-  # - Ensures version-controlled files are not modified or deleted.
-  test-npm:
-    name: Test npm on ${{ matrix.os }}
-    runs-on: ${{ matrix.os }}
-    permissions:
-      contents: read
-    timeout-minutes: 20
-    if: ${{ github.repository == 'WordPress/wordpress-develop' || github.event_name == 'pull_request' }}
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ ubuntu-latest, windows-latest ]
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4.0.0
-        with:
-          show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
-
-      - name: Set up Node.js
-        uses: actions/setup-node@5e21ff4d9bc1a8cf6de233a3057d20ec6b3fb69d # v3.8.1
-        with:
-          node-version-file: '.nvmrc'
-          cache: npm
-
-      - name: Log debug information
-        run: |
-          npm --version
-          node --version
-          curl --version
-          git --version
-          svn --version
-
-      - name: Install npm Dependencies
-        run: npm ci
-
-      - name: Build WordPress in /src
-        run: npm run build:dev
-
-      - name: Clean after building in /src
-        run: npm run grunt clean -- --dev
-
-      - name: Ensure version-controlled files are not modified or deleted during building and cleaning
-        run: git diff --exit-code
-
-      - name: Build WordPress
-        run: npm run build
-
-      - name: Clean after building
-        run: npm run grunt clean
-
-      - name: Ensure version-controlled files are not modified or deleted during building and cleaning
-        run: git diff --exit-code
-
-  # Verifies that installing npm dependencies and building WordPress works as expected on MacOS.
-  #
-  # This is separate from the job above in order to use stricter conditions about when to run.
-  # This avoids unintentionally consuming excessive minutes, as MacOS jobs consume minutes at a 10x rate.
-  #
-  # The `matrix` and `runner` contexts are not available for use within `if` expressions. So there is
-  # currently no way to determine the OS being used on a given job.
-  # See https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability.
-  #
-  # Performs the following steps:
-  # - Checks out the repository.
-  # - Sets up Node.js.
-  # - Logs debug information about the GitHub Action runner.
-  # - Installs npm dependencies.
-  # - Builds WordPress to run from the `build` directory.
-  # - Cleans up after building WordPress to the `build` directory.
-  # - Ensures version-controlled files are not modified or deleted.
-  # - Builds WordPress to run from the `src` directory.
-  # - Cleans up after building WordPress to the `src` directory.
-  # - Ensures version-controlled files are not modified or deleted.
-  test-npm-macos:
-    name: Test npm on MacOS
-    runs-on: macos-latest
-    permissions:
-      contents: read
-    timeout-minutes: 30
-    if: ${{ github.repository == 'WordPress/wordpress-develop' }}
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4.0.0
-        with:
-          show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
-
-      - name: Set up Node.js
-        uses: actions/setup-node@5e21ff4d9bc1a8cf6de233a3057d20ec6b3fb69d # v3.8.1
-        with:
-          node-version-file: '.nvmrc'
-          cache: npm
-
-      - name: Log debug information
-        run: |
-          npm --version
-          node --version
-          curl --version
-          git --version
-          svn --version
-
-      - name: Install npm Dependencies
-        run: npm ci
-
-      - name: Build WordPress in /src
-        run: npm run build:dev
-
-      - name: Clean after building in /src
-        run: npm run grunt clean -- --dev
-
-      - name: Ensure version-controlled files are not modified or deleted during building and cleaning
-        run: git diff --exit-code
-
-      - name: Build WordPress
-        run: npm run build
-
-      - name: Clean after building
-        run: npm run grunt clean
-
-      - name: Ensure version-controlled files are not modified or deleted during building and cleaning
-        run: git diff --exit-code
-
-  slack-notifications:
-    name: Slack Notifications
-    uses: WordPress/wordpress-develop/.github/workflows/slack-notifications.yml@trunk
-    permissions:
-      actions: read
-      contents: read
-    needs: [ test-npm, test-npm-macos ]
-    if: ${{ github.repository == 'WordPress/wordpress-develop' && github.event_name != 'pull_request' && always() }}
-    with:
-      calling_status: ${{ contains( needs.*.result, 'cancelled' ) && 'cancelled' || contains( needs.*.result, 'failure' ) && 'failure' || 'success' }}
-    secrets:
-      SLACK_GHA_SUCCESS_WEBHOOK: ${{ secrets.SLACK_GHA_SUCCESS_WEBHOOK }}
-      SLACK_GHA_CANCELLED_WEBHOOK: ${{ secrets.SLACK_GHA_CANCELLED_WEBHOOK }}
-      SLACK_GHA_FIXED_WEBHOOK: ${{ secrets.SLACK_GHA_FIXED_WEBHOOK }}
-      SLACK_GHA_FAILURE_WEBHOOK: ${{ secrets.SLACK_GHA_FAILURE_WEBHOOK }}
-
-  failed-workflow:
-    name: Failed workflow tasks
-    runs-on: ubuntu-latest
-    permissions:
-      actions: write
-    needs: [ slack-notifications ]
-    if: |
-      always() &&
-      github.repository == 'WordPress/wordpress-develop' &&
-      github.event_name != 'pull_request' &&
-      github.run_attempt < 2 &&
-      (
-        contains( needs.*.result, 'cancelled' ) ||
-        contains( needs.*.result, 'failure' )
-      )
-
-    steps:
-      - name: Dispatch workflow run
-        uses: actions/github-script@d7906e4ad0b1822421a7e6a35d5ca353c962f410 # v6.4.1
-        with:
-          retries: 2
-          retry-exempt-status-codes: 418
-          script: |
-            github.rest.actions.createWorkflowDispatch({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              workflow_id: 'failed-workflow.yml',
-              ref: 'trunk',
-              inputs: {
-                run_id: '${{ github.run_id }}'
-              }
-            });