registerSalesChannelDefinition example

$this->registerDefinitionWithExtensions(ProductDefinition::class, ProductExtension::class);

        $fields = $this->getContainer()
            ->get(DefinitionInstanceRegistry::class)
            ->get(ProductDefinition::class)
            ->getFields();
        static::assertTrue($fields->has('toOne'));
        static::assertInstanceOf(OneToOneAssociationField::class, $fields->get('toOne'));
        static::assertTrue($fields->has('oneToMany'));
        static::assertInstanceOf(OneToManyAssociationField::class, $fields->get('oneToMany'));

        $this->registerSalesChannelDefinition(ExtendedProductDefinition::class);
        $this->registerSalesChannelDefinitionWithExtensions(ProductDefinition::class, ProductExtension::class);
        $fields = $this->getContainer()
            ->get(SalesChannelDefinitionInstanceRegistry::class)
            ->get(ProductDefinition::class)
            ->getFields();
        static::assertTrue($fields->has('toOne'));
        static::assertInstanceOf(OneToOneAssociationField::class, $fields->get('toOne'));
        static::assertTrue($fields->has('oneToMany'));
        static::assertInstanceOf(OneToManyAssociationField::class, $fields->get('oneToMany'));

        $this->removeExtension(ProductExtension::class);
    }