diff --git a/composer.json b/composer.json
index 9ad5d4a..50e79b3 100644
--- a/composer.json
+++ b/composer.json
@@ -14,11 +14,13 @@
         "ext-json": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "4.8.36"
+        "phpunit/phpunit": "4.8.36",
+        "mikey179/vfsStream": "^1.6"
     },
     "autoload": {
         "psr-4": {
-            "HaydenPierce\\ClassFinder\\": "src/"
+            "HaydenPierce\\ClassFinder\\": "src/",
+            "HaydenPierce\\ClassFinder\\UnitTest\\": "test/unit"
         }
     }
 }
diff --git a/composer.lock b/composer.lock
index 315301a..8f5e76d 100644
--- a/composer.lock
+++ b/composer.lock
@@ -1,10 +1,10 @@
 {
     "_readme": [
         "This file locks the dependencies of your project to a known state",
-        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "content-hash": "3b2eddc1d92027b147b147fcc217e83c",
+    "content-hash": "f3f590855bb74189d0c049ef88784132",
     "packages": [],
     "packages-dev": [
         {
@@ -62,38 +62,139 @@
             "time": "2015-06-14T21:17:01+00:00"
         },
         {
-            "name": "phpdocumentor/reflection-docblock",
-            "version": "2.0.5",
+            "name": "mikey179/vfsStream",
+            "version": "v1.6.5",
             "source": {
                 "type": "git",
-                "url": "https://github.com/phpDocumentor/ReflectionDocBlock.git",
-                "reference": "e6a969a640b00d8daa3c66518b0405fb41ae0c4b"
+                "url": "https://github.com/mikey179/vfsStream.git",
+                "reference": "d5fec95f541d4d71c4823bb5e30cf9b9e5b96145"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpDocumentor/ReflectionDocBlock/zipball/e6a969a640b00d8daa3c66518b0405fb41ae0c4b",
-                "reference": "e6a969a640b00d8daa3c66518b0405fb41ae0c4b",
+                "url": "https://api.github.com/repos/mikey179/vfsStream/zipball/d5fec95f541d4d71c4823bb5e30cf9b9e5b96145",
+                "reference": "d5fec95f541d4d71c4823bb5e30cf9b9e5b96145",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.3.3"
+                "php": ">=5.3.0"
             },
             "require-dev": {
-                "phpunit/phpunit": "~4.0"
-            },
-            "suggest": {
-                "dflydev/markdown": "~1.0",
-                "erusev/parsedown": "~1.0"
+                "phpunit/phpunit": "~4.5"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "2.0.x-dev"
+                    "dev-master": "1.6.x-dev"
                 }
             },
             "autoload": {
                 "psr-0": {
-                    "phpDocumentor": [
+                    "org\\bovigo\\vfs\\": "src/main/php"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause"
+            ],
+            "authors": [
+                {
+                    "name": "Frank Kleine",
+                    "homepage": "http://frankkleine.de/",
+                    "role": "Developer"
+                }
+            ],
+            "description": "Virtual file system to mock the real file system in unit tests.",
+            "homepage": "http://vfs.bovigo.org/",
+            "time": "2017-08-01T08:02:14+00:00"
+        },
+        {
+            "name": "phpdocumentor/reflection-common",
+            "version": "1.0.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpDocumentor/ReflectionCommon.git",
+                "reference": "21bdeb5f65d7ebf9f43b1b25d404f87deab5bfb6"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpDocumentor/ReflectionCommon/zipball/21bdeb5f65d7ebf9f43b1b25d404f87deab5bfb6",
+                "reference": "21bdeb5f65d7ebf9f43b1b25d404f87deab5bfb6",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.5"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.6"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "phpDocumentor\\Reflection\\": [
+                        "src"
+                    ]
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Jaap van Otterdijk",
+                    "email": "opensource@ijaap.nl"
+                }
+            ],
+            "description": "Common reflection classes used by phpdocumentor to reflect the code structure",
+            "homepage": "http://www.phpdoc.org",
+            "keywords": [
+                "FQSEN",
+                "phpDocumentor",
+                "phpdoc",
+                "reflection",
+                "static analysis"
+            ],
+            "time": "2017-09-11T18:02:19+00:00"
+        },
+        {
+            "name": "phpdocumentor/reflection-docblock",
+            "version": "4.3.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpDocumentor/ReflectionDocBlock.git",
+                "reference": "94fd0001232e47129dd3504189fa1c7225010d08"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpDocumentor/ReflectionDocBlock/zipball/94fd0001232e47129dd3504189fa1c7225010d08",
+                "reference": "94fd0001232e47129dd3504189fa1c7225010d08",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.0",
+                "phpdocumentor/reflection-common": "^1.0.0",
+                "phpdocumentor/type-resolver": "^0.4.0",
+                "webmozart/assert": "^1.0"
+            },
+            "require-dev": {
+                "doctrine/instantiator": "~1.0.5",
+                "mockery/mockery": "^1.0",
+                "phpunit/phpunit": "^6.4"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "4.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "phpDocumentor\\Reflection\\": [
                         "src/"
                     ]
                 }
@@ -105,10 +206,58 @@
             "authors": [
                 {
                     "name": "Mike van Riel",
-                    "email": "mike.vanriel@naenius.com"
+                    "email": "me@mikevanriel.com"
                 }
             ],
-            "time": "2016-01-25T08:17:30+00:00"
+            "description": "With this component, a library can provide support for annotations via DocBlocks or otherwise retrieve information that is embedded in a DocBlock.",
+            "time": "2017-11-30T07:14:17+00:00"
+        },
+        {
+            "name": "phpdocumentor/type-resolver",
+            "version": "0.4.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpDocumentor/TypeResolver.git",
+                "reference": "9c977708995954784726e25d0cd1dddf4e65b0f7"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpDocumentor/TypeResolver/zipball/9c977708995954784726e25d0cd1dddf4e65b0f7",
+                "reference": "9c977708995954784726e25d0cd1dddf4e65b0f7",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.5 || ^7.0",
+                "phpdocumentor/reflection-common": "^1.0"
+            },
+            "require-dev": {
+                "mockery/mockery": "^0.9.4",
+                "phpunit/phpunit": "^5.2||^4.8.24"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "phpDocumentor\\Reflection\\": [
+                        "src/"
+                    ]
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Mike van Riel",
+                    "email": "me@mikevanriel.com"
+                }
+            ],
+            "time": "2017-07-14T14:27:02+00:00"
         },
         {
             "name": "phpspec/prophecy",
@@ -981,26 +1130,35 @@
         },
         {
             "name": "symfony/yaml",
-            "version": "v2.8.45",
+            "version": "v3.4.15",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/yaml.git",
-                "reference": "fbf876678e29dc634430dcf0096e216eb0004467"
+                "reference": "c2f4812ead9f847cb69e90917ca7502e6892d6b8"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/yaml/zipball/fbf876678e29dc634430dcf0096e216eb0004467",
-                "reference": "fbf876678e29dc634430dcf0096e216eb0004467",
+                "url": "https://api.github.com/repos/symfony/yaml/zipball/c2f4812ead9f847cb69e90917ca7502e6892d6b8",
+                "reference": "c2f4812ead9f847cb69e90917ca7502e6892d6b8",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.3.9",
+                "php": "^5.5.9|>=7.0.8",
                 "symfony/polyfill-ctype": "~1.8"
             },
+            "conflict": {
+                "symfony/console": "<3.4"
+            },
+            "require-dev": {
+                "symfony/console": "~3.4|~4.0"
+            },
+            "suggest": {
+                "symfony/console": "For validating YAML files using the lint command"
+            },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "2.8-dev"
+                    "dev-master": "3.4-dev"
                 }
             },
             "autoload": {
@@ -1027,7 +1185,57 @@
             ],
             "description": "Symfony Yaml Component",
             "homepage": "https://symfony.com",
-            "time": "2018-07-26T09:03:18+00:00"
+            "time": "2018-08-10T07:34:36+00:00"
+        },
+        {
+            "name": "webmozart/assert",
+            "version": "1.3.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/webmozart/assert.git",
+                "reference": "0df1908962e7a3071564e857d86874dad1ef204a"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/webmozart/assert/zipball/0df1908962e7a3071564e857d86874dad1ef204a",
+                "reference": "0df1908962e7a3071564e857d86874dad1ef204a",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^5.3.3 || ^7.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^4.6",
+                "sebastian/version": "^1.0.1"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.3-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Webmozart\\Assert\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Bernhard Schussek",
+                    "email": "bschussek@gmail.com"
+                }
+            ],
+            "description": "Assertions to validate method input/output with nice error messages.",
+            "keywords": [
+                "assert",
+                "check",
+                "validate"
+            ],
+            "time": "2018-01-29T19:49:41+00:00"
         }
     ],
     "aliases": [],
@@ -1035,6 +1243,9 @@
     "stability-flags": [],
     "prefer-stable": false,
     "prefer-lowest": false,
-    "platform": [],
+    "platform": {
+        "php": ">=5.3",
+        "ext-json": "*"
+    },
     "platform-dev": []
 }
diff --git a/phpunit.xml b/phpunit.xml
index 673aa5d..458d018 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -13,6 +13,7 @@
         </testsuite>
         <testsuite name="psr4">
             <file>test/app1/src/PSR4Test.php</file>
+            <directory>test/unit/PSR4</directory>
         </testsuite>
         <testsuite name="classmap">
             <file>test/app1/src/ClassmapTest.php</file>
diff --git a/test/unit/PSR4/PSR4NamespaceTest.php b/test/unit/PSR4/PSR4NamespaceTest.php
new file mode 100644
index 0000000..a3bb159
--- /dev/null
+++ b/test/unit/PSR4/PSR4NamespaceTest.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace HaydenPierce\ClassFinder\UnitTest;
+
+use HaydenPierce\ClassFinder\PSR4\PSR4Namespace;
+use org\bovigo\vfs\vfsStream;
+use org\bovigo\vfs\vfsStreamDirectory;
+
+class PSR4NamespaceTest extends \PHPUnit_Framework_TestCase
+{
+    /** @var vfsStreamDirectory */
+    private $root;
+
+    public function setUp()
+    {
+        $structure = $this->getTestStructure();
+        $this->root = vfsStream::setup('root', null, $structure);
+    }
+
+    public function getTestStructure()
+    {
+        return array(
+            'Baz' => array(
+                'Foo' => array(
+                    'Fooa.php' => $this->getClassFileContents('PSR4\\Foo', 'Fooa'),
+                    'Foob.php' => $this->getClassFileContents('PSR4\\Foo', 'Foob')
+                ),
+                'Bar.php' => $this->getClassFileContents('PSR4', 'Bar'),
+                'Barb.php' => $this->getClassFileContents('PSR4', 'Barb')
+            )
+        );
+    }
+
+    public function getClassFileContents($namespace, $className)
+    {
+        $template = <<<EOL
+<?php 
+
+namespace %s
+
+class %s
+{
+}
+EOL;
+
+        return sprintf($template, $namespace, $className);
+    }
+
+    public function testCountMatchingNamespaceSegments()
+    {
+        $namespace = new PSR4Namespace('MyPSR4Root\\Foot\\', $this->root->getChild('Baz')->path());
+
+        $this->assertEquals($namespace->countMatchingNamespaceSegments('MyPSR4Root\\Foot'), 2);
+        $this->assertEquals($namespace->countMatchingNamespaceSegments('MyPSR4Root'), 1);
+        $this->assertEquals($namespace->countMatchingNamespaceSegments('MyPSR4Root\\Foot\\Baz\\Foo'), 3);
+        $this->assertEquals($namespace->countMatchingNamespaceSegments('MyPSR4Root\\Foot\\Baz'), 3);
+        $this->assertEquals($namespace->countMatchingNamespaceSegments('Cactus'), 0);
+        $this->assertEquals($namespace->countMatchingNamespaceSegments('Cactus\\Foot'), 0);
+    }
+}