diff --git a/includes/core/class-image-pipeline.php b/includes/core/class-image-pipeline.php
index 1cdb085..02e1348 100644
--- a/includes/core/class-image-pipeline.php
+++ b/includes/core/class-image-pipeline.php
@@ -124,7 +124,9 @@ class PRAutoBlogger_Image_Pipeline {
 				? $image_a_result->get_error_message()
 				: 'Image A generation produced no attachment ID.';
 		}
-		$result['cost_usd'] += $image_a_result['cost_usd'] ?? 0.0;
+		if ( ! is_wp_error( $image_a_result ) ) {
+			$result['cost_usd'] += $image_a_result['cost_usd'] ?? 0.0;
+		}
 
 		// Generate Image B (source-driven prompt) if source data is available.
 		if ( null !== $source_data && ! empty( $source_data ) ) {
@@ -136,7 +138,9 @@ class PRAutoBlogger_Image_Pipeline {
 					? $image_b_result->get_error_message()
 					: 'Image B generation produced no attachment ID.';
 			}
-			$result['cost_usd'] += $image_b_result['cost_usd'] ?? 0.0;
+			if ( ! is_wp_error( $image_b_result ) ) {
+				$result['cost_usd'] += $image_b_result['cost_usd'] ?? 0.0;
+			}
 		}
 
 		return $result;
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 83714a7..6ff6748 100755
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -55,6 +55,11 @@ if ( ! defined( 'PRAUTOBLOGGER_DEFAULT_EDITOR_MODEL' ) ) {
     define( 'PRAUTOBLOGGER_DEFAULT_EDITOR_MODEL', 'google/gemini-2.5-flash-lite' );
 }
 
+// Default image style suffix used by ImagePromptBuilder and settings UI.
+if ( ! defined( 'PRAUTOBLOGGER_DEFAULT_IMAGE_STYLE_SUFFIX' ) ) {
+    define( 'PRAUTOBLOGGER_DEFAULT_IMAGE_STYLE_SUFFIX', 'Style: test infomercial style.' );
+}
+
 // WordPress database constants used in $wpdb queries.
 if ( ! defined( 'ARRAY_A' ) ) {
     define( 'ARRAY_A', 'ARRAY_A' );
diff --git a/tests/unit/Core/ImagePipelineTest.php b/tests/unit/Core/ImagePipelineTest.php
index 63e8164..d04b8a8 100644
--- a/tests/unit/Core/ImagePipelineTest.php
+++ b/tests/unit/Core/ImagePipelineTest.php
@@ -19,6 +19,9 @@ class ImagePipelineTest extends BaseTestCase {
 		parent::setUp();
 
 		// Mock WordPress functions used by the pipeline and its dependencies.
+		Functions\when( 'is_wp_error' )->alias( function ( $thing ) {
+			return $thing instanceof \WP_Error;
+		} );
 		Functions\when( 'wp_generate_uuid4' )->justReturn( 'test-uuid' );
 		Functions\when( 'get_option' )->alias( function ( $key, $default = false ) {
 			static $options = [
@@ -32,6 +35,8 @@ class ImagePipelineTest extends BaseTestCase {
 			return trim( strip_tags( $str ) );
 		} );
 		Functions\when( 'update_post_meta' )->justReturn( true );
+		Functions\when( 'sanitize_title' )->returnArg();
+		Functions\when( 'esc_html__' )->returnArg();
 	}
 
 	/**