ACP2E-3324: fix unit test future deprecations

Author: alzota

app/code/Magento/Theme/Test/Unit/Plugin/DesignPathValidatorPluginTest.php

@@ -70,10 +70,7 @@ public function testAroundValidateWithValidPath()
             ->willReturn([$path => $path]);
 
         $designConfig = $this->createMock(DesignConfigInterface::class);
-        $extensionAttributes = $this->getMockBuilder(DesignConfigExtensionInterface::class)
-            ->disableOriginalConstructor()
-            ->onlyMethods(['getDesignConfigData', 'setDesignConfigData'])
-            ->getMock();
+        $extensionAttributes = $this->createMock(DesignConfigDataCallableMockInterface::class);
         $designConfig->expects($this->once())
             ->method('getExtensionAttributes')
             ->willReturn($extensionAttributes);
@@ -114,7 +111,7 @@ public function testAroundValidateWithInvalidPath()
             ->willReturn([]);
 
         $designConfig = $this->createMock(DesignConfigInterface::class);
-        $extensionAttributes = $this->createMock(DesignConfigExtensionInterface::class);
+        $extensionAttributes = $this->createMock(DesignConfigDataCallableMockInterface::class);
         $designConfig->expects($this->once())
             ->method('getExtensionAttributes')
             ->willReturn($extensionAttributes);
@@ -130,3 +127,12 @@ public function testAroundValidateWithInvalidPath()
         $this->plugin->aroundValidate($pathValidator, $proceed, $path);
     }
 }
+
+// @codingStandardsIgnoreStart
+interface DesignConfigDataCallableMockInterface
+{
+    /**
+     * @return \Magento\Theme\Api\Data\DesignConfigDataInterface[]|null
+     */
+    public function getDesignConfigData();
+}