diff --git a/.gitignore b/.gitignore
index 1fdff8f..d719189 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 composer.lock
 vendor
 /build/logs
+/infection.log
diff --git a/.travis.yml b/.travis.yml
index d93816d..05be5b0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,7 @@ env:
 install:
   - composer install --dev --no-scripts
 script:
-  - php vendor/bin/phpunit --coverage-clover build/logs/clover.xml --whitelist=src/
+  - composer ci
 after_success:
   - curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
   - chmod +x ./cc-test-reporter
diff --git a/composer.json b/composer.json
index 3d8ec43..902f5e5 100644
--- a/composer.json
+++ b/composer.json
@@ -13,14 +13,15 @@
         }
     ],
     "require": {
-        "symfony/filesystem": ">2.8",
-        "php": ">=7.1"
+        "php": ">=7.1",
+        "symfony/filesystem": ">2.8"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.4",
+        "phpunit/phpunit": "^7.0|^8.0",
         "jakub-onderka/php-parallel-lint": "^1.0",
-        "phpstan/phpstan-shim": "^0.10.5",
-        "keboola/coding-standard": "^6.0"
+        "phpstan/phpstan-shim": "^0.11",
+        "keboola/coding-standard": "^8.0",
+        "infection/infection": "^0.12"
     },
     "autoload": {
         "psr-4": {
@@ -33,15 +34,17 @@
         }
     },
     "scripts": {
-        "tests": "phpunit",
+        "tests": "phpunit --coverage-clover build/logs/clover.xml --coverage-xml=build/logs/coverage-xml --log-junit=build/logs/phpunit.junit.xml",
         "phpstan": "phpstan analyse ./src ./tests --level=max --no-progress -c phpstan.neon",
         "phpcs": "phpcs -n --ignore=vendor --extensions=php .",
         "phplint": "parallel-lint -j 10 --exclude vendor .",
+        "infection": "infection --threads=4 --min-covered-msi=80 --coverage=build/logs",
         "build": [
             "@phplint",
             "@phpcs",
             "@phpstan",
-            "@tests"
+            "@tests",
+            "@infection"
         ],
         "ci": [
             "@composer validate --no-check-publish --no-check-all",
diff --git a/infection.json.dist b/infection.json.dist
new file mode 100644
index 0000000..42f1627
--- /dev/null
+++ b/infection.json.dist
@@ -0,0 +1,14 @@
+{
+    "timeout": 10,
+    "source": {
+        "directories": [
+            "src\/"
+        ]
+    },
+    "logs": {
+        "text": "infection.log"
+    },
+    "mutators": {
+        "@default": true
+    }
+}
\ No newline at end of file
diff --git a/phpunit.xml b/phpunit.xml
index c8a890e..3289757 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -12,5 +12,12 @@
 	<testsuite name="Library Test Suite">
 		<directory>tests</directory>
 	</testsuite>
-
+	<filter>
+		<whitelist processUncoveredFilesFromWhitelist="true">
+			<directory suffix=".php">.</directory>
+			<exclude>
+				<directory suffix=".php">vendor</directory>
+			</exclude>
+		</whitelist>
+	</filter>
 </phpunit>
diff --git a/src/Temp.php b/src/Temp.php
index 3558302..2233252 100644
--- a/src/Temp.php
+++ b/src/Temp.php
@@ -8,6 +8,8 @@
 
 class Temp
 {
+    private const FILE_MODE = 0777;
+
     /**
      * @var String
      */
@@ -31,7 +33,7 @@ class Temp
     public function __construct(string $prefix = '')
     {
         $this->prefix = $prefix;
-        $this->id = uniqid("run-", true);
+        $this->id = uniqid('run-', true);
         $this->fileSystem = new Filesystem();
     }
 
@@ -39,9 +41,7 @@ private function initRunFolder(): void
     {
         clearstatcache();
         $path = $this->getTmpPath();
-        if (!file_exists($path) && !is_dir($path)) {
-            $this->fileSystem->mkdir($path, 0777);
-        }
+        $this->fileSystem->mkdir($path, self::FILE_MODE);
         $this->tmpFolder = $path;
     }
 
@@ -54,9 +54,9 @@ private function getTmpPath(): string
     {
         $tmpDir = sys_get_temp_dir();
         if (!empty($this->prefix)) {
-            $tmpDir .= "/" . $this->prefix;
+            $tmpDir .= '/' . $this->prefix;
         }
-        $tmpDir .= "/" . $this->id;
+        $tmpDir .= '/' . $this->id;
         return $tmpDir;
     }
 
@@ -101,10 +101,10 @@ public function createFile(string $fileName): \SplFileInfo
         $fileInfo = new \SplFileInfo($this->getTmpFolder() . '/' . $fileName);
         $pathName = $fileInfo->getPathname();
         if (!file_exists(dirname($pathName))) {
-            $this->fileSystem->mkdir(dirname($pathName), 0777);
+            $this->fileSystem->mkdir(dirname($pathName), self::FILE_MODE);
         }
         $this->fileSystem->touch($pathName);
-        $this->fileSystem->chmod($pathName, 0600);
+        $this->fileSystem->chmod($pathName, self::FILE_MODE);
         return $fileInfo;
     }
 
diff --git a/tests/TempTest.php b/tests/TempTest.php
index 5afbf17..f168e7e 100644
--- a/tests/TempTest.php
+++ b/tests/TempTest.php
@@ -16,7 +16,13 @@ public function testCreateTmpFile(): void
         $file = $temp->createTmpFile('filename_suffix');
 
         self::assertFileExists($file->getPathname());
-        self::assertContains($tempFolder, $file->getPathname());
+        self::assertStringContainsString($tempFolder, $file->getPathname());
+        self::assertStringEndsWith('-filename_suffix', $file->getFilename());
+        self::assertNotEquals('-filename_suffix', $file->getFilename());
+        $dirParts = explode('/', $file->getPath());
+        $tempDirName = (string) end($dirParts);
+        self::assertStringStartsWith('run-', $tempDirName);
+        self::assertGreaterThan(20, strlen($tempDirName));
     }
 
     public function testCreateFile(): void
@@ -26,6 +32,7 @@ public function testCreateFile(): void
 
         self::assertInstanceOf('SplFileInfo', $file);
         self::assertEquals($temp->getTmpFolder() . '/' . $file->getFilename(), $file->getPathname());
+        self::assertEquals('0777', substr(sprintf('%o', $file->getPerms()), -4));
     }
 
     public function testCreateFileNested(): void
@@ -42,7 +49,7 @@ public function testGetTmpFolder(): void
         $tempFolder = $temp->getTmpFolder();
 
         self::assertNotEmpty($tempFolder);
-        self::assertContains(sys_get_temp_dir() . '/test', $temp->getTmpFolder());
+        self::assertStringContainsString(sys_get_temp_dir() . '/test', $temp->getTmpFolder());
     }
 
     public function testCleanup(): void