diff --git a/.travis.yml b/.travis.yml
index 30e62386..80452372 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -32,6 +32,7 @@ before_script:
     - (cd tests/Application && bin/console doctrine:database:create --env=test -vvv)
     - (cd tests/Application && bin/console doctrine:schema:create --env=test -vvv)
     - (cd tests/Application && bin/console assets:install web --env=test -vvv)
+    - (cd tests/Application && bin/console cache:warmup --env=dev -vvv)
     - (cd tests/Application && yarn run gulp)
 
     # Configure display
@@ -65,10 +66,9 @@ before_script:
 
 script:
     - composer validate --strict
-    - bin/phpstan.phar analyse -c phpstan.neon -l max src/
+    - bin/phpstan analyse -c phpstan.neon -l max src/
     - bin/ecs check src/ spec/ tests/Behat/
 
-#    - bin/phpunit
     - bin/phpspec run
     - bin/behat features/ --strict -vvv --no-interaction || bin/behat features/ --strict -vvv --no-interaction --rerun
 
diff --git a/composer.json b/composer.json
index 900f4a24..fef370c3 100644
--- a/composer.json
+++ b/composer.json
@@ -34,7 +34,8 @@
         "friends-of-behat/variadic-extension": "^1.0",
         "lakion/mink-debug-extension": "^1.2.3",
         "phpspec/phpspec": "^3.2",
-        "phpstan/phpstan-shim": "^0.9.2",
+        "phpstan/phpstan-symfony": "^0.10.0",
+        "phpstan/phpstan-webmozart-assert": "^0.10.0",
         "phpunit/phpunit": "^5.6",
         "portphp/csv": "^1.1.0",
         "portphp/excel": "^1.1.0",
diff --git a/composer.lock b/composer.lock
index f9538833..249a12a1 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "872aea1950d60d71f59941aed6f2929c",
+    "content-hash": "e85bc9b443a1039506c8ddff0e5f1634",
     "packages": [
         {
             "name": "behat/transliterator",
@@ -8654,6 +8654,151 @@
             ],
             "time": "2018-05-29T17:25:09+00:00"
         },
+        {
+            "name": "nette/bootstrap",
+            "version": "v2.4.6",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nette/bootstrap.git",
+                "reference": "268816e3f1bb7426c3a4ceec2bd38a036b532543"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nette/bootstrap/zipball/268816e3f1bb7426c3a4ceec2bd38a036b532543",
+                "reference": "268816e3f1bb7426c3a4ceec2bd38a036b532543",
+                "shasum": ""
+            },
+            "require": {
+                "nette/di": "~2.4.7",
+                "nette/utils": "~2.4",
+                "php": ">=5.6.0"
+            },
+            "conflict": {
+                "nette/nette": "<2.2"
+            },
+            "require-dev": {
+                "latte/latte": "~2.2",
+                "nette/application": "~2.3",
+                "nette/caching": "~2.3",
+                "nette/database": "~2.3",
+                "nette/forms": "~2.3",
+                "nette/http": "~2.4.0",
+                "nette/mail": "~2.3",
+                "nette/robot-loader": "^2.4.2 || ^3.0",
+                "nette/safe-stream": "~2.2",
+                "nette/security": "~2.3",
+                "nette/tester": "~2.0",
+                "tracy/tracy": "^2.4.1"
+            },
+            "suggest": {
+                "nette/robot-loader": "to use Configurator::createRobotLoader()",
+                "tracy/tracy": "to use Configurator::enableTracy()"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.4-dev"
+                }
+            },
+            "autoload": {
+                "classmap": [
+                    "src/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause",
+                "GPL-2.0",
+                "GPL-3.0"
+            ],
+            "authors": [
+                {
+                    "name": "David Grudl",
+                    "homepage": "https://davidgrudl.com"
+                },
+                {
+                    "name": "Nette Community",
+                    "homepage": "https://nette.org/contributors"
+                }
+            ],
+            "description": "🅱 Nette Bootstrap: the simple way to configure and bootstrap your Nette application.",
+            "homepage": "https://nette.org",
+            "keywords": [
+                "bootstrapping",
+                "configurator",
+                "nette"
+            ],
+            "time": "2018-05-17T12:52:20+00:00"
+        },
+        {
+            "name": "nette/di",
+            "version": "v2.4.13",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nette/di.git",
+                "reference": "3f8f212b02d5c17feb97a7e0a39ab306f40c06ca"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nette/di/zipball/3f8f212b02d5c17feb97a7e0a39ab306f40c06ca",
+                "reference": "3f8f212b02d5c17feb97a7e0a39ab306f40c06ca",
+                "shasum": ""
+            },
+            "require": {
+                "ext-tokenizer": "*",
+                "nette/neon": "^2.3.3 || ~3.0.0",
+                "nette/php-generator": "^2.6.1 || ~3.0.0",
+                "nette/utils": "^2.4.3 || ~3.0.0",
+                "php": ">=5.6.0"
+            },
+            "conflict": {
+                "nette/bootstrap": "<2.4",
+                "nette/nette": "<2.2"
+            },
+            "require-dev": {
+                "nette/tester": "^2.0",
+                "tracy/tracy": "^2.3"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.4-dev"
+                }
+            },
+            "autoload": {
+                "classmap": [
+                    "src/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause",
+                "GPL-2.0",
+                "GPL-3.0"
+            ],
+            "authors": [
+                {
+                    "name": "David Grudl",
+                    "homepage": "https://davidgrudl.com"
+                },
+                {
+                    "name": "Nette Community",
+                    "homepage": "https://nette.org/contributors"
+                }
+            ],
+            "description": "💎 Nette Dependency Injection Container: Flexible, compiled and full-featured DIC with perfectly usable autowiring and support for all new PHP 7.1 features.",
+            "homepage": "https://nette.org",
+            "keywords": [
+                "compiled",
+                "di",
+                "dic",
+                "factory",
+                "ioc",
+                "nette",
+                "static"
+            ],
+            "time": "2018-06-11T08:46:01+00:00"
+        },
         {
             "name": "nette/finder",
             "version": "v2.4.2",
@@ -8716,6 +8861,129 @@
             ],
             "time": "2018-06-28T11:49:23+00:00"
         },
+        {
+            "name": "nette/neon",
+            "version": "v2.4.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nette/neon.git",
+                "reference": "5e72b1dd3e2d34f0863c5561139a19df6a1ef398"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nette/neon/zipball/5e72b1dd3e2d34f0863c5561139a19df6a1ef398",
+                "reference": "5e72b1dd3e2d34f0863c5561139a19df6a1ef398",
+                "shasum": ""
+            },
+            "require": {
+                "ext-iconv": "*",
+                "ext-json": "*",
+                "php": ">=5.6.0"
+            },
+            "require-dev": {
+                "nette/tester": "~2.0",
+                "tracy/tracy": "^2.3"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.4-dev"
+                }
+            },
+            "autoload": {
+                "classmap": [
+                    "src/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause",
+                "GPL-2.0",
+                "GPL-3.0"
+            ],
+            "authors": [
+                {
+                    "name": "David Grudl",
+                    "homepage": "https://davidgrudl.com"
+                },
+                {
+                    "name": "Nette Community",
+                    "homepage": "https://nette.org/contributors"
+                }
+            ],
+            "description": "🍸 Nette NEON: encodes and decodes NEON file format.",
+            "homepage": "http://ne-on.org",
+            "keywords": [
+                "export",
+                "import",
+                "neon",
+                "nette",
+                "yaml"
+            ],
+            "time": "2018-03-21T12:12:21+00:00"
+        },
+        {
+            "name": "nette/php-generator",
+            "version": "v3.0.4",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nette/php-generator.git",
+                "reference": "b381ecacbf5a0b5f99cc0b303d5b0578d409f446"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nette/php-generator/zipball/b381ecacbf5a0b5f99cc0b303d5b0578d409f446",
+                "reference": "b381ecacbf5a0b5f99cc0b303d5b0578d409f446",
+                "shasum": ""
+            },
+            "require": {
+                "nette/utils": "^2.4.2 || ~3.0.0",
+                "php": ">=7.0"
+            },
+            "conflict": {
+                "nette/nette": "<2.2"
+            },
+            "require-dev": {
+                "nette/tester": "^2.0",
+                "tracy/tracy": "^2.3"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.0-dev"
+                }
+            },
+            "autoload": {
+                "classmap": [
+                    "src/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause",
+                "GPL-2.0",
+                "GPL-3.0"
+            ],
+            "authors": [
+                {
+                    "name": "David Grudl",
+                    "homepage": "https://davidgrudl.com"
+                },
+                {
+                    "name": "Nette Community",
+                    "homepage": "https://nette.org/contributors"
+                }
+            ],
+            "description": "🐘 Nette PHP Generator: generates neat PHP code for you. Supports new PHP 7.2 features.",
+            "homepage": "https://nette.org",
+            "keywords": [
+                "code",
+                "nette",
+                "php",
+                "scaffolding"
+            ],
+            "time": "2018-04-26T16:48:20+00:00"
+        },
         {
             "name": "nette/robot-loader",
             "version": "v3.0.4",
@@ -8863,6 +9131,57 @@
             ],
             "time": "2018-05-02T17:16:08+00:00"
         },
+        {
+            "name": "nikic/php-parser",
+            "version": "v4.0.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nikic/PHP-Parser.git",
+                "reference": "bd088dc940a418f09cda079a9b5c7c478890fb8d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nikic/PHP-Parser/zipball/bd088dc940a418f09cda079a9b5c7c478890fb8d",
+                "reference": "bd088dc940a418f09cda079a9b5c7c478890fb8d",
+                "shasum": ""
+            },
+            "require": {
+                "ext-tokenizer": "*",
+                "php": ">=7.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^6.5 || ^7.0"
+            },
+            "bin": [
+                "bin/php-parse"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "4.0-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "PhpParser\\": "lib/PhpParser"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause"
+            ],
+            "authors": [
+                {
+                    "name": "Nikita Popov"
+                }
+            ],
+            "description": "A PHP parser written in PHP",
+            "keywords": [
+                "parser",
+                "php"
+            ],
+            "time": "2018-07-15T17:25:16+00:00"
+        },
         {
             "name": "php-cs-fixer/diff",
             "version": "v1.3.0",
@@ -9354,41 +9673,181 @@
             "time": "2018-06-20T17:48:01+00:00"
         },
         {
-            "name": "phpstan/phpstan-shim",
-            "version": "0.9.2",
+            "name": "phpstan/phpstan",
+            "version": "0.10.2",
             "source": {
                 "type": "git",
-                "url": "https://github.com/phpstan/phpstan-shim.git",
-                "reference": "e4720fb2916be05de02869780072253e7e0e8a75"
+                "url": "https://github.com/phpstan/phpstan.git",
+                "reference": "d69658794514e57ad9f247e623513397038f362f"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpstan/phpstan-shim/zipball/e4720fb2916be05de02869780072253e7e0e8a75",
-                "reference": "e4720fb2916be05de02869780072253e7e0e8a75",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/d69658794514e57ad9f247e623513397038f362f",
+                "reference": "d69658794514e57ad9f247e623513397038f362f",
                 "shasum": ""
             },
             "require": {
-                "php": "~7.0"
-            },
-            "replace": {
-                "phpstan/phpstan": "self.version"
+                "composer/xdebug-handler": "^1.0",
+                "jean85/pretty-package-versions": "^1.0.3",
+                "nette/bootstrap": "^2.4 || ^3.0",
+                "nette/di": "^2.4.7 || ^3.0",
+                "nette/robot-loader": "^3.0.1",
+                "nette/utils": "^2.4.5 || ^3.0",
+                "nikic/php-parser": "^4.0.2",
+                "php": "~7.1",
+                "phpstan/phpdoc-parser": "^0.3",
+                "symfony/console": "~3.2 || ~4.0",
+                "symfony/finder": "~3.2 || ~4.0"
+            },
+            "require-dev": {
+                "brianium/paratest": "^2.0",
+                "consistence/coding-standard": "^3.3",
+                "dealerdirect/phpcodesniffer-composer-installer": "^0.4.4",
+                "ext-gd": "*",
+                "ext-intl": "*",
+                "ext-mysqli": "*",
+                "ext-zip": "*",
+                "jakub-onderka/php-parallel-lint": "^1.0",
+                "localheinz/composer-normalize": "~0.8.0",
+                "phing/phing": "^2.16.0",
+                "phpstan/phpstan-deprecation-rules": "^0.10.2",
+                "phpstan/phpstan-php-parser": "^0.10",
+                "phpstan/phpstan-phpunit": "^0.10",
+                "phpstan/phpstan-strict-rules": "^0.10",
+                "phpunit/phpunit": "^7.0",
+                "slevomat/coding-standard": "^4.6.2"
             },
             "bin": [
-                "phpstan",
-                "phpstan.phar"
+                "bin/phpstan"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "0.10-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "PHPStan\\": [
+                        "src/",
+                        "build/PHPStan"
+                    ]
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "PHPStan - PHP Static Analysis Tool",
+            "time": "2018-07-22T17:55:11+00:00"
+        },
+        {
+            "name": "phpstan/phpstan-symfony",
+            "version": "0.10",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/phpstan-symfony.git",
+                "reference": "34b1940a678768ba1b957ca550f99bf7c81f6222"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/phpstan-symfony/zipball/34b1940a678768ba1b957ca550f99bf7c81f6222",
+                "reference": "34b1940a678768ba1b957ca550f99bf7c81f6222",
+                "shasum": ""
+            },
+            "require": {
+                "ext-simplexml": "*",
+                "nikic/php-parser": "^4.0",
+                "php": "^7.1",
+                "phpstan/phpstan": "^0.10"
+            },
+            "conflict": {
+                "symfony/framework-bundle": "<3.0"
+            },
+            "require-dev": {
+                "consistence/coding-standard": "^3.0.1",
+                "dealerdirect/phpcodesniffer-composer-installer": "^0.4.4",
+                "jakub-onderka/php-parallel-lint": "^1.0",
+                "phing/phing": "^2.16.0",
+                "phpstan/phpstan-phpunit": "^0.10",
+                "phpstan/phpstan-strict-rules": "^0.10",
+                "phpunit/phpunit": "^7.0",
+                "satooshi/php-coveralls": "^1.0",
+                "slevomat/coding-standard": "^4.5.2",
+                "symfony/framework-bundle": "^3.0 || ^4.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "0.10-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "PHPStan\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Lukáš Unger",
+                    "email": "looky.msc@gmail.com",
+                    "homepage": "https://lookyman.net"
+                }
             ],
+            "description": "Symfony Framework extensions and rules for PHPStan",
+            "time": "2018-06-21T12:00:50+00:00"
+        },
+        {
+            "name": "phpstan/phpstan-webmozart-assert",
+            "version": "0.10",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/phpstan-webmozart-assert.git",
+                "reference": "5954bb88827ae8e4b45ee5db4f430c1ced69818a"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/phpstan-webmozart-assert/zipball/5954bb88827ae8e4b45ee5db4f430c1ced69818a",
+                "reference": "5954bb88827ae8e4b45ee5db4f430c1ced69818a",
+                "shasum": ""
+            },
+            "require": {
+                "nikic/php-parser": "^4.0",
+                "php": "~7.1",
+                "phpstan/phpstan": "^0.10"
+            },
+            "require-dev": {
+                "consistence/coding-standard": "^3.0.1",
+                "dealerdirect/phpcodesniffer-composer-installer": "^0.4.4",
+                "jakub-onderka/php-parallel-lint": "^1.0",
+                "phing/phing": "^2.16.0",
+                "phpstan/phpstan-phpunit": "^0.10",
+                "phpstan/phpstan-strict-rules": "^0.10",
+                "phpunit/phpunit": "^7.1.3",
+                "slevomat/coding-standard": "^4.5.2",
+                "webmozart/assert": "^1.3.0"
+            },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "0.9-dev"
+                    "dev-master": "0.10-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "PHPStan\\": "src/"
                 }
             },
             "notification-url": "https://packagist.org/downloads/",
             "license": [
                 "MIT"
             ],
-            "description": "PHPStan Phar distribution",
-            "time": "2018-01-28T14:29:27+00:00"
+            "description": "PHPStan webmozart/assert extension",
+            "time": "2018-06-23T17:24:59+00:00"
         },
         {
             "name": "phpunit/php-code-coverage",
diff --git a/phpstan.neon b/phpstan.neon
index 1cbc5e8d..a933d7a7 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,4 +1,11 @@
+includes:
+	- vendor/phpstan/phpstan-symfony/extension.neon
+	- vendor/phpstan/phpstan-webmozart-assert/extension.neon
+
 parameters:
+    symfony:
+        container_xml_path: tests/Application/var/cache/dev/appDevDebugProjectContainer.xml
+
     excludes_analyse:
         # Makes PHPStan crash
         - 'src/DependencyInjection/Configuration.php'
diff --git a/src/Controller/ImportDataController.php b/src/Controller/ImportDataController.php
index cbc317ca..36ef6cc1 100644
--- a/src/Controller/ImportDataController.php
+++ b/src/Controller/ImportDataController.php
@@ -4,6 +4,7 @@
 
 namespace FriendsOfSylius\SyliusImportExportPlugin\Controller;
 
+use FriendsOfSylius\SyliusImportExportPlugin\Exception\ImporterException;
 use FriendsOfSylius\SyliusImportExportPlugin\Form\ImportType;
 use FriendsOfSylius\SyliusImportExportPlugin\Importer\ImporterInterface;
 use FriendsOfSylius\SyliusImportExportPlugin\Importer\ImporterRegistry;
@@ -79,7 +80,7 @@ public function importAction(Request $request): RedirectResponse
         if ($form->isSubmitted() && $form->isValid()) {
             $this->importData($importer, $form);
         }
-        $referer = (string) $request->headers->get('referer');
+        $referer = $request->headers->get('referer');
 
         return new RedirectResponse($referer);
     }
@@ -102,7 +103,11 @@ private function importData(string $importer, FormInterface $form): void
         $file = $form->get('import-data')->getData();
         /** @var ImporterInterface $service */
         $service = $this->registry->get($name);
-        $result = $service->import($file->getRealPath());
+        $path = $file->getRealPath();
+        if (false === $path) {
+            throw new ImporterException(sprintf('File %s could not be loaded', $file->getClientOriginalName()));
+        }
+        $result = $service->import($path);
 
         $message = sprintf(
             'Imported via %s importer (Time taken in ms: %s, Imported %s, Skipped %s, Failed %s)',
diff --git a/src/Exporter/JsonResourceExporter.php b/src/Exporter/JsonResourceExporter.php
index d9d5a554..7ecde63b 100644
--- a/src/Exporter/JsonResourceExporter.php
+++ b/src/Exporter/JsonResourceExporter.php
@@ -50,7 +50,7 @@ public function export(array $idsToExport): void
      */
     public function getExportedData(): string
     {
-        return json_encode($this->data);
+        return json_encode($this->data) ?: '';
     }
 
     /**
diff --git a/src/Exporter/MqItemWriter.php b/src/Exporter/MqItemWriter.php
index b2d815c0..2ce5e194 100644
--- a/src/Exporter/MqItemWriter.php
+++ b/src/Exporter/MqItemWriter.php
@@ -50,7 +50,7 @@ public function write(array $items): void
     {
         foreach ($items as $item) {
             $message = $this->redisContext->createMessage(
-                json_encode($item),
+                json_encode($item) ?: '',
                 [],
                 ['recordedOn' => (new \DateTime())->format('Y-m-d H:i:s')]
             );
diff --git a/src/Importer/JsonResourceImporter.php b/src/Importer/JsonResourceImporter.php
index b12a185f..79a5dd0a 100644
--- a/src/Importer/JsonResourceImporter.php
+++ b/src/Importer/JsonResourceImporter.php
@@ -5,6 +5,7 @@
 namespace FriendsOfSylius\SyliusImportExportPlugin\Importer;
 
 use Doctrine\Common\Persistence\ObjectManager;
+use FriendsOfSylius\SyliusImportExportPlugin\Exception\ImporterException;
 use FriendsOfSylius\SyliusImportExportPlugin\Processor\ResourceProcessorInterface;
 
 final class JsonResourceImporter extends ResourceImporter implements SingleDataArrayImporterInterface
@@ -32,9 +33,12 @@ public function import(string $fileName): ImporterResultInterface
     {
         $this->result->start();
 
-        $dataAsArray = json_decode(file_get_contents($fileName), true);
+        $contents = file_get_contents($fileName);
+        if (false === $contents) {
+            throw new ImporterException(sprintf('File %s could not be loaded', $fileName));
+        }
 
-        foreach ($dataAsArray as $i => $row) {
+        foreach (json_decode($contents, true) as $i => $row) {
             if ($this->importData($i, $row)) {
                 break;
             }
diff --git a/src/Importer/ResourceImporter.php b/src/Importer/ResourceImporter.php
index 7f0c80f9..aab0bf64 100644
--- a/src/Importer/ResourceImporter.php
+++ b/src/Importer/ResourceImporter.php
@@ -50,7 +50,7 @@ class ResourceImporter implements ImporterInterface
     /**
      * @var int
      */
-    private $batchCount;
+    private $batchCount = 0;
 
     public function __construct(
         ReaderFactory $readerFactory,
@@ -76,9 +76,8 @@ public function import(string $fileName): ImporterResultInterface
 
         $this->result->start();
 
-        $this->batchCount = 0;
         foreach ($reader as $i => $row) {
-            if ($this->importData($i, $row)) {
+            if ($this->importData((int) $i, $row)) {
                 break;
             }
         }
diff --git a/src/Writer/CsvWriter.php b/src/Writer/CsvWriter.php
index ceab46ab..6e58b447 100644
--- a/src/Writer/CsvWriter.php
+++ b/src/Writer/CsvWriter.php
@@ -4,6 +4,7 @@
 
 namespace FriendsOfSylius\SyliusImportExportPlugin\Writer;
 
+use FriendsOfSylius\SyliusImportExportPlugin\Exception\ExporterException;
 use Port\Csv\CsvWriter as PortCsvWriter;
 
 class CsvWriter implements WriterInterface
@@ -42,6 +43,9 @@ public function getFileContent(): string
 
         rewind($this->writer->getStream());
         $contents = stream_get_contents($this->writer->getStream());
+        if (false === $contents) {
+            throw new ExporterException(sprintf('Data stream could not be opened'));
+        }
 
         $this->finish();
 
diff --git a/src/Writer/ExcelWriter.php b/src/Writer/ExcelWriter.php
index dd121388..5a752c20 100644
--- a/src/Writer/ExcelWriter.php
+++ b/src/Writer/ExcelWriter.php
@@ -4,6 +4,7 @@
 
 namespace FriendsOfSylius\SyliusImportExportPlugin\Writer;
 
+use FriendsOfSylius\SyliusImportExportPlugin\Exception\ExporterException;
 use FriendsOfSylius\SyliusImportExportPlugin\Exception\InvalidOrderException;
 use Port\Excel\ExcelWriter as PortExcelWriter;
 
@@ -59,6 +60,9 @@ public function getFileContent(): string
         $this->finish();
 
         $contents = file_get_contents($this->filename);
+        if (false === $contents) {
+            throw new ExporterException(sprintf('File %s could not be loaded', $this->filename));
+        }
 
         unlink($this->filename);
 
@@ -68,7 +72,11 @@ public function getFileContent(): string
     private function prepare(): void
     {
         if (null === $this->filename) {
-            $this->filename = tempnam($this->temporaryFolder, 'exp');
+            $tmp = tempnam($this->temporaryFolder, 'exp');
+            if (false === $tmp) {
+                throw new ExporterException(sprintf('Could not create temporary file in "%s"', $this->temporaryFolder));
+            }
+            $this->filename = $tmp;
         }
 
         if (null === $this->writer) {
diff --git a/tests/Application/app/AppKernel.php b/tests/Application/app/AppKernel.php
index b84745b3..2846ca67 100644
--- a/tests/Application/app/AppKernel.php
+++ b/tests/Application/app/AppKernel.php
@@ -30,20 +30,4 @@ public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load($this->getRootDir() . '/config/config.yml');
     }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getCacheDir(): string
-    {
-        return sprintf('%s/%s/cache', sys_get_temp_dir(), md5(__DIR__));
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getLogDir(): string
-    {
-        return sprintf('%s/%s/logs', sys_get_temp_dir(), md5(__DIR__));
-    }
 }