diff --git a/.gitignore b/.gitignore
index 4a118e9..843b036 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 composer.lock
 !composer.json
 vendor
+build
diff --git a/.travis.yml b/.travis.yml
index df8de84..cb6be7f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,13 +1,11 @@
 language: php
 php:
-  - 5.5
   - 5.6
   - 7.0
   - 7.1
   - nightly
 matrix:
   allow_failures:
-    - php: 5.5
     - php: 5.6
     - php: nightly
   fast_finish: true
diff --git a/composer.json b/composer.json
index f67cfd6..ce5e4e0 100644
--- a/composer.json
+++ b/composer.json
@@ -20,9 +20,9 @@
         "classmap": ["src/"]
     },
     "require": {
-        "php": ">=5.2.0"
+        "php": ">=5.6.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.7"
+        "phpunit/phpunit": "^5.7 || ^6.3"
     }
-}
\ No newline at end of file
+}
diff --git a/phpunit.xml b/phpunit.xml
index e7d521e..06a0c56 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -13,7 +13,7 @@
 >
     <testsuites>
         <testsuite name="Test Suite">
-            <directory>./tests/</directory>
+            <directory suffix="Test.php" phpVersion="5.6.0" phpVersionOperator=">=">./tests</directory>
         </testsuite>
     </testsuites>
 
@@ -22,4 +22,4 @@
             <directory>./src/</directory>
         </whitelist>
     </filter>
-</phpunit>
\ No newline at end of file
+</phpunit>
diff --git a/tests/PaletteTests.php b/tests/PaletteTest.php
similarity index 87%
rename from tests/PaletteTests.php
rename to tests/PaletteTest.php
index 012c7b0..54fe5f5 100644
--- a/tests/PaletteTests.php
+++ b/tests/PaletteTest.php
@@ -1,6 +1,6 @@
 <?php
 
-class PaletteTests extends \PHPUnit_Framework_TestCase
+class PaletteTest extends \PHPUnit_Framework_TestCase
 {
     public function test_class_is_found_and_has_default_attributes()
     {
@@ -16,7 +16,7 @@ class PaletteTests extends \PHPUnit_Framework_TestCase
 
     public function test_known_images()
     {
-        $location = dirname(__FILE__) . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR;
+        $location = __DIR__ . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR;
         $images = ['black.png' => '000000', 'red.png' => 'CC3333'];
 
         foreach ($images as $imageFile => $hex) {
@@ -29,4 +29,4 @@ class PaletteTests extends \PHPUnit_Framework_TestCase
             $this->assertEquals($image, $palette->filename);            
         }
     }
-}
\ No newline at end of file
+}