diff --git a/.env b/.env
index ace9464317..2309631a5e 100644
--- a/.env
+++ b/.env
@@ -45,17 +45,21 @@ LOCAL_PHP_XDEBUG=false
 # Whether or not to enable Memcached.
 LOCAL_PHP_MEMCACHED=false
 
+##
 # The database software to use.
 #
 # Supported values are `mysql` and `mariadb`.
+##
 LOCAL_DB_TYPE=mysql
 
+##
 # The database version to use.
 #
 # Defaults to 5.7 with the assumption that LOCAL_DB_TYPE is set to `mysql` above.
 #
 # When using `mysql`, see https://hub.docker.com/_/mysql/ for valid versions.
 # When using `mariadb`, see https://hub.docker.com/_/mariadb for valid versions.
+##
 LOCAL_DB_VERSION=5.7
 
 # The debug settings to add to `wp-config.php`.
@@ -67,3 +71,10 @@ LOCAL_WP_ENVIRONMENT_TYPE=local
 
 # The URL to use when running e2e tests.
 WP_BASE_URL=http://localhost:${LOCAL_PORT}
+
+##
+# The revision number of the WordPress Importer plugin to use when running unit tests.
+#
+# This should be an SVN revision number from the official plugin repository on wordpress.org.
+##
+WP_IMPORTER_REVISION=2387243
diff --git a/.github/workflows/phpunit-tests.yml b/.github/workflows/phpunit-tests.yml
index 0d14901f5e..d6f1ed9bc2 100644
--- a/.github/workflows/phpunit-tests.yml
+++ b/.github/workflows/phpunit-tests.yml
@@ -24,7 +24,6 @@ jobs:
   # Performs the following steps:
   # - Cancels all previous workflow runs for pull requests that have not completed.
   # - Checks out the repository.
-  # - Checks out the WordPress Importer plugin (needed for the Core PHPUnit tests).
   # - Logs debug information about the runner container.
   # - Installs NodeJS 14.
   # - Sets up caching for NPM.
@@ -47,9 +46,6 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v2
 
-      - name: Checkout the WordPress Importer plugin
-        run: svn checkout -r 2387243 https://plugins.svn.wordpress.org/wordpress-importer/trunk/ tests/phpunit/data/plugins/wordpress-importer
-
       - name: Log debug information
         run: |
           echo "$GITHUB_REF"
diff --git a/tools/local-env/scripts/install.js b/tools/local-env/scripts/install.js
index 32371ee190..2bce37b03b 100644
--- a/tools/local-env/scripts/install.js
+++ b/tools/local-env/scripts/install.js
@@ -20,6 +20,8 @@ wp_cli( `config set WP_ENVIRONMENT_TYPE ${process.env.LOCAL_WP_ENVIRONMENT_TYPE}
 // Move wp-config.php to the base directory, so it doesn't get mixed up in the src or build directories.
 renameSync( 'src/wp-config.php', 'wp-config.php' );
 
+install_wp_importer();
+
 // Read in wp-tests-config-sample.php, edit it to work with our config, then write it to wp-tests-config.php.
 const testConfig = readFileSync( 'wp-tests-config-sample.php', 'utf8' )
 	.replace( 'youremptytestdbnamehere', 'wordpress_develop_tests' )
@@ -45,3 +47,12 @@ wait_on( { resources: [ `tcp:localhost:${process.env.LOCAL_PORT}`] } )
 function wp_cli( cmd ) {
 	execSync( `docker-compose run --rm cli ${cmd}`, { stdio: 'inherit' } );
 }
+
+/**
+ * Downloads the WordPress Importer plugin for use in tests.
+ */
+function install_wp_importer() {
+	const test_plugin_directory = 'tests/phpunit/data/plugins/wordpress-importer';
+
+	execSync( `docker-compose exec -T php rm -rf ${test_plugin_directory} && svn checkout -r ${process.env.WP_IMPORTER_REVISION} https://plugins.svn.wordpress.org/wordpress-importer/trunk/ ${test_plugin_directory}`, { stdio: 'inherit' } );
+}