diff --git a/.atoum.php b/.atoum.php
new file mode 100644
index 0000000..3d84643
--- /dev/null
+++ b/.atoum.php
@@ -0,0 +1,30 @@
+<?php
+use mageekguy\atoum\reports;
+
+$runner
+    ->addTestsFromDirectory(__DIR__ . '/tests/units');
+
+$runner->getScore()->getCoverage()->excludeDirectory(__DIR__ . '/tests/units/mock');
+
+$travis = getenv('TRAVIS');
+if ($travis) {
+    $script->addDefaultReport();
+    $coverallsToken = getenv('COVERALLS_REPO_TOKEN');
+    if ($coverallsToken) {
+        $coverallsReport = new reports\asynchronous\coveralls('classes', $coverallsToken);
+        $defaultFinder = $coverallsReport->getBranchFinder();
+        $coverallsReport
+            ->setBranchFinder(function () use ($defaultFinder) {
+                if (($branch = getenv('TRAVIS_BRANCH')) === false) {
+                    $branch = $defaultFinder();
+                }
+                return $branch;
+            }
+            )
+            ->setServiceName('travis-ci')
+            ->setServiceJobId(getenv('TRAVIS_JOB_ID'))
+            ->addDefaultWriter()
+        ;
+        $runner->addReport($coverallsReport);
+    }
+}
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..47f4af2
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,9 @@
+language: php
+php:
+  - 7.1
+  - 7.2
+  - 7.3
+  - 7.4
+install:
+  - composer install
+script: composer test
diff --git a/composer.json b/composer.json
index 58ccc06..891466d 100644
--- a/composer.json
+++ b/composer.json
@@ -30,5 +30,8 @@
         "psr-4": {
             "ByJoby\\ImageTransform\\tests\\": "tests/"
         }
+    },
+    "scripts": {
+        "test": "./vendor/bin/atoum -d tests"
     }
 }
diff --git a/tests/units/100x200.jpg b/tests/units/100x200.jpg
new file mode 100644
index 0000000..aa3bcc5
Binary files /dev/null and b/tests/units/100x200.jpg differ
diff --git a/tests/units/200x100.jpg b/tests/units/200x100.jpg
new file mode 100644
index 0000000..cb9088b
Binary files /dev/null and b/tests/units/200x100.jpg differ
diff --git a/tests/units/200x200.jpg b/tests/units/200x200.jpg
new file mode 100644
index 0000000..6a4cf3e
Binary files /dev/null and b/tests/units/200x200.jpg differ
diff --git a/tests/units/Sizers/Cover.php b/tests/units/Sizers/Cover.php
index ba9f46e..cb54cf2 100644
--- a/tests/units/Sizers/Cover.php
+++ b/tests/units/Sizers/Cover.php
@@ -3,8 +3,171 @@
 namespace ByJoby\ImageTransform\tests\units\Sizers;
 
 use atoum;
+use ByJoby\ImageTransform\Sizers\Cover as SizerUnderTest;
+use ByJoby\ImageTransform\tests\units\mock\MockDriver;
 
 class Cover extends atoum
 {
-    
+    public function testPortraitWhenImageIsTaller()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../100x200.jpg',100,150))
+            ->integer($image->width())->isEqualTo(100)
+            ->integer($image->height())->isEqualTo(200)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(100)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(200)
+            ->variable($image->sizer()->cropToWidth())->isEqualTo(100)
+            ->variable($image->sizer()->cropToHeight())->isEqualTo(150)
+            ->given($image->rotate())
+                ->integer($image->width())->isEqualTo(300)
+                ->integer($image->height())->isEqualTo(150)
+                ->variable($image->sizer()->resizeToWidth())->isEqualTo(300)
+                ->variable($image->sizer()->resizeToHeight())->isEqualTo(150)
+                ->variable($image->sizer()->cropToWidth())->isEqualTo(100)
+                ->variable($image->sizer()->cropToHeight())->isEqualTo(150)
+        ;
+    }
+
+    // public function testPortraitWhenImageIsShorter()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../100x200.jpg',50,300))
+    //         ->integer($image->width())->isEqualTo(50)
+    //         ->integer($image->height())->isEqualTo(100)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(50)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(100)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //         ->given($image->rotate())
+    //             ->integer($image->width())->isEqualTo(50)
+    //             ->integer($image->height())->isEqualTo(25)
+    //             ->variable($image->sizer()->resizeToWidth())->isEqualTo(50)
+    //             ->variable($image->sizer()->resizeToHeight())->isEqualTo(25)
+    //             ->variable($image->sizer()->cropToWidth())->isNull()
+    //             ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testPortraitWithSquareImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x200.jpg',75,300))
+    //         ->integer($image->width())->isEqualTo(75)
+    //         ->integer($image->height())->isEqualTo(75)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(75)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testPortraitWithLandscapeImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x100.jpg',100,200))
+    //         ->integer($image->width())->isEqualTo(100)
+    //         ->integer($image->height())->isEqualTo(50)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(100)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(50)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testLandscapeWhenImageIsTaller()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x100.jpg',150,100))
+    //         ->integer($image->width())->isEqualTo(150)
+    //         ->integer($image->height())->isEqualTo(75)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(150)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testLandscapeWhenImageIsShorter()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x100.jpg',300,75))
+    //         ->integer($image->width())->isEqualTo(150)
+    //         ->integer($image->height())->isEqualTo(75)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(150)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testLandscapeWithSquareImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x200.jpg',300,75))
+    //         ->integer($image->width())->isEqualTo(75)
+    //         ->integer($image->height())->isEqualTo(75)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(75)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testLandscapeWithPortraitImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../100x200.jpg',200,100))
+    //         ->integer($image->width())->isEqualTo(50)
+    //         ->integer($image->height())->isEqualTo(100)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(50)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(100)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testWithSmallSquareImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x200.jpg',300,300))
+    //         ->integer($image->width())->isEqualTo(300)
+    //         ->integer($image->height())->isEqualTo(300)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(300)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(300)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testWithSmallLandscapeImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../200x100.jpg',300,300))
+    //         ->integer($image->width())->isEqualTo(300)
+    //         ->integer($image->height())->isEqualTo(150)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(300)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(150)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    // public function testWithSmallPortraitImage()
+    // {
+    //     $this
+    //         ->given($image = $this->image(__DIR__.'/../100x200.jpg',300,300))
+    //         ->integer($image->width())->isEqualTo(150)
+    //         ->integer($image->height())->isEqualTo(300)
+    //         ->variable($image->sizer()->resizeToWidth())->isEqualTo(150)
+    //         ->variable($image->sizer()->resizeToHeight())->isEqualTo(300)
+    //         ->variable($image->sizer()->cropToWidth())->isNull()
+    //         ->variable($image->sizer()->cropToHeight())->isNull()
+    //     ;
+    // }
+
+    protected function image(string $path, int $width, int $height)
+    {
+        $driver = new MockDriver();
+        return $driver->image($path, new SizerUnderTest($width, $height));
+    }
 }
diff --git a/tests/units/Sizers/Fit.php b/tests/units/Sizers/Fit.php
new file mode 100644
index 0000000..d8f9865
--- /dev/null
+++ b/tests/units/Sizers/Fit.php
@@ -0,0 +1,173 @@
+<?php
+/* image-transform | https://github.com/jobyone/image-transform | MIT License */
+namespace ByJoby\ImageTransform\tests\units\Sizers;
+
+use atoum;
+use ByJoby\ImageTransform\Sizers\Fit as SizerUnderTest;
+use ByJoby\ImageTransform\tests\units\mock\MockDriver;
+
+class Fit extends atoum
+{
+    public function testPortraitWhenImageIsTaller()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../100x200.jpg',100,150))
+            ->integer($image->width())->isEqualTo(75)
+            ->integer($image->height())->isEqualTo(150)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(150)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+            ->given($image->rotate())
+                ->integer($image->width())->isEqualTo(100)
+                ->integer($image->height())->isEqualTo(50)
+                ->variable($image->sizer()->resizeToWidth())->isEqualTo(100)
+                ->variable($image->sizer()->resizeToHeight())->isEqualTo(50)
+                ->variable($image->sizer()->cropToWidth())->isNull()
+                ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testPortraitWhenImageIsShorter()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../100x200.jpg',50,300))
+            ->integer($image->width())->isEqualTo(50)
+            ->integer($image->height())->isEqualTo(100)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(50)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(100)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+            ->given($image->rotate())
+                ->integer($image->width())->isEqualTo(50)
+                ->integer($image->height())->isEqualTo(25)
+                ->variable($image->sizer()->resizeToWidth())->isEqualTo(50)
+                ->variable($image->sizer()->resizeToHeight())->isEqualTo(25)
+                ->variable($image->sizer()->cropToWidth())->isNull()
+                ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testPortraitWithSquareImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x200.jpg',75,300))
+            ->integer($image->width())->isEqualTo(75)
+            ->integer($image->height())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testPortraitWithLandscapeImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x100.jpg',100,200))
+            ->integer($image->width())->isEqualTo(100)
+            ->integer($image->height())->isEqualTo(50)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(100)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(50)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testLandscapeWhenImageIsTaller()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x100.jpg',150,100))
+            ->integer($image->width())->isEqualTo(150)
+            ->integer($image->height())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(150)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testLandscapeWhenImageIsShorter()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x100.jpg',300,75))
+            ->integer($image->width())->isEqualTo(150)
+            ->integer($image->height())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(150)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testLandscapeWithSquareImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x200.jpg',300,75))
+            ->integer($image->width())->isEqualTo(75)
+            ->integer($image->height())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(75)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(75)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testLandscapeWithPortraitImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../100x200.jpg',200,100))
+            ->integer($image->width())->isEqualTo(50)
+            ->integer($image->height())->isEqualTo(100)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(50)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(100)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testWithSmallSquareImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x200.jpg',300,300))
+            ->integer($image->width())->isEqualTo(300)
+            ->integer($image->height())->isEqualTo(300)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(300)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(300)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testWithSmallLandscapeImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../200x100.jpg',300,300))
+            ->integer($image->width())->isEqualTo(300)
+            ->integer($image->height())->isEqualTo(150)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(300)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(150)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    public function testWithSmallPortraitImage()
+    {
+        $this
+            ->given($image = $this->image(__DIR__.'/../100x200.jpg',300,300))
+            ->integer($image->width())->isEqualTo(150)
+            ->integer($image->height())->isEqualTo(300)
+            ->variable($image->sizer()->resizeToWidth())->isEqualTo(150)
+            ->variable($image->sizer()->resizeToHeight())->isEqualTo(300)
+            ->variable($image->sizer()->cropToWidth())->isNull()
+            ->variable($image->sizer()->cropToHeight())->isNull()
+        ;
+    }
+
+    protected function image(string $path, int $width, int $height)
+    {
+        $driver = new MockDriver();
+        return $driver->image($path, new SizerUnderTest($width, $height));
+    }
+}
diff --git a/tests/units/mock/MockDriver.php b/tests/units/mock/MockDriver.php
new file mode 100644
index 0000000..7883a42
--- /dev/null
+++ b/tests/units/mock/MockDriver.php
@@ -0,0 +1,9 @@
+<?php
+/* image-transform | https://github.com/jobyone/image-transform | MIT License */
+namespace ByJoby\ImageTransform\tests\units\mock;
+
+use ByJoby\ImageTransform\Drivers\AbstractDriver;
+
+class MockDriver extends AbstractDriver
+{
+}