diff --git a/.travis.yml b/.travis.yml
index b05fe95..3929175 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,10 +4,9 @@ cache:
   directories:
     - $HOME/.composer/cache
 php:
+  - 7.3
   - 7.2
   - 7.1
-  - 7.0
-  - 5.6
 install:
   - composer self-update
   - composer install --prefer-dist
diff --git a/README.md b/README.md
index 870ee7f..12b0b6d 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ PHP library which will retrieve a thumbnail for any given URL, if available.
 
 Mandatory:
 
-  - PHP 5.6
+  - PHP 7.1 (`v2.0.0`+) - PHP 5.6 (`v1.x.x`)
   - PHP GD extension
   
 (Highly) Recommended:
diff --git a/composer.json b/composer.json
index ca906c7..5445536 100644
--- a/composer.json
+++ b/composer.json
@@ -10,11 +10,11 @@
     }
   ],
   "require": {
-    "php": ">=5.6",
+    "php": ">=7.1",
     "phpunit/php-text-template": "^1.2"
   },
   "require-dev": {
-    "phpunit/phpunit": "^5.0 || ^6.0 || ^7.0 || ^8.0",
+    "phpunit/phpunit": "^7.0 || ^8.0",
     "php-coveralls/php-coveralls": "^2.0",
     "squizlabs/php_codesniffer": "^3.0"
   },
diff --git a/tests/WebThumbnailer/Application/CacheManagerTest.php b/tests/WebThumbnailer/Application/CacheManagerTest.php
index 6dfb20b..2eb3804 100644
--- a/tests/WebThumbnailer/Application/CacheManagerTest.php
+++ b/tests/WebThumbnailer/Application/CacheManagerTest.php
@@ -2,6 +2,7 @@
 
 namespace WebThumbnailer\Application;
 
+use PHPUnit\Framework\TestCase;
 use WebThumbnailer\Utils\FileUtils;
 
 /**
@@ -11,7 +12,7 @@
  *
  * @package WebThumbnailer\Application
  */
-class CacheManagerTest extends \PHPUnit_Framework_TestCase
+class CacheManagerTest extends TestCase
 {
     /**
      * @var string $cache relative path.
@@ -21,7 +22,7 @@ class CacheManagerTest extends \PHPUnit_Framework_TestCase
     /**
      * Load test config before running tests.
      */
-    public function setUp()
+    public function setUp(): void
     {
         $resource = 'tests/WebThumbnailer/resources/';
         ConfigManager::$configFiles = [$resource . 'settings-useful.json'];
@@ -31,7 +32,7 @@ public function setUp()
     /**
      * Remove cache folder after every tests.
      */
-    public function tearDown()
+    public function tearDown(): void
     {
         FileUtils::rmdir(ConfigManager::get('settings.path.cache'));
     }
@@ -43,32 +44,29 @@ public function testGetCachePathValid()
     {
         $path = CacheManager::getCachePath(CacheManager::TYPE_THUMB);
         $this->assertTrue(is_dir($path));
-        $this->assertContains(self::$cache . CacheManager::TYPE_THUMB .'/', $path);
+        $this->assertStringContainsString(self::$cache . CacheManager::TYPE_THUMB .'/', $path);
         $path = CacheManager::getCachePath(CacheManager::TYPE_FINDER);
         $this->assertTrue(is_dir($path));
-        $this->assertContains(self::$cache . CacheManager::TYPE_FINDER .'/', $path);
+        $this->assertStringContainsString(self::$cache . CacheManager::TYPE_FINDER .'/', $path);
     }
 
     /**
      * Test getCachePath() with an invalid type.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessageRegExp /Unknown cache type/
      */
     public function testGetCachePathInvalidType()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessageRegExp('/Unknown cache type/');
         CacheManager::getCachePath('nope');
     }
 
     /**
      * Test getCachePath() without cache folder.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessageRegExp /Cache folders are not writable/
-     *
      */
     public function testGetCachePathNoFolder()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessageRegExp('/Cache folders are not writable/');
         CacheManager::getCachePath(CacheManager::TYPE_THUMB, true);
     }
 
@@ -85,9 +83,9 @@ public function testGetCacheFilePathValid()
         $cacheFile = CacheManager::getCacheFilePath($url, $domain, $type, $width, $height, false);
         $whateverDir = self::$cache . 'thumb/'. md5($domain) .'/';
         $this->assertTrue(is_dir($whateverDir));
-        $this->assertContains($whateverDir, $cacheFile);
+        $this->assertStringContainsString($whateverDir, $cacheFile);
         // sha1 sum + dimensions
-        $this->assertContains('0a35602901944a0c6d853da2a5364665c2bda069' . '51200' . '.jpg', $cacheFile);
+        $this->assertStringContainsString('0a35602901944a0c6d853da2a5364665c2bda069' . '51200' . '.jpg', $cacheFile);
     }
 
     /**
diff --git a/tests/WebThumbnailer/Application/ConfigManagerTest.php b/tests/WebThumbnailer/Application/ConfigManagerTest.php
index 4938d2b..6506e70 100644
--- a/tests/WebThumbnailer/Application/ConfigManagerTest.php
+++ b/tests/WebThumbnailer/Application/ConfigManagerTest.php
@@ -2,6 +2,7 @@
 
 namespace WebThumbnailer\Application;
 
+use PHPUnit\Framework\TestCase;
 use WebThumbnailer\Utils\DataUtils;
 use WebThumbnailer\Utils\FileUtils;
 
@@ -12,12 +13,12 @@
  *
  * @package WebThumbnailer\Application
  */
-class ConfigManagerTest extends \PHPUnit_Framework_TestCase
+class ConfigManagerTest extends TestCase
 {
     /**
      * Before each test method.
      */
-    public function setUp()
+    public function setUp(): void
     {
         ConfigManager::$configFiles = [];
         ConfigManager::reload();
diff --git a/tests/WebThumbnailer/Application/ThumbnailerTest.php b/tests/WebThumbnailer/Application/ThumbnailerTest.php
index b898149..e588eb6 100644
--- a/tests/WebThumbnailer/Application/ThumbnailerTest.php
+++ b/tests/WebThumbnailer/Application/ThumbnailerTest.php
@@ -2,6 +2,8 @@
 
 namespace WebThumbnailer\Application;
 
+use PHPUnit\Framework\TestCase;
+use WebThumbnailer\Exception\BadRulesException;
 use WebThumbnailer\Utils\FileUtils;
 use WebThumbnailer\Utils\SizeUtils;
 use WebThumbnailer\WebThumbnailer;
@@ -13,7 +15,7 @@
  *
  * @package WebThumbnailer\Application
  */
-class ThumbnailerTest extends \PHPUnit_Framework_TestCase
+class ThumbnailerTest extends TestCase
 {
     /**
      * @var string Gravatar image link.
@@ -25,7 +27,7 @@ class ThumbnailerTest extends \PHPUnit_Framework_TestCase
      */
     public static $gravatarThumb = 'http://gravatar.com/avatar/69ae657aa40c6c777aa2f391a63f327f?s=320';
 
-    public function setUp()
+    public function setUp(): void
     {
         FileUtils::rmdir(__DIR__ .'/../../../cache/finder');
         FileUtils::rmdir(__DIR__ .'/../../../cache/thumb');
@@ -184,12 +186,11 @@ public function testDownloadSizedThumbnailWidth()
 
     /**
      * Try to create an instance of Thumbnailer with incompatible settings.
-     *
-     * @expectedException WebThumbnailer\Exception\BadRulesException
-     * @expectedExceptionMessageRegExp /Only one of these flags can be set between: DOWNLOAD HOTLINK HOTLINK_STRICT/
      */
     public function testDownloadBadConfigurationDownload()
     {
+        $this->expectException(BadRulesException::class);
+        $this->expectExceptionMessageRegExp('/Only one of these flags can be set between: DOWNLOAD HOTLINK HOTLINK_STRICT/');
         $options = [
             WebThumbnailer::DOWNLOAD,
             WebThumbnailer::HOTLINK_STRICT,
diff --git a/tests/WebThumbnailer/Finder/DefaultFinderTest.php b/tests/WebThumbnailer/Finder/DefaultFinderTest.php
index 7ae5acd..87bdf90 100644
--- a/tests/WebThumbnailer/Finder/DefaultFinderTest.php
+++ b/tests/WebThumbnailer/Finder/DefaultFinderTest.php
@@ -2,6 +2,7 @@
 
 namespace WebThumbnailer\Finder;
 
+use PHPUnit\Framework\TestCase;
 use WebThumbnailer\WebThumbnailer;
 
 /**
@@ -9,7 +10,7 @@
  *
  * @package WebThumbnailer\Finder
  */
-class DefaultFinderTest extends \PHPUnit_Framework_TestCase
+class DefaultFinderTest extends TestCase
 {
     /**
      * PHP builtin local server URL.
diff --git a/tests/WebThumbnailer/Finder/FinderFactoryTest.php b/tests/WebThumbnailer/Finder/FinderFactoryTest.php
index 3c7f6bb..d1cecb4 100644
--- a/tests/WebThumbnailer/Finder/FinderFactoryTest.php
+++ b/tests/WebThumbnailer/Finder/FinderFactoryTest.php
@@ -2,12 +2,15 @@
 
 namespace WebThumbnailer\Finder;
 
+use PHPUnit\Framework\TestCase;
+use WebThumbnailer\Exception\BadRulesException;
+
 /**
  * Class FinderFactoryTest
  *
  * @package WebThumbnailer\Finder
  */
-class FinderFactoryTest extends \PHPUnit_Framework_TestCase
+class FinderFactoryTest extends TestCase
 {
     /**
      * Test getFinder() with a supported domain.
@@ -178,6 +181,7 @@ public function testGetThumbnailMetaGravatar()
      */
     public function testCheckMetaFormatValid()
     {
+        $this->addToAssertionCount(1);
         $meta = [
             'finder' => 'foo',
             'domains' => ['bar']
@@ -189,11 +193,10 @@ public function testCheckMetaFormatValid()
 
     /**
      * Test checkMetaFormat() with invalid info.
-     *
-     * @expectedException \WebThumbnailer\Exception\BadRulesException
      */
     public function testCheckMetaFormatBadRules()
     {
+        $this->expectException(BadRulesException::class);
         $meta = array('finder' => 'test');
         FinderFactory::checkMetaFormat($meta);
     }
diff --git a/tests/WebThumbnailer/Finder/FlickRFinderTest.php b/tests/WebThumbnailer/Finder/FlickRFinderTest.php
index e7e2158..ca25971 100644
--- a/tests/WebThumbnailer/Finder/FlickRFinderTest.php
+++ b/tests/WebThumbnailer/Finder/FlickRFinderTest.php
@@ -2,12 +2,14 @@
 
 namespace WebThumbnailer\Finder;
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * Class FlickRFinderTest
  *
  * @package WebThumbnailer\Finder
  */
-class FlickRFinderTest extends \PHPUnit_Framework_TestCase
+class FlickRFinderTest extends TestCase
 {
     /**
      * @var array Finder rules.
@@ -22,7 +24,7 @@ class FlickRFinderTest extends \PHPUnit_Framework_TestCase
     /**
      * Before every tests, reset rules and params.
      */
-    public function setUp()
+    public function setUp(): void
     {
         self::$rules  = [
             'image_regex' => '<meta property=\"og:image\" content=\"(.*?)\"',
diff --git a/tests/WebThumbnailer/Finder/QueryRegexFinderTest.php b/tests/WebThumbnailer/Finder/QueryRegexFinderTest.php
index 9eab0b8..a83b378 100644
--- a/tests/WebThumbnailer/Finder/QueryRegexFinderTest.php
+++ b/tests/WebThumbnailer/Finder/QueryRegexFinderTest.php
@@ -2,6 +2,8 @@
 
 namespace WebThumbnailer\Finder;
 
+use PHPUnit\Framework\TestCase;
+use WebThumbnailer\Exception\BadRulesException;
 use WebThumbnailer\Utils\DataUtils;
 use WebThumbnailer\Utils\FileUtils;
 
@@ -10,7 +12,7 @@
  *
  * @package WebThumbnailer\Finder
  */
-class QueryRegexFinderTest extends \PHPUnit_Framework_TestCase
+class QueryRegexFinderTest extends TestCase
 {
     /**
      * @var array Finder rules.
@@ -25,7 +27,7 @@ class QueryRegexFinderTest extends \PHPUnit_Framework_TestCase
     /**
      * Before every tests, reset rules and params.
      */
-    public function setUp()
+    public function setUp(): void
     {
         self::$rules  = [
             'image_regex' => '<img class="thumb" src="(.*?)" alt="(.*?)">',
@@ -164,22 +166,20 @@ public function testGetName()
 
     /**
      * Test loading the finder with bad rules (`thumbnail_url`).
-     *
-     * @expectedException \WebThumbnailer\Exception\BadRulesException
      */
     public function testQueryRegexFinderBadRulesThumbUrl()
     {
+        $this->expectException(BadRulesException::class);
         unset(self::$rules['thumbnail_url']);
         new QueryRegexFinder('domain.tld', '', self::$rules, null);
     }
 
     /**
      * Test loading the finder with bad rules (`image_regex`).
-     *
-     * @expectedException \WebThumbnailer\Exception\BadRulesException
      */
     public function testQueryRegexFinderBadRulesImageRegex()
     {
+        $this->expectException(BadRulesException::class);
         unset(self::$rules['image_regex']);
         new QueryRegexFinder('domain.tld', '', self::$rules, null);
     }
@@ -217,12 +217,12 @@ public function testQueryRegexNoEnoughMatch()
 
     /**
      * Use an unknown option in the URL.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessage Unknown option "option" for the finder "Query Regex"
      */
     public function testQueryRegexUnknownOption()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Unknown option "option" for the finder "Query Regex"');
+
         $url = __DIR__ . '/../resources/queryregex/one-thumb.html';
         self::$rules['thumbnail_url'] = '${option}';
         $finder = new QueryRegexFinder('domain.tld', $url, self::$rules, null);
diff --git a/tests/WebThumbnailer/Finder/UrlRegexFinderTest.php b/tests/WebThumbnailer/Finder/UrlRegexFinderTest.php
index 4bcd27a..944a3f6 100644
--- a/tests/WebThumbnailer/Finder/UrlRegexFinderTest.php
+++ b/tests/WebThumbnailer/Finder/UrlRegexFinderTest.php
@@ -2,6 +2,8 @@
 
 namespace WebThumbnailer\Finder;
 
+use PHPUnit\Framework\TestCase;
+use WebThumbnailer\Exception\BadRulesException;
 use WebThumbnailer\Utils\DataUtils;
 use WebThumbnailer\Utils\FileUtils;
 use WebThumbnailer\WebThumbnailer;
@@ -11,13 +13,15 @@
  *
  * @package WebThumbnailer\Finder
  */
-class UrlRegexFinderTest extends \PHPUnit_Framework_TestCase
+class UrlRegexFinderTest extends TestCase
 {
     /**
      * Test checkRules() with valid data.
      */
     public function testCheckRulesValid()
     {
+        $this->addToAssertionCount(1);
+
         $rules = array(
             'url_regex' => 'str',
             'thumbnail_url' => 'str',
@@ -28,11 +32,11 @@ public function testCheckRulesValid()
 
     /**
      * Test checkRules() with invalid data.
-     *
-     * @expectedException \WebThumbnailer\Exception\BadRulesException
      */
     public function testCheckRulesMissingThumbUrl()
     {
+        $this->expectException(BadRulesException::class);
+
         $rules = [
             'url_regex' => 'str',
         ];
@@ -42,11 +46,11 @@ public function testCheckRulesMissingThumbUrl()
 
     /**
      * Test checkRules() with invalid data.
-     *
-     * @expectedException \WebThumbnailer\Exception\BadRulesException
      */
     public function testCheckRulesMissingUrlRegex()
     {
+        $this->expectException(BadRulesException::class);
+
         $rules = [
             'thumbnail_url' => 'str',
         ];
@@ -241,12 +245,12 @@ public function testFindWithDefaultOptionsBadValues()
     /**
      * Test find() with basic replacements, and default options
      * but without defining default values.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessageRegExp /No default set for option/
      */
     public function testFindWithDefaultOptionsNoDefault()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessageRegExp('/No default set for option/');
+
         $url = 'http://test.io/?123';
         $rules = array(
             'url_regex' => '/\\?([^&]+)',
@@ -264,12 +268,12 @@ public function testFindWithDefaultOptionsNoDefault()
     /**
      * Test find() with basic replacements, and default options
      * with an invalid default option.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessageRegExp /No default parameter set for option/
      */
     public function testFindWithDefaultOptionsNoDefaultParam()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessageRegExp('/No default parameter set for option/');
+
         $url = 'http://test.io/?123';
         $rules = array(
             'url_regex' => '/\\?([^&]+)',
@@ -288,12 +292,12 @@ public function testFindWithDefaultOptionsNoDefaultParam()
 
     /**
      * Test find() with basic replacements, and options not matching anything.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessageRegExp /Unknown option/
      */
     public function testFindWithDefaultOptionsUnknownOption()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessageRegExp('/Unknown option/');
+
         $url = 'http://test.io/?123';
         $rules = array(
             'url_regex' => '/\\?([^&]+)',
diff --git a/tests/WebThumbnailer/Utils/DataUtilsTest.php b/tests/WebThumbnailer/Utils/DataUtilsTest.php
index 6c8dd66..7a8c96f 100644
--- a/tests/WebThumbnailer/Utils/DataUtilsTest.php
+++ b/tests/WebThumbnailer/Utils/DataUtilsTest.php
@@ -2,6 +2,8 @@
 
 namespace WebThumbnailer\Utils;
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * Class DataUtilsTest
  *
@@ -9,7 +11,7 @@
  *
  * @package WebThumbnailer\Utils
  */
-class DataUtilsTest extends \PHPUnit_Framework_TestCase
+class DataUtilsTest extends TestCase
 {
     public function testLoadJsonResource()
     {
@@ -18,21 +20,17 @@ public function testLoadJsonResource()
         $this->assertEquals('medium', $rules['imgur_single']['options']['size']['default']);
     }
 
-    /**
-     * @expectedException \Exception
-     * @expectedExceptionMessage JSON resource file not found or not readable.
-     */
     public function testLoadJsonResourceNoFile()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('JSON resource file not found or not readable.');
         DataUtils::loadJson(FileUtils::RESOURCES_PATH . 'nope.json');
     }
 
-    /**
-     * @expectedException \Exception
-     * @expectedExceptionMessageRegExp /An error occured while parsing JSON file: error code #/
-     */
     public function testLoadJsonResourceBadSyntax()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessageRegExp('/An error occured while parsing JSON file: error code #/');
         $path = __DIR__ . DIRECTORY_SEPARATOR . '..'. DIRECTORY_SEPARATOR . 'resources' . DIRECTORY_SEPARATOR;
         DataUtils::loadJson($path . 'badsyntax.json');
     }
diff --git a/tests/WebThumbnailer/Utils/FileUtilsTests.php b/tests/WebThumbnailer/Utils/FileUtilsTests.php
index 5486977..9e70830 100644
--- a/tests/WebThumbnailer/Utils/FileUtilsTests.php
+++ b/tests/WebThumbnailer/Utils/FileUtilsTests.php
@@ -2,12 +2,14 @@
 
 namespace WebThumbnailer\Utils;
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * Class FileUtilsTests
  *
  * @package WebThumbnailer\Utils
  */
-class FileUtilsTests extends \PHPUnit_Framework_TestCase
+class FileUtilsTests extends TestCase
 {
     /**
      * Test getPath() with a valid path.
diff --git a/tests/WebThumbnailer/Utils/FinderUtilsTest.php b/tests/WebThumbnailer/Utils/FinderUtilsTest.php
index fb15b15..cd029a5 100644
--- a/tests/WebThumbnailer/Utils/FinderUtilsTest.php
+++ b/tests/WebThumbnailer/Utils/FinderUtilsTest.php
@@ -2,12 +2,14 @@
 
 namespace WebThumbnailer\Utils;
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * Class FinderUtilsTest
  *
  * @package WebThumbnailer\utils
  */
-class FinderUtilsTest extends \PHPUnit_Framework_TestCase
+class FinderUtilsTest extends TestCase
 {
     /**
      * Test buildRegex() function.
diff --git a/tests/WebThumbnailer/Utils/ImageUtilsTest.php b/tests/WebThumbnailer/Utils/ImageUtilsTest.php
index 938ad21..a454626 100644
--- a/tests/WebThumbnailer/Utils/ImageUtilsTest.php
+++ b/tests/WebThumbnailer/Utils/ImageUtilsTest.php
@@ -2,6 +2,9 @@
 
 namespace WebThumbnailer\Utils;
 
+use PHPUnit\Framework\TestCase;
+use WebThumbnailer\Exception\NotAnImageException;
+
 /**
  * Class ImageUtilsTest
  *
@@ -9,7 +12,7 @@
  *
  * @package WebThumbnailer\utils
  */
-class ImageUtilsTest extends \PHPUnit_Framework_TestCase
+class ImageUtilsTest extends TestCase
 {
     /**
      * @var string Image as string.
@@ -24,7 +27,7 @@ class ImageUtilsTest extends \PHPUnit_Framework_TestCase
     /**
      * Regenerate the image before every tests.
      */
-    public function setUp()
+    public function setUp(): void
     {
         // From http://php.net/imagecreatefromstring
         $data = 'iVBORw0KGgoAAAANSUhEUgAAABwAAAASCAMAAAB/2U7WAAAABl'
@@ -38,7 +41,7 @@ public function setUp()
      * Remove the test image in workdir after every test.
      * Ignore errors.
      */
-    public function tearDown()
+    public function tearDown(): void
     {
         @unlink(self::$WORKDIR . 'file1.png');
     }
@@ -87,47 +90,47 @@ public function testGenerateThumbnail()
 
     /**
      * Generate a thumbnail into a non existent folder => Exception.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessage Target file is not writable.
      */
     public function testGenerateThumbnailUnwritable()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Target file is not writable.');
+
         $path = self::$WORKDIR . 'nope' . DIRECTORY_SEPARATOR . 'file';
         @ImageUtils::generateThumbnail(self::$imageSource, $path, 28, 18);
     }
 
     /**
      * Generate a thumbnail from a string which is not an image => NotAnImageException.
-     *
-     * @expectedException \WebThumbnailer\Exception\NotAnImageException
      */
     public function testGenerateThumbnailNotAnImage()
     {
+        $this->expectException(NotAnImageException::class);
+
         $path = self::$WORKDIR . 'file1.png';
         ImageUtils::generateThumbnail('virus.exe', $path, 28, 18);
     }
 
     /**
      * Generate a thumbnail with bad sizes => Exception.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessage Could not generate the thumbnail from source image.
      */
     public function testGenerateThumbnailBadSize()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Could not generate the thumbnail from source image.');
+
         $path = self::$WORKDIR . 'file1.png';
         @ImageUtils::generateThumbnail(self::$imageSource, $path, -1, -1);
     }
 
     /**
      * Generate a thumbnail with bad sizes (Double 0) => Exception.
-     *
-     * @expectedException \Exception
-     * @expectedExceptionMessage At least maxwidth or maxheight needs to be defined.
      */
     public function testGenerateThumbnailBadSizeDoubleZero()
     {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('At least maxwidth or maxheight needs to be defined.');
+
         $path = self::$WORKDIR . 'file1.png';
         @ImageUtils::generateThumbnail(self::$imageSource, $path, 0, 0);
     }
diff --git a/tests/WebThumbnailer/Utils/UrlUtilsTest.php b/tests/WebThumbnailer/Utils/UrlUtilsTest.php
index 3023335..8a5fa67 100644
--- a/tests/WebThumbnailer/Utils/UrlUtilsTest.php
+++ b/tests/WebThumbnailer/Utils/UrlUtilsTest.php
@@ -2,6 +2,8 @@
 
 namespace WebThumbnailer\Utils;
 
+use PHPUnit\Framework\TestCase;
+
 /**
  * Class UrlUtilsTest
  *
@@ -9,7 +11,7 @@
  *
  * @package WebThumbnailer\Utils
  */
-class UrlUtilsTest extends \PHPUnit_Framework_TestCase
+class UrlUtilsTest extends TestCase
 {
     /**
      * Test getDomain() from various URL.
diff --git a/tests/WebThumbnailer/WebThumbnailerTest.php b/tests/WebThumbnailer/WebThumbnailerTest.php
index 3e0cb0f..a52ed1d 100644
--- a/tests/WebThumbnailer/WebThumbnailerTest.php
+++ b/tests/WebThumbnailer/WebThumbnailerTest.php
@@ -2,6 +2,7 @@
 
 namespace WebThumbnailer;
 
+use PHPUnit\Framework\TestCase;
 use WebThumbnailer\Application\ConfigManager;
 use WebThumbnailer\Utils\FileUtils;
 
@@ -12,7 +13,7 @@
  *
  * @package WebThumbnailer
  */
-class WebThumbnailerTest extends \PHPUnit_Framework_TestCase
+class WebThumbnailerTest extends TestCase
 {
     /**
      * PHP builtin local server URL.
@@ -42,7 +43,7 @@ class WebThumbnailerTest extends \PHPUnit_Framework_TestCase
     /**
      * Load test config before running tests.
      */
-    public function setUp()
+    public function setUp(): void
     {
         $resource = 'tests/WebThumbnailer/resources/';
         ConfigManager::clear();
@@ -52,7 +53,7 @@ public function setUp()
     /**
      * Remove cache folder after every tests.
      */
-    public function tearDown()
+    public function tearDown(): void
     {
         FileUtils::rmdir(self::$cache);
         FileUtils::rmdir(self::$tmp);