diff --git a/tests/PhpZip/ZipTestCase.php b/tests/PhpZip/ZipTestCase.php
index d0eb595..91fd205 100644
--- a/tests/PhpZip/ZipTestCase.php
+++ b/tests/PhpZip/ZipTestCase.php
@@ -10,7 +10,6 @@ use PhpZip\Util\FilesUtil;
  */
 class ZipTestCase extends \PHPUnit_Framework_TestCase
 {
-
     /**
      * @var string
      */
@@ -27,12 +26,10 @@ class ZipTestCase extends \PHPUnit_Framework_TestCase
     {
         parent::setUp();
 
-        $id = uniqid('phpzip');
+        $id = uniqid('phpzip', true);
         $tempDir = sys_get_temp_dir() . '/phpunit-phpzip';
-        if (!is_dir($tempDir)) {
-            if (!mkdir($tempDir, 0755, true)) {
-                throw new \RuntimeException("Dir " . $tempDir . " can't created");
-            }
+        if (!is_dir($tempDir) && !mkdir($tempDir, 0755, true) && !is_dir($tempDir)) {
+            throw new \RuntimeException('Dir ' . $tempDir . " can't created");
         }
         $this->outputFilename = $tempDir . '/' . $id . '.zip';
         $this->outputDirname = $tempDir . '/' . $id;
@@ -61,23 +58,23 @@ class ZipTestCase extends \PHPUnit_Framework_TestCase
      */
     public static function assertCorrectZipArchive($filename, $password = null)
     {
-        if (DIRECTORY_SEPARATOR !== '\\' && `which unzip`) {
-            $command = "unzip";
+        if (self::existsProgram('unzip')) {
+            $command = 'unzip';
             if ($password !== null) {
-                $command .= " -P " . escapeshellarg($password);
+                $command .= ' -P ' . escapeshellarg($password);
             }
-            $command .= " -t " . escapeshellarg($filename);
+            $command .= ' -t ' . escapeshellarg($filename);
             exec($command, $output, $returnCode);
 
             $output = implode(PHP_EOL, $output);
 
             if ($password !== null && $returnCode === 81) {
-                if (`which 7z`) {
+                if (self::existsProgram('7z')) {
                     // WinZip 99-character limit
                     // @see https://sourceforge.net/p/p7zip/discussion/383044/thread/c859a2f0/
                     $password = substr($password, 0, 99);
 
-                    $command = "7z t -p" . escapeshellarg($password) . " " . escapeshellarg($filename);
+                    $command = '7z t -p' . escapeshellarg($password) . ' ' . escapeshellarg($filename);
                     exec($command, $output, $returnCode);
                     /**
                      * @var array $output
@@ -100,6 +97,19 @@ class ZipTestCase extends \PHPUnit_Framework_TestCase
         }
     }
 
+    /**
+     * @param string $program
+     * @return bool
+     */
+    private static function existsProgram($program){
+        if (DIRECTORY_SEPARATOR !== '\\') {
+            exec('which ' . escapeshellarg($program), $output, $returnCode);
+            return $returnCode === 0;
+        }
+        // false for Windows
+        return false;
+    }
+
     /**
      * Assert correct empty zip archive.
      *
@@ -107,15 +117,15 @@ class ZipTestCase extends \PHPUnit_Framework_TestCase
      */
     public static function assertCorrectEmptyZip($filename)
     {
-        if (DIRECTORY_SEPARATOR !== '\\' && `which zipinfo`) {
-            exec("zipinfo " . escapeshellarg($filename), $output, $returnCode);
+        if (self::existsProgram('zipinfo')) {
+            exec('zipinfo ' . escapeshellarg($filename), $output, $returnCode);
 
             $output = implode(PHP_EOL, $output);
 
             self::assertContains('Empty zipfile', $output);
         }
         $actualEmptyZipData = pack('VVVVVv', EndOfCentralDirectory::END_OF_CENTRAL_DIRECTORY_RECORD_SIG, 0, 0, 0, 0, 0);
-        self::assertEquals(file_get_contents($filename), $actualEmptyZipData);
+        self::assertStringEqualsFile($filename, $actualEmptyZipData);
     }
 
     /**
@@ -125,15 +135,15 @@ class ZipTestCase extends \PHPUnit_Framework_TestCase
      */
     public static function assertVerifyZipAlign($filename, $showErrors = false)
     {
-        if (DIRECTORY_SEPARATOR !== '\\' && `which zipalign`) {
-            exec("zipalign -c -v 4 " . escapeshellarg($filename), $output, $returnCode);
+        if (self::existsProgram('zipalign')) {
+            exec('zipalign -c -v 4 ' . escapeshellarg($filename), $output, $returnCode);
             if ($showErrors && $returnCode !== 0) {
                 fwrite(STDERR, implode(PHP_EOL, $output));
             }
             return $returnCode === 0;
-        } else {
-            fwrite(STDERR, 'Can not find program "zipalign" for test' . PHP_EOL);
-            return null;
         }
+
+        fwrite(STDERR, 'Can not find program "zipalign" for test' . PHP_EOL);
+        return null;
     }
 }