diff --git a/.travis.yml b/.travis.yml
index 3253115..ffa7656 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,9 @@
 language: php
 dist: trusty
 php:
+  - "7.4"
+  - "7.3"
+  - "7.2"
   - "7.1"
   - "7.0"
   - "5.6"
diff --git a/composer.json b/composer.json
index 569c0c3..fc97ae1 100644
--- a/composer.json
+++ b/composer.json
@@ -15,9 +15,17 @@
         "mikehaertl/php-shellcommand": "^1.5.0",
         "mikehaertl/php-tmpfile": "^1.1.0"
     },
+    "require-dev": {
+        "phpunit/phpunit": ">4.0 <8"
+    },
     "autoload": {
         "psr-4": {
             "mikehaertl\\pdftk\\": "src/"
         }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "tests\\": "tests"
+        }
     }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 3a31f11..d4a86b0 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -8,7 +8,6 @@
          convertWarningsToExceptions="true"
          processIsolation="false"
          stopOnFailure="false"
-         syntaxCheck="false"
          bootstrap="./tests/bootstrap.php"
 >
     <testsuites>
diff --git a/tests/CommandTest.php b/tests/CommandTest.php
index 413f7b9..5ebedc9 100644
--- a/tests/CommandTest.php
+++ b/tests/CommandTest.php
@@ -1,7 +1,10 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\Command;
 
-class CommandTest extends \PHPUnit\Framework\TestCase
+class CommandTest extends TestCase
 {
     public function setUp()
     {
@@ -26,7 +29,7 @@ public function testCanAddFiles()
         $this->assertTrue($command->execute($file));
         $this->assertFileExists($file);
 
-        $this->assertEquals("pdftk A='$document1' B='$document2' input_pw B='complex'\''\"password' output '$file'", (string) $command);
+        $this->assertEquals("pdftk 'A'='$document1' 'B'='$document2' 'input_pw' 'B'='complex'\''\"password' 'output' '$file'", (string) $command);
     }
 
     public function testCanAddOptions()
@@ -42,7 +45,7 @@ public function testCanAddOptions()
         $this->assertTrue($command->execute($file));
         $this->assertFileExists($file);
 
-        $this->assertEquals("pdftk A='$document1' output '$file' encrypt_40bit allow Printing owner_pw 'complex'\''\"password'", (string) $command);
+        $this->assertEquals("pdftk 'A'='$document1' 'output' '$file' 'encrypt_40bit' allow Printing 'owner_pw' 'complex'\''\"password'", (string) $command);
     }
 
     public function testCanSetAndGetOperationAndArgument()
@@ -59,7 +62,7 @@ public function testCanSetAndGetOperationAndArgument()
 
         $this->assertEquals('cat', $command->getOperation());
         $this->assertEquals('A', $command->getOperationArgument());
-        $this->assertEquals("pdftk A='$document1' cat A output '$file'", (string) $command);
+        $this->assertEquals("pdftk 'A'='$document1' cat A 'output' '$file'", (string) $command);
     }
 
     public function testCanAddPageRanges()
@@ -86,7 +89,7 @@ public function testCanAddPageRanges()
         $this->assertTrue($command->execute($file));
         $this->assertFileExists($file);
 
-        $this->assertEquals("pdftk A='$document1' cat 1 A1 1-3 1-3even 1-3evennorth 1-3north A1-3 A1-3even A1-3oddeast A1-3east 1-3east 1 3 A1 A3 output '$file'", (string) $command);
+        $this->assertEquals("pdftk 'A'='$document1' cat 1 A1 1-3 1-3even 1-3evennorth 1-3north A1-3 A1-3even A1-3oddeast A1-3east 1-3east 1 3 A1 A3 'output' '$file'", (string) $command);
     }
 
     protected function getDocument1()
diff --git a/tests/DataFieldsTest.php b/tests/DataFieldsTest.php
index 4cd60d8..810eb1c 100644
--- a/tests/DataFieldsTest.php
+++ b/tests/DataFieldsTest.php
@@ -1,7 +1,10 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\DataFields;
 
-class DataFieldsTest extends \PHPUnit\Framework\TestCase
+class DataFieldsTest extends TestCase
 {
     public function testDataFieldParsing()
     {
diff --git a/tests/FdfFileTest.php b/tests/FdfFileTest.php
index 3650d32..e05c839 100644
--- a/tests/FdfFileTest.php
+++ b/tests/FdfFileTest.php
@@ -1,7 +1,10 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\FdfFile;
 
-class FdfFileTest extends \PHPUnit\Framework\TestCase
+class FdfFileTest extends TestCase
 {
     public function testFdfFileCreation()
     {
diff --git a/tests/InfoFieldsTest.php b/tests/InfoFieldsTest.php
index b299f9d..16d3fc7 100644
--- a/tests/InfoFieldsTest.php
+++ b/tests/InfoFieldsTest.php
@@ -1,7 +1,10 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\InfoFields;
 
-class InfoFieldsTest extends \PHPUnit\Framework\TestCase
+class InfoFieldsTest extends TestCase
 {
     public function testInfoFieldParsing()
     {
diff --git a/tests/InfoFileTest.php b/tests/InfoFileTest.php
index 05f95bf..b9236bc 100644
--- a/tests/InfoFileTest.php
+++ b/tests/InfoFileTest.php
@@ -1,7 +1,10 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\InfoFile;
 
-class InfoFileTest extends \PHPUnit\Framework\TestCase
+class InfoFileTest extends TestCase
 {
     public function testInfoFileCreation()
     {
diff --git a/tests/PdfTest.php b/tests/PdfTest.php
index 7b1e37b..29f77f2 100644
--- a/tests/PdfTest.php
+++ b/tests/PdfTest.php
@@ -1,8 +1,11 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\Pdf;
 use mikehaertl\pdftk\FdfFile;
 
-class PdfTest extends \PHPUnit\Framework\TestCase
+class PdfTest extends TestCase
 {
     public function setUp()
     {
@@ -25,7 +28,7 @@ public function testCanPassDocumentToConstructor()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
     public function testCanPassPdfInstanceToConstructor()
     {
@@ -45,7 +48,7 @@ public function testCanPassPdfInstanceToConstructor()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf2->getTmpFile();
-        $this->assertEquals("pdftk A='$outFile1' output '$tmpFile'", (string) $pdf2->getCommand());
+        $this->assertEquals("pdftk 'A'='$outFile1' 'output' '$tmpFile'", (string) $pdf2->getCommand());
     }
     public function testCanPassDocumentsToConstructor()
     {
@@ -61,7 +64,7 @@ public function testCanPassDocumentsToConstructor()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document1' B='$document2' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document1' 'B'='$document2' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
     public function testCanPassPdfInstancesToConstructor()
     {
@@ -91,7 +94,7 @@ public function testCanPassPdfInstancesToConstructor()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$outFile1' B='$outFile2' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$outFile1' 'B'='$outFile2' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
     public function testCanPassDocumentsWithPasswordToConstructor()
     {
@@ -108,7 +111,7 @@ public function testCanPassDocumentsWithPasswordToConstructor()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertEquals(
-            "pdftk A='$document1' B='$document2' input_pw A='complex'\''\"password' output '$tmpFile'",
+            "pdftk 'A'='$document1' 'B'='$document2' 'input_pw' 'A'='complex'\''\"password' 'output' '$tmpFile'",
             (string) $pdf->getCommand()
         );
     }
@@ -126,7 +129,7 @@ public function testCanAddFiles()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertEquals(
-            "pdftk A='$document1' D='$document2' input_pw A='complex'\''\"password' output '$tmpFile'",
+            "pdftk 'A'='$document1' 'D'='$document2' 'input_pw' 'A'='complex'\''\"password' 'output' '$tmpFile'",
             (string) $pdf->getCommand()
         );
     }
@@ -143,7 +146,7 @@ public function testCanPerformEmptyOperation()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertEquals(
-            "pdftk A='$document1' input_pw A='complex'\''\"password' output '$tmpFile'",
+            "pdftk 'A'='$document1' 'input_pw' 'A'='complex'\''\"password' 'output' '$tmpFile'",
             (string) $pdf->getCommand()
         );
     }
@@ -165,7 +168,7 @@ public function testCanCatFile()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertEquals(
-            "pdftk A='$document' cat 1-5 2 3 4 end-2even 3-5east 4-8eveneast 1south output '$tmpFile'",
+            "pdftk 'A'='$document' cat 1-5 2 3 4 end-2even 3-5east 4-8eveneast 1south 'output' '$tmpFile'",
             (string) $pdf->getCommand()
         );
     }
@@ -191,7 +194,7 @@ public function testCanCatFiles()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertEquals(
-            "pdftk A='$document1' B='$document2' cat A1-5 2 3 4 Bend-2even A3-5east B4-8eveneast A1south output '$tmpFile'",
+            "pdftk 'A'='$document1' 'B'='$document2' cat A1-5 2 3 4 Bend-2even A3-5east B4-8eveneast A1south 'output' '$tmpFile'",
             (string) $pdf->getCommand()
         );
     }
@@ -217,7 +220,7 @@ public function testCanShuffleFiles()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertEquals(
-            "pdftk A='$document1' B='$document2' shuffle A1-5 2 3 4 Bend-2even A3-5east B4-8eveneast A1south output '$tmpFile'",
+            "pdftk 'A'='$document1' 'B'='$document2' shuffle A1-5 2 3 4 Bend-2even A3-5east B4-8eveneast A1south 'output' '$tmpFile'",
             (string) $pdf->getCommand()
         );
     }
@@ -287,7 +290,7 @@ public function testCanFillFormFromData()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertRegExp(
-            "#pdftk A='$form' fill_form '/tmp/[^ ]+\.xfdf' output '$tmpFile' drop_xfa need_appearances#",
+            "#pdftk 'A'='$form' 'fill_form' '/tmp/[^ ]+\.xfdf' 'output' '$tmpFile' 'drop_xfa' 'need_appearances'#",
             (string) $pdf->getCommand()
         );
     }
@@ -307,7 +310,7 @@ public function testCanFillFormFromFile()
 
         $tmpFile = (string) $pdf->getTmpFile();
         $this->assertRegExp(
-            "#pdftk A='$form' fill_form '$fdf' output '$tmpFile' drop_xfa need_appearances#",
+            "#pdftk 'A'='$form' 'fill_form' '$fdf' 'output' '$tmpFile' 'drop_xfa' 'need_appearances'#",
             (string) $pdf->getCommand()
         );
     }
@@ -316,15 +319,15 @@ public function testCanUpdateInfo()
     {
         $document1 = $this->getDocument1();
         $file = $this->getOutFile();
-        
+
         $pdf = new Pdf($document1);
         $this->assertInstanceOf('mikehaertl\pdftk\Pdf', $pdf->updateInfo([
             'Creator' => 'php-pdftk'
         ]));
         $this->assertTrue($pdf->saveAs($file));
-        
+
         $this->assertFileExists($file);
-        
+
         $tmpFile = (string) $pdf->getTmpFile();
         $pdf = new Pdf($file);
         $data = $pdf->getData();
@@ -343,7 +346,7 @@ public function testCanSetBackground()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document1' background '$document2' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document1' 'background' '$document2' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
 
     public function testCanSetMultiBackground()
@@ -358,7 +361,7 @@ public function testCanSetMultiBackground()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document1' multibackground '$document2' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document1' 'multibackground' '$document2' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
 
     public function testCanStamp()
@@ -373,7 +376,7 @@ public function testCanStamp()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document1' stamp '$document2' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document1' 'stamp' '$document2' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
 
     public function testCanMultiStamp()
@@ -388,7 +391,7 @@ public function testCanMultiStamp()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document1' multistamp '$document2' output '$tmpFile'", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document1' 'multistamp' '$document2' 'output' '$tmpFile'", (string) $pdf->getCommand());
     }
 
     public function testCanRemovePermissions()
@@ -402,7 +405,7 @@ public function testCanRemovePermissions()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' allow", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'allow'", (string) $pdf->getCommand());
     }
 
     public function testCanSetPermissions()
@@ -416,7 +419,7 @@ public function testCanSetPermissions()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' allow Assembly CopyContents", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' allow Assembly CopyContents", (string) $pdf->getCommand());
     }
 
     public function testCanFlatten()
@@ -430,7 +433,7 @@ public function testCanFlatten()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' flatten", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'flatten'", (string) $pdf->getCommand());
     }
 
     public function testCanCompress()
@@ -444,7 +447,7 @@ public function testCanCompress()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' compress", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'compress'", (string) $pdf->getCommand());
     }
 
     public function testCanUncompress()
@@ -458,7 +461,7 @@ public function testCanUncompress()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' uncompress", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'uncompress'", (string) $pdf->getCommand());
     }
 
     public function testCanKeepFirstId()
@@ -472,7 +475,7 @@ public function testCanKeepFirstId()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' keep_first_id", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'keep_first_id'", (string) $pdf->getCommand());
     }
 
     public function testCanKeepFinalId()
@@ -486,7 +489,7 @@ public function testCanKeepFinalId()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' keep_final_id", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'keep_final_id'", (string) $pdf->getCommand());
     }
 
     public function testCanDropXfa()
@@ -500,7 +503,7 @@ public function testCanDropXfa()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' drop_xfa", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'drop_xfa'", (string) $pdf->getCommand());
     }
 
     public function testCanSetPasswords()
@@ -515,7 +518,7 @@ public function testCanSetPasswords()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' owner_pw '\"'\''**' user_pw '**\"'\'''", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'owner_pw' '\"'\''**' 'user_pw' '**\"'\'''", (string) $pdf->getCommand());
     }
 
     public function testSet128BitEncryption()
@@ -529,7 +532,7 @@ public function testSet128BitEncryption()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' encrypt_128bit", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'encrypt_128bit'", (string) $pdf->getCommand());
     }
 
     public function testSet40BitEncryption()
@@ -543,7 +546,7 @@ public function testSet40BitEncryption()
         $this->assertFileExists($file);
 
         $tmpFile = (string) $pdf->getTmpFile();
-        $this->assertEquals("pdftk A='$document' output '$tmpFile' encrypt_40bit", (string) $pdf->getCommand());
+        $this->assertEquals("pdftk 'A'='$document' 'output' '$tmpFile' 'encrypt_40bit'", (string) $pdf->getCommand());
     }
 
 
@@ -653,7 +656,7 @@ protected function getOutFile()
 PageMediaRect: 0 0 595 842
 PageMediaDimensions: 595 842
 EOD;
-    
+
     protected $formDataArray = array(
         "Info" => array(
             "CreationDate" => "D:20140709121536+02'00'",
@@ -695,7 +698,7 @@ protected function getOutFile()
                 "Dimensions" => "595 842"
             ),
         )
-        
+
     );
 
     protected $formDataFields = <<<EOD
diff --git a/tests/XfdfFileTest.php b/tests/XfdfFileTest.php
index 699605a..b881d50 100644
--- a/tests/XfdfFileTest.php
+++ b/tests/XfdfFileTest.php
@@ -1,7 +1,10 @@
 <?php
+namespace tests;
+
+use PHPUnit\Framework\TestCase;
 use mikehaertl\pdftk\XfdfFile;
 
-class XfdfFileTest extends \PHPUnit\Framework\TestCase
+class XfdfFileTest extends TestCase
 {
     public function testXfdfFileCreation()
     {