diff --git a/inc/phpunit/bootstrap.php b/inc/phpunit/bootstrap.php
index 9112192..f9115d0 100644
--- a/inc/phpunit/bootstrap.php
+++ b/inc/phpunit/bootstrap.php
@@ -49,7 +49,6 @@
 /**
  * Setup ElasticPress on install.
  */
-define( 'EP_INDEX_PREFIX', 'tests_' );
 tests_add_filter( 'plugins_loaded', function () {
 	global $table_prefix;
 
@@ -85,11 +84,6 @@
 	}
 }, 21 );
 
-/**
- * Modify the cache keys to prevent conflicts.
- */
-define( 'WP_CACHE_KEY_SALT', 'phpunit' );
-
 // Load custom bootstrap code.
 if ( file_exists( Altis\PHPUNIT_PROJECT_ROOT . '/.config/tests-bootstrap.php' ) ) {
 	require Altis\PHPUNIT_PROJECT_ROOT . '/.config/tests-bootstrap.php';
diff --git a/inc/phpunit/config.php b/inc/phpunit/config.php
index d748248..ed30301 100644
--- a/inc/phpunit/config.php
+++ b/inc/phpunit/config.php
@@ -16,6 +16,12 @@
 defined( 'WP_TESTS_EMAIL' ) or define( 'WP_TESTS_EMAIL', 'admin@example.org' );
 defined( 'WP_TESTS_TITLE' ) or define( 'WP_TESTS_TITLE', 'Test Blog' );
 
+// Ensure cache key salt is different for test runs.
+defined( 'WP_CACHE_KEY_SALT' ) or define( 'WP_CACHE_KEY_SALT', 'phpunit' );
+
+// Ensure tests use their own ElasticPress indexes.
+defined( 'EP_INDEX_PREFIX' ) or define( 'EP_INDEX_PREFIX', 'tests_' );
+
 // Set tests table prefix.
 $table_prefix = 'wptests_';