diff --git a/Parser/JsonParser.php b/Parser/JsonParser.php
new file mode 100644
index 0000000..000ec5c
--- /dev/null
+++ b/Parser/JsonParser.php
@@ -0,0 +1,121 @@
+<?php
+
+namespace Incenteev\ParameterHandler\Parser;
+
+class JsonParser implements ParserInterface
+{
+    /**
+     * Parses a JSON string to a PHP value.
+     *
+     * @param string $value A JSON string
+     * @param int    $flags Bitmask of JSON decode options. Currently only JSON_BIGINT_AS_STRING is supported (default is to cast large integers as floats)
+     * @param bool   $assoc When TRUE, returned objects will be converted into associative arrays.
+     * @param int    $depth User specified recursion depth.
+     *
+     * @return mixed A PHP value
+     */
+    public function parse($value, $flags = 0, $assoc = true, $depth = 512)
+    {
+        if ('' === $value) {
+            $result = array();
+        } else {
+            $result = json_decode($value, $assoc, $depth);
+            if (null === $result) {
+                $result = false;
+            }
+        }
+
+        return $result;
+    }
+
+    /**
+     * Dumps a given array of data to JSON format.
+     *
+     * @param array $data Data to dump.
+     *
+     * @return string Dumped JSON data
+     */
+    public function dump(array $data)
+    {
+        return $this->prettyPrint(json_encode($data));
+    }
+
+    /**
+     * Returns pretty printed JSON string.
+     * Custom implementation for compatibility with PHP < 5.4 and custom spacing.
+     *
+     * @param string $json         JSON data to be pretty printed
+     * @param string $spacer       Spacer used e.g. ' ' or "\t"
+     * @param int    $spacing      Multiplicand for spacer (count)
+     * @param bool   $newLineAtEof Whether to write a nl at end of file or not
+     *
+     * @return string Pretty printed JSON data
+     */
+    protected function prettyPrint($json, $spacer = ' ', $spacing = 2, $newLineAtEof = true)
+    {
+        $result          = '';
+        $level           = 0;
+        $in_quotes       = false;
+        $in_escape       = false;
+        $ends_line_level = null;
+        $json_length     = strlen($json);
+
+        for ($i = 0; $i < $json_length; ++$i) {
+            $char           = $json[$i];
+            $new_line_level = null;
+            $post           = '';
+            if ($ends_line_level !== null) {
+                $new_line_level  = $ends_line_level;
+                $ends_line_level = null;
+            }
+            if ($in_escape) {
+                $in_escape = false;
+            } elseif ($char === '"') {
+                $in_quotes = !$in_quotes;
+            } elseif (!$in_quotes) {
+                switch ($char) {
+                    case '}':
+                    case ']':
+                        $level--;
+                        $ends_line_level = null;
+                        $new_line_level  = $level;
+                        break;
+
+                    case '{':
+                    case '[':
+                        $level++;
+                    case ',':
+                        $ends_line_level = $level;
+                        break;
+
+                    case ':':
+                        $post = ' ';
+                        break;
+
+                    case ' ':
+                    case "\t":
+                    case "\n":
+                    case "\r":
+                        $char            = '';
+                        $ends_line_level = $new_line_level;
+                        $new_line_level  = null;
+                        break;
+                }
+            } elseif ($char === '\\') {
+                $in_escape = true;
+            }
+            if ($new_line_level !== null) {
+                $result .= "\n".str_repeat(str_repeat($spacer, $spacing), $new_line_level);
+            }
+            $result .= $char.$post;
+        }
+
+        $result = trim($result);
+
+        if (true === $newLineAtEof) {
+            $result .= "\n";
+        }
+
+        return $result;
+    }
+}
diff --git a/Parser/ParserInterface.php b/Parser/ParserInterface.php
new file mode 100644
index 0000000..f7f0ce4
--- /dev/null
+++ b/Parser/ParserInterface.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Incenteev\ParameterHandler\Parser;
+
+interface ParserInterface
+{
+    /**
+     * Parses a string to a PHP value.
+     *
+     * @param string $value A JSON string.
+     * @param int    $flags Bitmask of decode options.
+     *
+     * @return mixed A PHP value
+     *
+     * @throws ParseException If the string format is not valid
+     */
+    public function parse($value, $flags = 0);
+}
diff --git a/Parser/YamlParser.php b/Parser/YamlParser.php
new file mode 100644
index 0000000..0a3f25c
--- /dev/null
+++ b/Parser/YamlParser.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Incenteev\ParameterHandler\Parser;
+
+use Symfony\Component\Yaml\Parser;
+
+class YamlParser extends Parser implements ParserInterface
+{
+    // Intentionally left empty.
+}
diff --git a/Processor.php b/Processor/AbstractProcessor.php
similarity index 57%
rename from Processor.php
rename to Processor/AbstractProcessor.php
index 6dc208f..02fe246 100644
--- a/Processor.php
+++ b/Processor/AbstractProcessor.php
@@ -1,37 +1,60 @@
 <?php
 
-namespace Incenteev\ParameterHandler;
+namespace Incenteev\ParameterHandler\Processor;
 
 use Composer\IO\IOInterface;
+use Incenteev\ParameterHandler\Parser\ParseException;
+use Incenteev\ParameterHandler\Parser\ParserInterface;
 use Symfony\Component\Yaml\Inline;
-use Symfony\Component\Yaml\Parser;
-use Symfony\Component\Yaml\Yaml;
 
-class Processor
+abstract class AbstractProcessor
 {
-    private $io;
-
-    public function __construct(IOInterface $io)
+    /**
+     * IO Interface of composer used for displaying messages and requesting input from user.
+     *
+     * @var IOInterface
+     */
+    protected $io;
+
+    /**
+     * Parser.
+     *
+     * @var ParserInterface
+     */
+    protected $parser;
+
+    /**
+     * Constructor.
+     *
+     * @param IOInterface     $io     Composer IO
+     * @param ParserInterface $parser Instance of parser for type YAML or JSON
+     */
+    public function __construct(IOInterface $io, ParserInterface $parser)
     {
-        $this->io = $io;
+        $this->parser = $parser;
+        $this->io     = $io;
     }
 
+    /**
+     * Processes single operations for a passed parameter file configuration.
+     *
+     * @throws ParseException|\InvalidArgumentException|\RuntimeException
+     */
     public function processFile(array $config)
     {
         $config = $this->processConfig($config);
 
-        $realFile = $config['file'];
+        $realFile     = $config['file'];
         $parameterKey = $config['parameter-key'];
 
         $exists = is_file($realFile);
 
-        $yamlParser = new Parser();
-
         $action = $exists ? 'Updating' : 'Creating';
         $this->io->write(sprintf('<info>%s the "%s" file</info>', $action, $realFile));
 
         // Find the expected params
-        $expectedValues = $yamlParser->parse(file_get_contents($config['dist-file']));
+        $expectedValues = $this->parser->parse(file_get_contents($config['dist-file']));
+
         if (!isset($expectedValues[$parameterKey])) {
             throw new \InvalidArgumentException(sprintf('The top-level key %s is missing.', $parameterKey));
         }
@@ -39,12 +62,12 @@ public function processFile(array $config)
 
         // find the actual params
         $actualValues = array_merge(
-            // Preserve other top-level keys than `$parameterKey` in the file
+        // Preserve other top-level keys than `$parameterKey` in the file
             $expectedValues,
             array($parameterKey => array())
         );
         if ($exists) {
-            $existingValues = $yamlParser->parse(file_get_contents($realFile));
+            $existingValues = $this->parser->parse(file_get_contents($realFile));
             if ($existingValues === null) {
                 $existingValues = array();
             }
@@ -56,19 +79,24 @@ public function processFile(array $config)
 
         $actualValues[$parameterKey] = $this->processParams($config, $expectedParams, (array) $actualValues[$parameterKey]);
 
-        if (!is_dir($dir = dirname($realFile))) {
-            mkdir($dir, 0755, true);
+        if (!is_dir($dir = dirname($realFile)) && (!@mkdir($dir, 0755, true) && !is_dir($dir))) {
+            throw new \RuntimeException(
+                sprintf('Error while creating directory "%s". Check path and permissions.', $dir)
+            );
         }
 
-        file_put_contents($realFile, "# This file is auto-generated during the composer install\n" . Yaml::dump($actualValues, 99));
+        $this->writeFile($realFile, $actualValues);
     }
 
-    private function processConfig(array $config)
+    /**
+     * @param array $config
+     *
+     * @return array
+     *
+     * @throws \InvalidArgumentException
+     */
+    protected function processConfig(array $config)
     {
-        if (empty($config['file'])) {
-            throw new \InvalidArgumentException('The extra.incenteev-parameters.file setting is required to use this script handler.');
-        }
-
         if (empty($config['dist-file'])) {
             $config['dist-file'] = $config['file'].'.dist';
         }
@@ -84,10 +112,10 @@ private function processConfig(array $config)
         return $config;
     }
 
-    private function processParams(array $config, array $expectedParams, array $actualParams)
+    protected function processParams(array $config, array $expectedParams, array $actualParams)
     {
         // Grab values for parameters that were renamed
-        $renameMap = empty($config['rename-map']) ? array() : (array) $config['rename-map'];
+        $renameMap    = empty($config['rename-map']) ? array() : (array) $config['rename-map'];
         $actualParams = array_replace($actualParams, $this->processRenamedValues($renameMap, $actualParams));
 
         $keepOutdatedParams = false;
@@ -107,7 +135,16 @@ private function processParams(array $config, array $expectedParams, array $actu
         return $this->getParams($expectedParams, $actualParams);
     }
 
-    private function getEnvValues(array $envMap)
+    /**
+     * Parses environments variables by map and resolves correct types.
+     * As environment variables can only be strings, they are also parsed to allow specifying null, false,
+     * true or numbers easily.
+     *
+     * @param array $envMap Map used to map data from environment variable name to parameter name.
+     *
+     * @return array
+     */
+    protected function getEnvValues(array $envMap)
     {
         $params = array();
         foreach ($envMap as $param => $env) {
@@ -137,6 +174,18 @@ private function processRenamedValues(array $renameMap, array $actualParams)
         return $actualParams;
     }
 
+    /**
+     * Returns the current set of parameters.
+     * If IO mode non interactive it simply sets the expected values, otherwise it asks user for defining missing
+     * parameters.
+     *
+     * @param array $expectedParams Parameters required
+     * @param array $actualParams   Parameters defined already
+     *
+     * @return array Updated set of parameters
+     *
+     * @throws \RuntimeException
+     */
     private function getParams(array $expectedParams, array $actualParams)
     {
         // Simply use the expectedParams value as default for the missing params.
@@ -146,7 +195,7 @@ private function getParams(array $expectedParams, array $actualParams)
 
         $isStarted = false;
 
-        foreach ($expectedParams as $key => $message) {
+        foreach ($expectedParams as $key => $value) {
             if (array_key_exists($key, $actualParams)) {
                 continue;
             }
@@ -156,7 +205,8 @@ private function getParams(array $expectedParams, array $actualParams)
                 $this->io->write('<comment>Some parameters are missing. Please provide them.</comment>');
             }
 
-            $default = Inline::dump($message);
+            $default = Inline::dump($value);
+
             $value = $this->io->ask(sprintf('<question>%s</question> (<comment>%s</comment>): ', $key, $default), $default);
 
             $actualParams[$key] = Inline::parse($value);
@@ -164,4 +214,14 @@ private function getParams(array $expectedParams, array $actualParams)
 
         return $actualParams;
     }
+
+    /**
+     * Persists configuration.
+     *
+     * @param string $file          Filename to persist configuration to.
+     * @param array  $configuration Configuration to persist.
+     *
+     * @return bool TRUE after successful persisting the file, otherwise FALSE
+     */
+    abstract protected function writeFile($file, array $configuration);
 }
diff --git a/Processor/JsonProcessor.php b/Processor/JsonProcessor.php
new file mode 100644
index 0000000..e11b22c
--- /dev/null
+++ b/Processor/JsonProcessor.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Incenteev\ParameterHandler\Processor;
+
+class JsonProcessor extends AbstractProcessor
+{
+    /**
+     * Persists an array to a file in JSON format.
+     *
+     * {@inheritdoc}
+     */
+    protected function writeFile($filename, array $configuration)
+    {
+        return
+            false !== file_put_contents(
+                $filename, $this->parser->dump($configuration)
+            );
+    }
+}
diff --git a/Processor/YamlProcessor.php b/Processor/YamlProcessor.php
new file mode 100644
index 0000000..a57c3b0
--- /dev/null
+++ b/Processor/YamlProcessor.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Incenteev\ParameterHandler\Processor;
+
+use Symfony\Component\Yaml\Yaml;
+
+class YamlProcessor extends AbstractProcessor
+{
+    /**
+     * Persists an array to a file in YAML format.
+     *
+     * {@inheritdoc}
+     */
+    protected function writeFile($filename, array $configuration)
+    {
+        return
+            false !== file_put_contents(
+                $filename, "# This file is auto-generated during the composer install\n".Yaml::dump($configuration, 99)
+            );
+    }
+}
diff --git a/ScriptHandler.php b/ScriptHandler.php
index 165064a..767743a 100644
--- a/ScriptHandler.php
+++ b/ScriptHandler.php
@@ -3,9 +3,51 @@
 namespace Incenteev\ParameterHandler;
 
 use Composer\Script\Event;
+use Incenteev\ParameterHandler\Parser\JsonParser;
+use Incenteev\ParameterHandler\Parser\YamlParser;
+use Incenteev\ParameterHandler\Processor\JsonProcessor;
+use Incenteev\ParameterHandler\Processor\YamlProcessor;
 
 class ScriptHandler
 {
+    /**
+     * Configuration type YAML.
+     *
+     * @var string
+     */
+    const CONFIGURATION_FORMAT_YAML = 'yaml';
+
+    /**
+     * Extension of configuration type YAML.
+     *
+     * @var string
+     */
+    const FILE_EXTENSION_YAML = 'yml';
+
+    /**
+     * Configuration type JSON.
+     *
+     * @var string
+     */
+    const CONFIGURATION_FORMAT_JSON = 'json';
+
+    /**
+     * Extension of configuration type JSON.
+     *
+     * @var string
+     */
+    const FILE_EXTENSION_JSON = 'json';
+
+    /**
+     * Collection of handable types.
+     *
+     * @var array
+     */
+    protected static $handable = array(
+        self::CONFIGURATION_FORMAT_YAML,
+        self::CONFIGURATION_FORMAT_JSON,
+    );
+
     public static function buildParameters(Event $event)
     {
         $extras = $event->getComposer()->getPackage()->getExtra();
@@ -24,14 +66,60 @@ public static function buildParameters(Event $event)
             $configs = array($configs);
         }
 
-        $processor = new Processor($event->getIO());
-
         foreach ($configs as $config) {
             if (!is_array($config)) {
                 throw new \InvalidArgumentException('The extra.incenteev-parameters setting must be an array of configuration objects.');
             }
 
+            if (!array_key_exists('file', $config)) {
+                throw new \InvalidArgumentException('The extra.incenteev-parameters.file setting is required to use this script handler.');
+            }
+
+            $type = self::retrieveConfigurationTypeByFile($config['file']);
+
+            if (self::CONFIGURATION_FORMAT_YAML === $type) {
+                $processor = new YamlProcessor($event->getIO(), new YamlParser());
+            } elseif (self::FILE_EXTENSION_JSON === $type) {
+                $processor = new JsonProcessor($event->getIO(), new JsonParser());
+            } else {
+                throw new \OutOfBoundsException(
+                    sprintf(
+                        'Configuration format in file "%s" can not be handled. Currently supported: "%s"',
+                        $config['file'],
+                        var_export(self::$handable, true)
+                    )
+                );
+            }
+
             $processor->processFile($config);
         }
     }
+
+    /**
+     * Returns type of configuration by files extension.
+     * Files with extension ".yml" will be resolved to type YAML, extension ".json" will be resolved to type JSON
+     *
+     * @param string $file File to parse extension from
+     *
+     * @return string Type of configuration, either self::CONFIGURATION_FORMAT_YAML or self::CONFIGURATION_FORMAT_JSON
+     */
+    private static function retrieveConfigurationTypeByFile($file)
+    {
+        $info      = new \SplFileInfo($file);
+        $extension = strtolower($info->getExtension());
+
+        switch ($extension) {
+            case self::FILE_EXTENSION_YAML:
+                $type = self::CONFIGURATION_FORMAT_YAML;
+                break;
+            case self::FILE_EXTENSION_JSON:
+                $type = self::CONFIGURATION_FORMAT_JSON;
+                break;
+            default:
+                $type = null;
+                break;
+        }
+
+        return $type;
+    }
 }
diff --git a/Tests/JsonProcessorTest.php b/Tests/JsonProcessorTest.php
new file mode 100644
index 0000000..921f586
--- /dev/null
+++ b/Tests/JsonProcessorTest.php
@@ -0,0 +1,178 @@
+<?php
+
+namespace Incenteev\ParameterHandler\Tests;
+
+use Incenteev\ParameterHandler\Parser\JsonParser;
+use Incenteev\ParameterHandler\Processor\JsonProcessor;
+use Prophecy\PhpUnit\ProphecyTestCase;
+use Symfony\Component\Filesystem\Filesystem;
+use Symfony\Component\Yaml\Yaml;
+
+class JsonProcessorTest extends ProphecyTestCase
+{
+    /**
+     * @var \Composer\IO\IOInterface
+     */
+    private $io;
+
+    /**
+     * @var array
+     */
+    private $environmentBackup = array();
+
+    /**
+     * @var JsonProcessor
+     */
+    private $processor;
+
+    protected function setUp()
+    {
+        parent::setUp();
+
+        $this->io        = $this->prophesize('Composer\IO\IOInterface');
+        $this->processor = new JsonProcessor($this->io->reveal(), new JsonParser());
+    }
+
+    protected function tearDown()
+    {
+        parent::tearDown();
+
+        foreach ($this->environmentBackup as $var => $value) {
+            if (false === $value) {
+                putenv($var);
+            } else {
+                putenv($var.'='.$value);
+            }
+        }
+    }
+
+    /**
+     * @dataProvider provideInvalidConfiguration
+     */
+    public function testInvalidConfiguration(array $config, $exceptionMessage)
+    {
+        chdir(__DIR__);
+
+        $this->setExpectedException('InvalidArgumentException', $exceptionMessage);
+
+        $this->processor->processFile($config);
+    }
+
+    public function provideInvalidConfiguration()
+    {
+        return array(
+            'missing default dist file' => array(
+                array(
+                    'file' => 'fixtures/json/invalid/missing.json',
+                ),
+                'The dist file "fixtures/json/invalid/missing.json.dist" does not exist. Check your dist-file config or create it.',
+            ),
+            'missing custom dist file' => array(
+                array(
+                    'file'      => 'fixtures/json/invalid/missing.json',
+                    'dist-file' => 'fixtures/json/invalid/non-existent.dist.json',
+                ),
+                'The dist file "fixtures/json/invalid/non-existent.dist.json" does not exist. Check your dist-file config or create it.',
+            ),
+            'missing top level key in dist file' => array(
+                array(
+                    'file' => 'fixtures/json/invalid/missing_top_level.json',
+                ),
+                'The top-level key parameters is missing.',
+            ),
+            'invalid values in the existing file' => array(
+                array(
+                    'file' => 'fixtures/json/invalid/invalid_existing_values.json',
+                ),
+                'The existing "fixtures/json/invalid/invalid_existing_values.json" file does not contain an array',
+            ),
+        );
+    }
+
+    /**
+     * @dataProvider provideParameterHandlingTestCases
+     */
+    public function testParameterHandling($testCaseName)
+    {
+        $dataDir = __DIR__.'/fixtures/json/testcases/'.$testCaseName;
+
+        $testCase = array_replace_recursive(
+            array(
+                'title'  => 'unknown test',
+                'config' => array(
+                    'file' => 'parameters.json',
+                ),
+                'dist-file'   => 'parameters.json.dist',
+                'environment' => array(),
+                'interactive' => false,
+            ),
+            (array) Yaml::parse(file_get_contents($dataDir.'/setup.yml'))
+        );
+
+        $workingDir = sys_get_temp_dir().'/incenteev_parameter_handler';
+        $exists     = $this->initializeTestCase($testCase, $dataDir, $workingDir);
+
+        $message = sprintf('<info>%s the "%s" file</info>', $exists ? 'Updating' : 'Creating', $testCase['config']['file']);
+        $this->io->write($message)->shouldBeCalled();
+
+        $this->setInteractionExpectations($testCase);
+
+        $this->processor->processFile($testCase['config']);
+
+        $this->assertFileEquals($dataDir.'/expected.json', $workingDir.'/'.$testCase['config']['file'], $testCase['title']);
+    }
+
+    private function initializeTestCase(array $testCase, $dataDir, $workingDir)
+    {
+        $fs = new Filesystem();
+
+        if (is_dir($workingDir)) {
+            $fs->remove($workingDir);
+        }
+
+        $fs->copy($dataDir.'/dist.json', $workingDir.'/'.$testCase['dist-file']);
+
+        if ($exists = file_exists($dataDir.'/existing.json')) {
+            $fs->copy($dataDir.'/existing.json', $workingDir.'/'.$testCase['config']['file']);
+        }
+
+        foreach ($testCase['environment'] as $var => $value) {
+            $this->environmentBackup[$var] = getenv($var);
+            putenv($var.'='.$value);
+        }
+
+        chdir($workingDir);
+
+        return $exists;
+    }
+
+    private function setInteractionExpectations(array $testCase)
+    {
+        $this->io->isInteractive()->willReturn($testCase['interactive']);
+
+        if (!$testCase['interactive']) {
+            return;
+        }
+
+        if (!empty($testCase['requested_params'])) {
+            $this->io->write('<comment>Some parameters are missing. Please provide them.</comment>')->shouldBeCalledTimes(1);
+        }
+
+        foreach ($testCase['requested_params'] as $param => $settings) {
+            $this->io->ask(sprintf('<question>%s</question> (<comment>%s</comment>): ', $param, $settings['default']), $settings['default'])
+                ->willReturn($settings['input'])
+                ->shouldBeCalled();
+        }
+    }
+
+    public function provideParameterHandlingTestCases()
+    {
+        $tests = array();
+
+        foreach (glob(__DIR__.'/fixtures/json/testcases/*/') as $folder) {
+            $tests[] = array(basename($folder));
+        }
+
+        return $tests;
+    }
+}
diff --git a/Tests/ScriptHandlerTest.php b/Tests/ScriptHandlerTest.php
index b77e76a..44b8ec5 100644
--- a/Tests/ScriptHandlerTest.php
+++ b/Tests/ScriptHandlerTest.php
@@ -7,8 +7,19 @@
 
 class ScriptHandlerTest extends ProphecyTestCase
 {
+    /**
+     * @var \Composer\Script\Event
+     */
     private $event;
+
+    /**
+     * @var \Composer\IO\IOInterface
+     */
     private $io;
+
+    /**
+     * @var \Composer\Package\PackageInterface
+     */
     private $package;
 
     protected function setUp()
@@ -18,6 +29,7 @@ protected function setUp()
         $this->event = $this->prophesize('Composer\Script\Event');
         $this->io = $this->prophesize('Composer\IO\IOInterface');
         $this->package = $this->prophesize('Composer\Package\PackageInterface');
+        /* @var $composer \Composer\Composer */
         $composer = $this->prophesize('Composer\Composer');
 
         $composer->getPackage()->willReturn($this->package);
diff --git a/Tests/ProcessorTest.php b/Tests/YamlProcessorTest.php
similarity index 77%
rename from Tests/ProcessorTest.php
rename to Tests/YamlProcessorTest.php
index babf44a..226d31f 100644
--- a/Tests/ProcessorTest.php
+++ b/Tests/YamlProcessorTest.php
@@ -2,18 +2,26 @@
 
 namespace Incenteev\ParameterHandler\Tests;
 
-use Incenteev\ParameterHandler\Processor;
+use Incenteev\ParameterHandler\Parser\YamlParser;
+use Incenteev\ParameterHandler\Processor\YamlProcessor;
 use Prophecy\PhpUnit\ProphecyTestCase;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\Yaml\Yaml;
 
-class ProcessorTest extends ProphecyTestCase
+class YamlProcessorTest extends ProphecyTestCase
 {
+    /**
+     * @var \Composer\IO\IOInterface
+     */
     private $io;
+
+    /**
+     * @var array
+     */
     private $environmentBackup = array();
 
     /**
-     * @var Processor
+     * @var YamlProcessor
      */
     private $processor;
 
@@ -22,7 +30,7 @@ protected function setUp()
         parent::setUp();
 
         $this->io = $this->prophesize('Composer\IO\IOInterface');
-        $this->processor = new Processor($this->io->reveal());
+        $this->processor = new YamlProcessor($this->io->reveal(), new YamlParser());
     }
 
     protected function tearDown()
@@ -53,34 +61,30 @@ public function testInvalidConfiguration(array $config, $exceptionMessage)
     public function provideInvalidConfiguration()
     {
         return array(
-            'no file' => array(
-                array(),
-                'The extra.incenteev-parameters.file setting is required to use this script handler.',
-            ),
             'missing default dist file' => array(
                 array(
-                    'file' => 'fixtures/invalid/missing.yml',
+                    'file' => 'fixtures/yaml/invalid/missing.yml',
                 ),
-                'The dist file "fixtures/invalid/missing.yml.dist" does not exist. Check your dist-file config or create it.',
+                'The dist file "fixtures/yaml/invalid/missing.yml.dist" does not exist. Check your dist-file config or create it.',
             ),
             'missing custom dist file' => array(
                 array(
-                    'file' => 'fixtures/invalid/missing.yml',
-                    'dist-file' => 'fixtures/invalid/non-existent.dist.yml',
+                    'file' => 'fixtures/yaml/invalid/missing.yml',
+                    'dist-file' => 'fixtures/yaml/invalid/non-existent.dist.yml',
                 ),
-                'The dist file "fixtures/invalid/non-existent.dist.yml" does not exist. Check your dist-file config or create it.',
+                'The dist file "fixtures/yaml/invalid/non-existent.dist.yml" does not exist. Check your dist-file config or create it.',
             ),
             'missing top level key in dist file' => array(
                 array(
-                    'file' => 'fixtures/invalid/missing_top_level.yml',
+                    'file' => 'fixtures/yaml/invalid/missing_top_level.yml',
                 ),
                 'The top-level key parameters is missing.',
             ),
             'invalid values in the existing file' => array(
                 array(
-                    'file' => 'fixtures/invalid/invalid_existing_values.yml',
+                    'file' => 'fixtures/yaml/invalid/invalid_existing_values.yml',
                 ),
-                'The existing "fixtures/invalid/invalid_existing_values.yml" file does not contain an array',
+                'The existing "fixtures/yaml/invalid/invalid_existing_values.yml" file does not contain an array',
             ),
         );
     }
@@ -90,7 +94,7 @@ public function provideInvalidConfiguration()
      */
     public function testParameterHandling($testCaseName)
     {
-        $dataDir = __DIR__.'/fixtures/testcases/'.$testCaseName;
+        $dataDir = __DIR__.'/fixtures/yaml/testcases/'.$testCaseName;
 
         $testCase = array_replace_recursive(
             array(
@@ -135,7 +139,7 @@ private function initializeTestCase(array $testCase, $dataDir, $workingDir)
         foreach ($testCase['environment'] as $var => $value) {
             $this->environmentBackup[$var] = getenv($var);
             putenv($var.'='.$value);
-        };
+        }
 
         chdir($workingDir);
 
@@ -165,7 +169,7 @@ public function provideParameterHandlingTestCases()
     {
         $tests = array();
 
-        foreach (glob(__DIR__.'/fixtures/testcases/*/') as $folder) {
+        foreach (glob(__DIR__.'/fixtures/yaml/testcases/*/') as $folder) {
             $tests[] = array(basename($folder));
         }
 
diff --git a/Tests/fixtures/json/invalid/invalid_existing_values.json b/Tests/fixtures/json/invalid/invalid_existing_values.json
new file mode 100644
index 0000000..250c317
--- /dev/null
+++ b/Tests/fixtures/json/invalid/invalid_existing_values.json
@@ -0,0 +1 @@
+not valid json
\ No newline at end of file
diff --git a/Tests/fixtures/json/invalid/invalid_existing_values.json.dist b/Tests/fixtures/json/invalid/invalid_existing_values.json.dist
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/invalid/invalid_existing_values.json.dist
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/json/invalid/missing_top_level.json.dist b/Tests/fixtures/json/invalid/missing_top_level.json.dist
new file mode 100644
index 0000000..e63d37b
--- /dev/null
+++ b/Tests/fixtures/json/invalid/missing_top_level.json.dist
@@ -0,0 +1,3 @@
+{
+    "foo": "bar"
+}
diff --git a/Tests/fixtures/json/testcases/custom_dist_file/dist.json b/Tests/fixtures/json/testcases/custom_dist_file/dist.json
new file mode 100644
index 0000000..4d3059b
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_dist_file/dist.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false
+  }
+}
diff --git a/Tests/fixtures/json/testcases/custom_dist_file/existing.json b/Tests/fixtures/json/testcases/custom_dist_file/existing.json
new file mode 100644
index 0000000..869e880
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_dist_file/existing.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false
+  }
+}
diff --git a/Tests/fixtures/json/testcases/custom_dist_file/expected.json b/Tests/fixtures/json/testcases/custom_dist_file/expected.json
new file mode 100644
index 0000000..869e880
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_dist_file/expected.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false
+  }
+}
diff --git a/Tests/fixtures/json/testcases/custom_dist_file/setup.yml b/Tests/fixtures/json/testcases/custom_dist_file/setup.yml
new file mode 100644
index 0000000..d3d7fd9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_dist_file/setup.yml
@@ -0,0 +1,6 @@
+title: Existing values are kept
+
+config:
+    dist-file: parameters.dist.json
+
+dist-file: parameters.dist.json
diff --git a/Tests/fixtures/json/testcases/custom_key/dist.json b/Tests/fixtures/json/testcases/custom_key/dist.json
new file mode 100644
index 0000000..6dd3e6c
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_key/dist.json
@@ -0,0 +1,11 @@
+{
+  "config": {
+    "foo": "bar",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/json/testcases/custom_key/existing.json b/Tests/fixtures/json/testcases/custom_key/existing.json
new file mode 100644
index 0000000..52e0335
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_key/existing.json
@@ -0,0 +1,11 @@
+{
+  "config": {
+    "foo": "existing_foo",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/json/testcases/custom_key/expected.json b/Tests/fixtures/json/testcases/custom_key/expected.json
new file mode 100644
index 0000000..52e0335
--- /dev/null
+++ b/Tests/fixtures/json/testcases/custom_key/expected.json
@@ -0,0 +1,11 @@
+{
+  "config": {
+    "foo": "existing_foo",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/testcases/custom_key/setup.yml b/Tests/fixtures/json/testcases/custom_key/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_key/setup.yml
rename to Tests/fixtures/json/testcases/custom_key/setup.yml
diff --git a/Tests/fixtures/json/testcases/existent/dist.json b/Tests/fixtures/json/testcases/existent/dist.json
new file mode 100644
index 0000000..beb78e9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent/dist.json
@@ -0,0 +1,11 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/json/testcases/existent/existing.json b/Tests/fixtures/json/testcases/existent/existing.json
new file mode 100644
index 0000000..b4d4064
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent/existing.json
@@ -0,0 +1,11 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/json/testcases/existent/expected.json b/Tests/fixtures/json/testcases/existent/expected.json
new file mode 100644
index 0000000..b4d4064
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent/expected.json
@@ -0,0 +1,11 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/testcases/existent/setup.yml b/Tests/fixtures/json/testcases/existent/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent/setup.yml
rename to Tests/fixtures/json/testcases/existent/setup.yml
diff --git a/Tests/fixtures/json/testcases/existent_empty/dist.json b/Tests/fixtures/json/testcases/existent_empty/dist.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent_empty/dist.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/testcases/existent_empty/existing.yml b/Tests/fixtures/json/testcases/existent_empty/existing.json
similarity index 100%
rename from Tests/fixtures/testcases/existent_empty/existing.yml
rename to Tests/fixtures/json/testcases/existent_empty/existing.json
diff --git a/Tests/fixtures/json/testcases/existent_empty/expected.json b/Tests/fixtures/json/testcases/existent_empty/expected.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent_empty/expected.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/testcases/existent_empty/setup.yml b/Tests/fixtures/json/testcases/existent_empty/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_empty/setup.yml
rename to Tests/fixtures/json/testcases/existent_empty/setup.yml
diff --git a/Tests/fixtures/json/testcases/existent_without_key/dist.json b/Tests/fixtures/json/testcases/existent_without_key/dist.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent_without_key/dist.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/existent_without_key/existing.json b/Tests/fixtures/json/testcases/existent_without_key/existing.json
new file mode 100644
index 0000000..cbd009c
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent_without_key/existing.json
@@ -0,0 +1,3 @@
+{
+  "foobar": "baz"
+}
diff --git a/Tests/fixtures/json/testcases/existent_without_key/expected.json b/Tests/fixtures/json/testcases/existent_without_key/expected.json
new file mode 100644
index 0000000..daf3967
--- /dev/null
+++ b/Tests/fixtures/json/testcases/existent_without_key/expected.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "bar"
+  },
+  "foobar": "baz"
+}
diff --git a/Tests/fixtures/testcases/existent_without_key/setup.yml b/Tests/fixtures/json/testcases/existent_without_key/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_without_key/setup.yml
rename to Tests/fixtures/json/testcases/existent_without_key/setup.yml
diff --git a/Tests/fixtures/json/testcases/extra_keys/dist.json b/Tests/fixtures/json/testcases/extra_keys/dist.json
new file mode 100644
index 0000000..11d2fd9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/extra_keys/dist.json
@@ -0,0 +1,7 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false
+  },
+  "extra_key": "a new extra key"
+}
diff --git a/Tests/fixtures/json/testcases/extra_keys/existing.json b/Tests/fixtures/json/testcases/extra_keys/existing.json
new file mode 100644
index 0000000..a5e6df1
--- /dev/null
+++ b/Tests/fixtures/json/testcases/extra_keys/existing.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo"
+  },
+  "another_key": "foo"
+}
diff --git a/Tests/fixtures/json/testcases/extra_keys/expected.json b/Tests/fixtures/json/testcases/extra_keys/expected.json
new file mode 100644
index 0000000..d6ea26f
--- /dev/null
+++ b/Tests/fixtures/json/testcases/extra_keys/expected.json
@@ -0,0 +1,8 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false
+  },
+  "extra_key": "a new extra key",
+  "another_key": "foo"
+}
diff --git a/Tests/fixtures/testcases/extra_keys/setup.yml b/Tests/fixtures/json/testcases/extra_keys/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/extra_keys/setup.yml
rename to Tests/fixtures/json/testcases/extra_keys/setup.yml
diff --git a/Tests/fixtures/json/testcases/interaction_existent/dist.json b/Tests/fixtures/json/testcases/interaction_existent/dist.json
new file mode 100644
index 0000000..839fab3
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_existent/dist.json
@@ -0,0 +1,7 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false,
+    "another": null
+  }
+}
diff --git a/Tests/fixtures/json/testcases/interaction_existent/existing.json b/Tests/fixtures/json/testcases/interaction_existent/existing.json
new file mode 100644
index 0000000..57437bc
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_existent/existing.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "existing_foo"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/interaction_existent/expected.json b/Tests/fixtures/json/testcases/interaction_existent/expected.json
new file mode 100644
index 0000000..fd746b9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_existent/expected.json
@@ -0,0 +1,7 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false,
+    "another": "null"
+  }
+}
diff --git a/Tests/fixtures/testcases/interaction_existent/setup.yml b/Tests/fixtures/json/testcases/interaction_existent/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_existent/setup.yml
rename to Tests/fixtures/json/testcases/interaction_existent/setup.yml
diff --git a/Tests/fixtures/json/testcases/interaction_non_existent/dist.json b/Tests/fixtures/json/testcases/interaction_non_existent/dist.json
new file mode 100644
index 0000000..3412193
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_non_existent/dist.json
@@ -0,0 +1,7 @@
+{
+  "parameters": {
+    "boolean": false,
+    "another": "test",
+    "nested": "nested"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/interaction_non_existent/expected.json b/Tests/fixtures/json/testcases/interaction_non_existent/expected.json
new file mode 100644
index 0000000..6c251bb
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_non_existent/expected.json
@@ -0,0 +1,14 @@
+{
+  "parameters": {
+    "boolean": true,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": [
+        "foo",
+        "test",
+        null
+      ]
+    }
+  }
+}
diff --git a/Tests/fixtures/testcases/interaction_non_existent/setup.yml b/Tests/fixtures/json/testcases/interaction_non_existent/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_non_existent/setup.yml
rename to Tests/fixtures/json/testcases/interaction_non_existent/setup.yml
diff --git a/Tests/fixtures/json/testcases/interaction_with_environment/dist.json b/Tests/fixtures/json/testcases/interaction_with_environment/dist.json
new file mode 100644
index 0000000..3412193
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_with_environment/dist.json
@@ -0,0 +1,7 @@
+{
+  "parameters": {
+    "boolean": false,
+    "another": "test",
+    "nested": "nested"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/interaction_with_environment/expected.json b/Tests/fixtures/json/testcases/interaction_with_environment/expected.json
new file mode 100644
index 0000000..904b4ff
--- /dev/null
+++ b/Tests/fixtures/json/testcases/interaction_with_environment/expected.json
@@ -0,0 +1,14 @@
+{
+  "parameters": {
+    "boolean": true,
+    "nested": {
+      "foo": "env_foo",
+      "bar": [
+        "env",
+        "test",
+        null
+      ]
+    },
+    "another": null
+  }
+}
diff --git a/Tests/fixtures/testcases/interaction_with_environment/setup.yml b/Tests/fixtures/json/testcases/interaction_with_environment/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_with_environment/setup.yml
rename to Tests/fixtures/json/testcases/interaction_with_environment/setup.yml
diff --git a/Tests/fixtures/json/testcases/keep_outdated/dist.json b/Tests/fixtures/json/testcases/keep_outdated/dist.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/keep_outdated/dist.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/keep_outdated/existing.json b/Tests/fixtures/json/testcases/keep_outdated/existing.json
new file mode 100644
index 0000000..ee8f822
--- /dev/null
+++ b/Tests/fixtures/json/testcases/keep_outdated/existing.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "outdated": "outdated_param"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/keep_outdated/expected.json b/Tests/fixtures/json/testcases/keep_outdated/expected.json
new file mode 100644
index 0000000..ee8f822
--- /dev/null
+++ b/Tests/fixtures/json/testcases/keep_outdated/expected.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "outdated": "outdated_param"
+  }
+}
diff --git a/Tests/fixtures/testcases/keep_outdated/setup.yml b/Tests/fixtures/json/testcases/keep_outdated/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/keep_outdated/setup.yml
rename to Tests/fixtures/json/testcases/keep_outdated/setup.yml
diff --git a/Tests/fixtures/json/testcases/non_existent/dist.json b/Tests/fixtures/json/testcases/non_existent/dist.json
new file mode 100644
index 0000000..beb78e9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/non_existent/dist.json
@@ -0,0 +1,11 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/json/testcases/non_existent/expected.json b/Tests/fixtures/json/testcases/non_existent/expected.json
new file mode 100644
index 0000000..beb78e9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/non_existent/expected.json
@@ -0,0 +1,11 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/testcases/non_existent/setup.yml b/Tests/fixtures/json/testcases/non_existent/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/non_existent/setup.yml
rename to Tests/fixtures/json/testcases/non_existent/setup.yml
diff --git a/Tests/fixtures/json/testcases/non_existent_with_environment/dist.json b/Tests/fixtures/json/testcases/non_existent_with_environment/dist.json
new file mode 100644
index 0000000..beb78e9
--- /dev/null
+++ b/Tests/fixtures/json/testcases/non_existent_with_environment/dist.json
@@ -0,0 +1,11 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false,
+    "another": null,
+    "nested": {
+      "foo": "bar",
+      "bar": "baz"
+    }
+  }
+}
diff --git a/Tests/fixtures/json/testcases/non_existent_with_environment/expected.json b/Tests/fixtures/json/testcases/non_existent_with_environment/expected.json
new file mode 100644
index 0000000..bc36e58
--- /dev/null
+++ b/Tests/fixtures/json/testcases/non_existent_with_environment/expected.json
@@ -0,0 +1,15 @@
+{
+  "parameters": {
+    "foo": "foobar",
+    "boolean": true,
+    "another": null,
+    "nested": {
+      "foo": "env_foo",
+      "bar": [
+        "env",
+        "test",
+        null
+      ]
+    }
+  }
+}
diff --git a/Tests/fixtures/testcases/non_existent_with_environment/setup.yml b/Tests/fixtures/json/testcases/non_existent_with_environment/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/non_existent_with_environment/setup.yml
rename to Tests/fixtures/json/testcases/non_existent_with_environment/setup.yml
diff --git a/Tests/fixtures/json/testcases/remove_outdated/dist.json b/Tests/fixtures/json/testcases/remove_outdated/dist.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/remove_outdated/dist.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/remove_outdated/existing.json b/Tests/fixtures/json/testcases/remove_outdated/existing.json
new file mode 100644
index 0000000..ee8f822
--- /dev/null
+++ b/Tests/fixtures/json/testcases/remove_outdated/existing.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "outdated": "outdated_param"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/remove_outdated/expected.json b/Tests/fixtures/json/testcases/remove_outdated/expected.json
new file mode 100644
index 0000000..57437bc
--- /dev/null
+++ b/Tests/fixtures/json/testcases/remove_outdated/expected.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "existing_foo"
+  }
+}
diff --git a/Tests/fixtures/testcases/remove_outdated/setup.yml b/Tests/fixtures/json/testcases/remove_outdated/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/remove_outdated/setup.yml
rename to Tests/fixtures/json/testcases/remove_outdated/setup.yml
diff --git a/Tests/fixtures/json/testcases/renamed/dist.json b/Tests/fixtures/json/testcases/renamed/dist.json
new file mode 100644
index 0000000..2547e1a
--- /dev/null
+++ b/Tests/fixtures/json/testcases/renamed/dist.json
@@ -0,0 +1,9 @@
+{
+  "parameters": {
+    "new": "bar",
+    "new2": "new2",
+    "new3": "test",
+    "new4": "test4",
+    "new5": "test5"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/renamed/existing.json b/Tests/fixtures/json/testcases/renamed/existing.json
new file mode 100644
index 0000000..763a2bc
--- /dev/null
+++ b/Tests/fixtures/json/testcases/renamed/existing.json
@@ -0,0 +1,8 @@
+{
+  "parameters": {
+    "old": "old_value",
+    "new2": "foo",
+    "old2": "bar",
+    "old4": "old4"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/renamed/expected.json b/Tests/fixtures/json/testcases/renamed/expected.json
new file mode 100644
index 0000000..5ec77ae
--- /dev/null
+++ b/Tests/fixtures/json/testcases/renamed/expected.json
@@ -0,0 +1,9 @@
+{
+  "parameters": {
+    "new": "old_value",
+    "new2": "foo",
+    "new3": "test",
+    "new4": "old4",
+    "new5": "old4"
+  }
+}
diff --git a/Tests/fixtures/testcases/renamed/setup.yml b/Tests/fixtures/json/testcases/renamed/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed/setup.yml
rename to Tests/fixtures/json/testcases/renamed/setup.yml
diff --git a/Tests/fixtures/json/testcases/renamed_and_environment/dist.json b/Tests/fixtures/json/testcases/renamed_and_environment/dist.json
new file mode 100644
index 0000000..0ce2ab4
--- /dev/null
+++ b/Tests/fixtures/json/testcases/renamed_and_environment/dist.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "new": "bar",
+    "new2": "new2"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/renamed_and_environment/existing.json b/Tests/fixtures/json/testcases/renamed_and_environment/existing.json
new file mode 100644
index 0000000..cad0abb
--- /dev/null
+++ b/Tests/fixtures/json/testcases/renamed_and_environment/existing.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "old": "old_value",
+    "old2": "old_value2"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/renamed_and_environment/expected.json b/Tests/fixtures/json/testcases/renamed_and_environment/expected.json
new file mode 100644
index 0000000..cb24ebe
--- /dev/null
+++ b/Tests/fixtures/json/testcases/renamed_and_environment/expected.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "new": "new_env_value",
+    "new2": "old_value2"
+  }
+}
diff --git a/Tests/fixtures/testcases/renamed_and_environment/setup.yml b/Tests/fixtures/json/testcases/renamed_and_environment/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed_and_environment/setup.yml
rename to Tests/fixtures/json/testcases/renamed_and_environment/setup.yml
diff --git a/Tests/fixtures/json/testcases/subfolder/dist.json b/Tests/fixtures/json/testcases/subfolder/dist.json
new file mode 100644
index 0000000..4d3059b
--- /dev/null
+++ b/Tests/fixtures/json/testcases/subfolder/dist.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "bar",
+    "boolean": false
+  }
+}
diff --git a/Tests/fixtures/json/testcases/subfolder/existing.json b/Tests/fixtures/json/testcases/subfolder/existing.json
new file mode 100644
index 0000000..869e880
--- /dev/null
+++ b/Tests/fixtures/json/testcases/subfolder/existing.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false
+  }
+}
diff --git a/Tests/fixtures/json/testcases/subfolder/expected.json b/Tests/fixtures/json/testcases/subfolder/expected.json
new file mode 100644
index 0000000..869e880
--- /dev/null
+++ b/Tests/fixtures/json/testcases/subfolder/expected.json
@@ -0,0 +1,6 @@
+{
+  "parameters": {
+    "foo": "existing_foo",
+    "boolean": false
+  }
+}
diff --git a/Tests/fixtures/testcases/subfolder/setup.yml b/Tests/fixtures/json/testcases/subfolder/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder/setup.yml
rename to Tests/fixtures/json/testcases/subfolder/setup.yml
diff --git a/Tests/fixtures/json/testcases/subfolder_created/dist.json b/Tests/fixtures/json/testcases/subfolder_created/dist.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/subfolder_created/dist.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/json/testcases/subfolder_created/expected.json b/Tests/fixtures/json/testcases/subfolder_created/expected.json
new file mode 100644
index 0000000..e797330
--- /dev/null
+++ b/Tests/fixtures/json/testcases/subfolder_created/expected.json
@@ -0,0 +1,5 @@
+{
+  "parameters": {
+    "foo": "bar"
+  }
+}
diff --git a/Tests/fixtures/testcases/subfolder_created/setup.yml b/Tests/fixtures/json/testcases/subfolder_created/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder_created/setup.yml
rename to Tests/fixtures/json/testcases/subfolder_created/setup.yml
diff --git a/Tests/fixtures/invalid/invalid_existing_values.yml b/Tests/fixtures/yaml/invalid/invalid_existing_values.yml
similarity index 100%
rename from Tests/fixtures/invalid/invalid_existing_values.yml
rename to Tests/fixtures/yaml/invalid/invalid_existing_values.yml
diff --git a/Tests/fixtures/invalid/invalid_existing_values.yml.dist b/Tests/fixtures/yaml/invalid/invalid_existing_values.yml.dist
similarity index 100%
rename from Tests/fixtures/invalid/invalid_existing_values.yml.dist
rename to Tests/fixtures/yaml/invalid/invalid_existing_values.yml.dist
diff --git a/Tests/fixtures/invalid/missing_top_level.yml.dist b/Tests/fixtures/yaml/invalid/missing_top_level.yml.dist
similarity index 100%
rename from Tests/fixtures/invalid/missing_top_level.yml.dist
rename to Tests/fixtures/yaml/invalid/missing_top_level.yml.dist
diff --git a/Tests/fixtures/testcases/custom_dist_file/dist.yml b/Tests/fixtures/yaml/testcases/custom_dist_file/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_dist_file/dist.yml
rename to Tests/fixtures/yaml/testcases/custom_dist_file/dist.yml
diff --git a/Tests/fixtures/testcases/custom_dist_file/existing.yml b/Tests/fixtures/yaml/testcases/custom_dist_file/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_dist_file/existing.yml
rename to Tests/fixtures/yaml/testcases/custom_dist_file/existing.yml
diff --git a/Tests/fixtures/testcases/custom_dist_file/expected.yml b/Tests/fixtures/yaml/testcases/custom_dist_file/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_dist_file/expected.yml
rename to Tests/fixtures/yaml/testcases/custom_dist_file/expected.yml
diff --git a/Tests/fixtures/testcases/custom_dist_file/setup.yml b/Tests/fixtures/yaml/testcases/custom_dist_file/setup.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_dist_file/setup.yml
rename to Tests/fixtures/yaml/testcases/custom_dist_file/setup.yml
diff --git a/Tests/fixtures/testcases/custom_key/dist.yml b/Tests/fixtures/yaml/testcases/custom_key/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_key/dist.yml
rename to Tests/fixtures/yaml/testcases/custom_key/dist.yml
diff --git a/Tests/fixtures/testcases/custom_key/existing.yml b/Tests/fixtures/yaml/testcases/custom_key/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_key/existing.yml
rename to Tests/fixtures/yaml/testcases/custom_key/existing.yml
diff --git a/Tests/fixtures/testcases/custom_key/expected.yml b/Tests/fixtures/yaml/testcases/custom_key/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/custom_key/expected.yml
rename to Tests/fixtures/yaml/testcases/custom_key/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/custom_key/setup.yml b/Tests/fixtures/yaml/testcases/custom_key/setup.yml
new file mode 100644
index 0000000..6611ac7
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/custom_key/setup.yml
@@ -0,0 +1,5 @@
+title: Using a custom parameter key
+
+config:
+    parameter-key: config
+
diff --git a/Tests/fixtures/testcases/existent/dist.yml b/Tests/fixtures/yaml/testcases/existent/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent/dist.yml
rename to Tests/fixtures/yaml/testcases/existent/dist.yml
diff --git a/Tests/fixtures/testcases/existent/existing.yml b/Tests/fixtures/yaml/testcases/existent/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent/existing.yml
rename to Tests/fixtures/yaml/testcases/existent/existing.yml
diff --git a/Tests/fixtures/testcases/existent/expected.yml b/Tests/fixtures/yaml/testcases/existent/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent/expected.yml
rename to Tests/fixtures/yaml/testcases/existent/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/existent/setup.yml b/Tests/fixtures/yaml/testcases/existent/setup.yml
new file mode 100644
index 0000000..b72f1b5
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/existent/setup.yml
@@ -0,0 +1 @@
+title: Existing values are kept
diff --git a/Tests/fixtures/testcases/existent_empty/dist.yml b/Tests/fixtures/yaml/testcases/existent_empty/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_empty/dist.yml
rename to Tests/fixtures/yaml/testcases/existent_empty/dist.yml
diff --git a/Tests/fixtures/yaml/testcases/existent_empty/existing.yml b/Tests/fixtures/yaml/testcases/existent_empty/existing.yml
new file mode 100644
index 0000000..e69de29
diff --git a/Tests/fixtures/testcases/existent_empty/expected.yml b/Tests/fixtures/yaml/testcases/existent_empty/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_empty/expected.yml
rename to Tests/fixtures/yaml/testcases/existent_empty/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/existent_empty/setup.yml b/Tests/fixtures/yaml/testcases/existent_empty/setup.yml
new file mode 100644
index 0000000..dedcd0f
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/existent_empty/setup.yml
@@ -0,0 +1 @@
+title: Existing empty files are valid (Capifony compatibility)
diff --git a/Tests/fixtures/testcases/existent_without_key/dist.yml b/Tests/fixtures/yaml/testcases/existent_without_key/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_without_key/dist.yml
rename to Tests/fixtures/yaml/testcases/existent_without_key/dist.yml
diff --git a/Tests/fixtures/testcases/existent_without_key/existing.yml b/Tests/fixtures/yaml/testcases/existent_without_key/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_without_key/existing.yml
rename to Tests/fixtures/yaml/testcases/existent_without_key/existing.yml
diff --git a/Tests/fixtures/testcases/existent_without_key/expected.yml b/Tests/fixtures/yaml/testcases/existent_without_key/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/existent_without_key/expected.yml
rename to Tests/fixtures/yaml/testcases/existent_without_key/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/existent_without_key/setup.yml b/Tests/fixtures/yaml/testcases/existent_without_key/setup.yml
new file mode 100644
index 0000000..3797a0b
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/existent_without_key/setup.yml
@@ -0,0 +1 @@
+title: Existing files without the parameters key are valid
diff --git a/Tests/fixtures/testcases/extra_keys/dist.yml b/Tests/fixtures/yaml/testcases/extra_keys/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/extra_keys/dist.yml
rename to Tests/fixtures/yaml/testcases/extra_keys/dist.yml
diff --git a/Tests/fixtures/testcases/extra_keys/existing.yml b/Tests/fixtures/yaml/testcases/extra_keys/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/extra_keys/existing.yml
rename to Tests/fixtures/yaml/testcases/extra_keys/existing.yml
diff --git a/Tests/fixtures/testcases/extra_keys/expected.yml b/Tests/fixtures/yaml/testcases/extra_keys/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/extra_keys/expected.yml
rename to Tests/fixtures/yaml/testcases/extra_keys/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/extra_keys/setup.yml b/Tests/fixtures/yaml/testcases/extra_keys/setup.yml
new file mode 100644
index 0000000..50666fd
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/extra_keys/setup.yml
@@ -0,0 +1 @@
+title: Extra top level keys are preserved
diff --git a/Tests/fixtures/testcases/interaction_existent/dist.yml b/Tests/fixtures/yaml/testcases/interaction_existent/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_existent/dist.yml
rename to Tests/fixtures/yaml/testcases/interaction_existent/dist.yml
diff --git a/Tests/fixtures/testcases/interaction_existent/existing.yml b/Tests/fixtures/yaml/testcases/interaction_existent/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_existent/existing.yml
rename to Tests/fixtures/yaml/testcases/interaction_existent/existing.yml
diff --git a/Tests/fixtures/testcases/interaction_existent/expected.yml b/Tests/fixtures/yaml/testcases/interaction_existent/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_existent/expected.yml
rename to Tests/fixtures/yaml/testcases/interaction_existent/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/interaction_existent/setup.yml b/Tests/fixtures/yaml/testcases/interaction_existent/setup.yml
new file mode 100644
index 0000000..79664cb
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/interaction_existent/setup.yml
@@ -0,0 +1,11 @@
+title: Existing values are not asked interactively again
+
+interactive: true
+
+requested_params:
+    boolean:
+        default: 'false'
+        input: 'false'
+    another:
+        default: 'null'
+        input: '"null"'
diff --git a/Tests/fixtures/testcases/interaction_non_existent/dist.yml b/Tests/fixtures/yaml/testcases/interaction_non_existent/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_non_existent/dist.yml
rename to Tests/fixtures/yaml/testcases/interaction_non_existent/dist.yml
diff --git a/Tests/fixtures/testcases/interaction_non_existent/expected.yml b/Tests/fixtures/yaml/testcases/interaction_non_existent/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_non_existent/expected.yml
rename to Tests/fixtures/yaml/testcases/interaction_non_existent/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/interaction_non_existent/setup.yml b/Tests/fixtures/yaml/testcases/interaction_non_existent/setup.yml
new file mode 100644
index 0000000..40effce
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/interaction_non_existent/setup.yml
@@ -0,0 +1,14 @@
+title: Missing keys are asked interactively
+
+interactive: true
+
+requested_params:
+    boolean:
+        default: 'false'
+        input: 'true'
+    nested:
+        default: nested
+        input: '{foo: bar, bar: [foo, test, null]}'
+    another:
+        default: test
+        input: 'null'
diff --git a/Tests/fixtures/testcases/interaction_with_environment/dist.yml b/Tests/fixtures/yaml/testcases/interaction_with_environment/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_with_environment/dist.yml
rename to Tests/fixtures/yaml/testcases/interaction_with_environment/dist.yml
diff --git a/Tests/fixtures/testcases/interaction_with_environment/expected.yml b/Tests/fixtures/yaml/testcases/interaction_with_environment/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/interaction_with_environment/expected.yml
rename to Tests/fixtures/yaml/testcases/interaction_with_environment/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/interaction_with_environment/setup.yml b/Tests/fixtures/yaml/testcases/interaction_with_environment/setup.yml
new file mode 100644
index 0000000..80e2585
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/interaction_with_environment/setup.yml
@@ -0,0 +1,17 @@
+title: Values provided by the environment are not asked interactively
+
+config:
+    env-map:
+        boolean: IC_TEST_BOOL
+        nested: IC_TEST_NESTED
+
+environment:
+    IC_TEST_BOOL: 'true'
+    IC_TEST_NESTED: '{foo: env_foo, bar: [env, test, null]}'
+
+interactive: true
+
+requested_params:
+    another:
+        default: test
+        input: 'null'
diff --git a/Tests/fixtures/testcases/keep_outdated/dist.yml b/Tests/fixtures/yaml/testcases/keep_outdated/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/keep_outdated/dist.yml
rename to Tests/fixtures/yaml/testcases/keep_outdated/dist.yml
diff --git a/Tests/fixtures/testcases/keep_outdated/existing.yml b/Tests/fixtures/yaml/testcases/keep_outdated/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/keep_outdated/existing.yml
rename to Tests/fixtures/yaml/testcases/keep_outdated/existing.yml
diff --git a/Tests/fixtures/testcases/keep_outdated/expected.yml b/Tests/fixtures/yaml/testcases/keep_outdated/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/keep_outdated/expected.yml
rename to Tests/fixtures/yaml/testcases/keep_outdated/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/keep_outdated/setup.yml b/Tests/fixtures/yaml/testcases/keep_outdated/setup.yml
new file mode 100644
index 0000000..d3f2eec
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/keep_outdated/setup.yml
@@ -0,0 +1,4 @@
+title: Outdated keys can be kept in the parameters file
+
+config:
+    keep-outdated: true
diff --git a/Tests/fixtures/testcases/non_existent/dist.yml b/Tests/fixtures/yaml/testcases/non_existent/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/non_existent/dist.yml
rename to Tests/fixtures/yaml/testcases/non_existent/dist.yml
diff --git a/Tests/fixtures/testcases/non_existent/expected.yml b/Tests/fixtures/yaml/testcases/non_existent/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/non_existent/expected.yml
rename to Tests/fixtures/yaml/testcases/non_existent/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/non_existent/setup.yml b/Tests/fixtures/yaml/testcases/non_existent/setup.yml
new file mode 100644
index 0000000..9c33d2d
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/non_existent/setup.yml
@@ -0,0 +1 @@
+title: Non existent files are created
diff --git a/Tests/fixtures/testcases/non_existent_with_environment/dist.yml b/Tests/fixtures/yaml/testcases/non_existent_with_environment/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/non_existent_with_environment/dist.yml
rename to Tests/fixtures/yaml/testcases/non_existent_with_environment/dist.yml
diff --git a/Tests/fixtures/testcases/non_existent_with_environment/expected.yml b/Tests/fixtures/yaml/testcases/non_existent_with_environment/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/non_existent_with_environment/expected.yml
rename to Tests/fixtures/yaml/testcases/non_existent_with_environment/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/non_existent_with_environment/setup.yml b/Tests/fixtures/yaml/testcases/non_existent_with_environment/setup.yml
new file mode 100644
index 0000000..684e4de
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/non_existent_with_environment/setup.yml
@@ -0,0 +1,13 @@
+title: Environment variables are used over dist file defaults
+
+config:
+    env-map:
+        boolean: IC_TEST_BOOL
+        foo: IC_TEST_FOO
+        nested: IC_TEST_NESTED
+        another: IC_TEST_NOT_SET
+
+environment:
+    IC_TEST_BOOL: 'true'
+    IC_TEST_FOO: 'foobar'
+    IC_TEST_NESTED: '{foo: env_foo, bar: [env, test, null]}'
diff --git a/Tests/fixtures/testcases/remove_outdated/dist.yml b/Tests/fixtures/yaml/testcases/remove_outdated/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/remove_outdated/dist.yml
rename to Tests/fixtures/yaml/testcases/remove_outdated/dist.yml
diff --git a/Tests/fixtures/testcases/remove_outdated/existing.yml b/Tests/fixtures/yaml/testcases/remove_outdated/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/remove_outdated/existing.yml
rename to Tests/fixtures/yaml/testcases/remove_outdated/existing.yml
diff --git a/Tests/fixtures/testcases/remove_outdated/expected.yml b/Tests/fixtures/yaml/testcases/remove_outdated/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/remove_outdated/expected.yml
rename to Tests/fixtures/yaml/testcases/remove_outdated/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/remove_outdated/setup.yml b/Tests/fixtures/yaml/testcases/remove_outdated/setup.yml
new file mode 100644
index 0000000..183e5cd
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/remove_outdated/setup.yml
@@ -0,0 +1 @@
+title: Outdated keys are removed from the parameters file
diff --git a/Tests/fixtures/testcases/renamed/dist.yml b/Tests/fixtures/yaml/testcases/renamed/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed/dist.yml
rename to Tests/fixtures/yaml/testcases/renamed/dist.yml
diff --git a/Tests/fixtures/testcases/renamed/existing.yml b/Tests/fixtures/yaml/testcases/renamed/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed/existing.yml
rename to Tests/fixtures/yaml/testcases/renamed/existing.yml
diff --git a/Tests/fixtures/testcases/renamed/expected.yml b/Tests/fixtures/yaml/testcases/renamed/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed/expected.yml
rename to Tests/fixtures/yaml/testcases/renamed/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/renamed/setup.yml b/Tests/fixtures/yaml/testcases/renamed/setup.yml
new file mode 100644
index 0000000..153ed8c
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/renamed/setup.yml
@@ -0,0 +1,9 @@
+title: Key can be renamed and the value is reused
+
+config:
+    rename-map:
+        new: old
+        new2: old2
+        new3: old3
+        new4: old4
+        new5: new4 # Cascade renaming
diff --git a/Tests/fixtures/testcases/renamed_and_environment/dist.yml b/Tests/fixtures/yaml/testcases/renamed_and_environment/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed_and_environment/dist.yml
rename to Tests/fixtures/yaml/testcases/renamed_and_environment/dist.yml
diff --git a/Tests/fixtures/testcases/renamed_and_environment/existing.yml b/Tests/fixtures/yaml/testcases/renamed_and_environment/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed_and_environment/existing.yml
rename to Tests/fixtures/yaml/testcases/renamed_and_environment/existing.yml
diff --git a/Tests/fixtures/testcases/renamed_and_environment/expected.yml b/Tests/fixtures/yaml/testcases/renamed_and_environment/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/renamed_and_environment/expected.yml
rename to Tests/fixtures/yaml/testcases/renamed_and_environment/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/renamed_and_environment/setup.yml b/Tests/fixtures/yaml/testcases/renamed_and_environment/setup.yml
new file mode 100644
index 0000000..7c3853f
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/renamed_and_environment/setup.yml
@@ -0,0 +1,11 @@
+title: Environment variables win over renamed keys
+
+config:
+    rename-map:
+        new: old
+        new2: old2
+    env-map:
+        new: IC_TEST_NEW
+
+environment:
+    IC_TEST_NEW: 'new_env_value'
diff --git a/Tests/fixtures/testcases/subfolder/dist.yml b/Tests/fixtures/yaml/testcases/subfolder/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder/dist.yml
rename to Tests/fixtures/yaml/testcases/subfolder/dist.yml
diff --git a/Tests/fixtures/testcases/subfolder/existing.yml b/Tests/fixtures/yaml/testcases/subfolder/existing.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder/existing.yml
rename to Tests/fixtures/yaml/testcases/subfolder/existing.yml
diff --git a/Tests/fixtures/testcases/subfolder/expected.yml b/Tests/fixtures/yaml/testcases/subfolder/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder/expected.yml
rename to Tests/fixtures/yaml/testcases/subfolder/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/subfolder/setup.yml b/Tests/fixtures/yaml/testcases/subfolder/setup.yml
new file mode 100644
index 0000000..21a4b00
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/subfolder/setup.yml
@@ -0,0 +1,6 @@
+title: Files can be located in subfolders
+
+config:
+    file: 'app/parameters.yml'
+
+dist-file: 'app/parameters.yml.dist'
diff --git a/Tests/fixtures/testcases/subfolder_created/dist.yml b/Tests/fixtures/yaml/testcases/subfolder_created/dist.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder_created/dist.yml
rename to Tests/fixtures/yaml/testcases/subfolder_created/dist.yml
diff --git a/Tests/fixtures/testcases/subfolder_created/expected.yml b/Tests/fixtures/yaml/testcases/subfolder_created/expected.yml
similarity index 100%
rename from Tests/fixtures/testcases/subfolder_created/expected.yml
rename to Tests/fixtures/yaml/testcases/subfolder_created/expected.yml
diff --git a/Tests/fixtures/yaml/testcases/subfolder_created/setup.yml b/Tests/fixtures/yaml/testcases/subfolder_created/setup.yml
new file mode 100644
index 0000000..c30049a
--- /dev/null
+++ b/Tests/fixtures/yaml/testcases/subfolder_created/setup.yml
@@ -0,0 +1,7 @@
+title: Files can be located in different folders than the dist and the folder is created
+
+config:
+    file: 'app/parameters.yml'
+    dist-file: 'dist/parameters.yml'
+
+dist-file: 'dist/parameters.yml'
diff --git a/composer.json b/composer.json
index 784ccfd..7b2251c 100644
--- a/composer.json
+++ b/composer.json
@@ -12,12 +12,14 @@
     ],
     "require": {
         "php": ">=5.3.3",
-        "symfony/yaml": "~2.3|~3.0"
+        "symfony/yaml": "~2.3|~3.0",
+        "seld/jsonlint": "~1.4"
     },
     "require-dev": {
         "composer/composer": "1.0.*@dev",
         "phpspec/prophecy-phpunit": "~1.0",
-        "symfony/filesystem": "~2.2"
+        "symfony/filesystem": "~2.2",
+        "symfony/var-dumper": "~2.8"
     },
     "autoload": {
         "psr-4": { "Incenteev\\ParameterHandler\\": "" }