diff --git a/API.md b/API.md
index a48c650..6f431ed 100644
--- a/API.md
+++ b/API.md
@@ -706,7 +706,7 @@ finish_spying();
 
 ## PHPUnit Custom Assertions
 
-These are methods available on instances of `\Spies\TestCase`.
+These are methods available on instances of `\Spies\TestCase`, which is loaded only if PHPUnit is loaded.
 
 ### Constraints for `assertThat()`
 
diff --git a/composer.json b/composer.json
index e0c6c15..c51bcaf 100644
--- a/composer.json
+++ b/composer.json
@@ -5,12 +5,14 @@
     "keywords": ["phpunit", "mocking", "stubs", "spies", "spy"],
     "homepage": "https://github.com/sirbrillig/spies",
     "require": {
-        "php": ">=5.3.0",
+        "php": ">=5.3.0"
+    },
+    "require-dev": {
         "phpunit/phpunit": "^5.2",
         "antecedent/patchwork": "^2.0.0"
     },
     "scripts": {
-        "test": ["phpunit"]
+        "test": ["vendor/bin/phpunit"]
     },
     "license": "MIT",
     "autoload": {
diff --git a/composer.lock b/composer.lock
index e6340ec..5d05446 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,21 +4,22 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
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-    "content-hash": "6183d33165af8232ee98d15ddb6de341",
-    "packages": [
+    "hash": "48601940ddf1c348bf45cb566875348e",
+    "content-hash": "f4b4d6327e1d1f7146325b75a6da777c",
+    "packages": [],
+    "packages-dev": [
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+            "version": "2.1.5",
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                 "type": "git",
                 "url": "https://github.com/antecedent/patchwork.git",
-                "reference": "698b39d41c1786ef065b3fb3d0a82e9257c36178"
+                "reference": "ee5e6d669b9e379cff7b42c005c55e7b8c33b9d8"
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-                "reference": "698b39d41c1786ef065b3fb3d0a82e9257c36178",
+                "url": "https://api.github.com/repos/antecedent/patchwork/zipball/ee5e6d669b9e379cff7b42c005c55e7b8c33b9d8",
+                "reference": "ee5e6d669b9e379cff7b42c005c55e7b8c33b9d8",
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@@ -46,36 +47,36 @@
                 "runkit",
                 "testing"
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-            "time": "2016-08-12 18:56:30"
+            "time": "2017-09-11 13:43:30"
         },
         {
             "name": "doctrine/instantiator",
-            "version": "1.0.5",
+            "version": "1.1.0",
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                 "url": "https://github.com/doctrine/instantiator.git",
-                "reference": "8e884e78f9f0eb1329e445619e04456e64d8051d"
+                "reference": "185b8868aa9bf7159f5f953ed5afb2d7fcdc3bda"
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-                "reference": "8e884e78f9f0eb1329e445619e04456e64d8051d",
+                "url": "https://api.github.com/repos/doctrine/instantiator/zipball/185b8868aa9bf7159f5f953ed5afb2d7fcdc3bda",
+                "reference": "185b8868aa9bf7159f5f953ed5afb2d7fcdc3bda",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.3,<8.0-DEV"
+                "php": "^7.1"
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                 "athletic/athletic": "~0.1.8",
                 "ext-pdo": "*",
                 "ext-phar": "*",
-                "phpunit/phpunit": "~4.0",
-                "squizlabs/php_codesniffer": "~2.0"
+                "phpunit/phpunit": "^6.2.3",
+                "squizlabs/php_codesniffer": "^3.0.2"
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-                    "dev-master": "1.0.x-dev"
+                    "dev-master": "1.2.x-dev"
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@@ -100,41 +101,44 @@
                 "constructor",
                 "instantiate"
             ],
-            "time": "2015-06-14 21:17:01"
+            "time": "2017-07-22 11:58:36"
         },
         {
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-            "version": "1.5.1",
+            "version": "1.7.0",
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                 "url": "https://github.com/myclabs/DeepCopy.git",
-                "reference": "a8773992b362b58498eed24bf85005f363c34771"
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+                "url": "https://api.github.com/repos/myclabs/DeepCopy/zipball/3b8a3a99ba1f6a3952ac2747d989303cbd6b7a3e",
+                "reference": "3b8a3a99ba1f6a3952ac2747d989303cbd6b7a3e",
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             "require": {
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+                "php": "^5.6 || ^7.0"
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             "require-dev": {
-                "doctrine/collections": "1.*",
-                "phpunit/phpunit": "~4.1"
+                "doctrine/collections": "^1.0",
+                "doctrine/common": "^2.6",
+                "phpunit/phpunit": "^4.1"
             },
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             "autoload": {
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                     "DeepCopy\\": "src/DeepCopy/"
-                }
+                },
+                "files": [
+                    "src/DeepCopy/deep_copy.php"
+                ]
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             "notification-url": "https://packagist.org/downloads/",
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-            "homepage": "https://github.com/myclabs/DeepCopy",
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@@ -142,20 +146,20 @@
                 "object",
                 "object graph"
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-            "time": "2015-11-20 12:04:31"
+            "time": "2017-10-19 19:58:43"
         },
         {
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-            "version": "1.0",
+            "version": "1.0.1",
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                 "url": "https://github.com/phpDocumentor/ReflectionCommon.git",
-                "reference": "144c307535e82c8fdcaacbcfc1d6d8eeb896687c"
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@@ -196,26 +200,26 @@
                 "reflection",
                 "static analysis"
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-            "time": "2015-12-27 11:43:31"
+            "time": "2017-09-11 18:02:19"
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-            "version": "3.1.0",
+            "version": "4.1.1",
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-                "reference": "9270140b940ff02e58ec577c237274e92cd40cdd"
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-                "reference": "9270140b940ff02e58ec577c237274e92cd40cdd",
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+                "phpdocumentor/type-resolver": "^0.4.0",
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@@ -241,24 +245,24 @@
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             "description": "With this component, a library can provide support for annotations via DocBlocks or otherwise retrieve information that is embedded in a DocBlock.",
-            "time": "2016-06-10 09:48:41"
+            "time": "2017-08-30 18:51:59"
         },
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-            "version": "0.2",
+            "version": "0.4.0",
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                 "url": "https://github.com/phpDocumentor/TypeResolver.git",
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+                "php": "^5.5 || ^7.0",
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@@ -288,36 +292,37 @@
                     "email": "me@mikevanriel.com"
                 }
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-            "time": "2016-06-10 07:14:17"
+            "time": "2017-07-14 14:27:02"
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                 "php": "^5.3|^7.0",
-                "phpdocumentor/reflection-docblock": "^2.0|^3.0.2",
-                "sebastian/comparator": "^1.1",
-                "sebastian/recursion-context": "^1.0"
+                "phpdocumentor/reflection-docblock": "^2.0|^3.0.2|^4.0",
+                "sebastian/comparator": "^1.1|^2.0",
+                "sebastian/recursion-context": "^1.0|^2.0|^3.0"
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@@ -350,39 +355,39 @@
                 "spy",
                 "stub"
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-            "time": "2016-06-07 08:13:47"
+            "time": "2017-09-04 11:05:03"
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+                "ext-xmlwriter": "*",
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-                "phpunit/php-text-template": "~1.2",
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-                "sebastian/code-unit-reverse-lookup": "~1.0",
+                "phpunit/php-file-iterator": "^1.3",
+                "phpunit/php-text-template": "^1.2",
+                "phpunit/php-token-stream": "^1.4.2 || ^2.0",
+                "sebastian/code-unit-reverse-lookup": "^1.0",
                 "sebastian/environment": "^1.3.2 || ^2.0",
-                "sebastian/version": "~1.0|~2.0"
+                "sebastian/version": "^1.0 || ^2.0"
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             "require-dev": {
-                "ext-xdebug": ">=2.1.4",
-                "phpunit/phpunit": "^5.4"
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-                "ext-xdebug": ">=2.4.0",
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@@ -413,20 +418,20 @@
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                 "xunit"
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-            "time": "2016-07-26 14:39:29"
+            "time": "2017-04-02 07:44:40"
         },
         {
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-            "version": "1.4.1",
+            "version": "1.4.2",
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@@ -460,7 +465,7 @@
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@@ -505,25 +510,30 @@
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@@ -545,33 +555,33 @@
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-                "sebastian/object-enumerator": "~1.0",
+                "sebastian/comparator": "^1.2.4",
+                "sebastian/diff": "^1.4.3",
+                "sebastian/environment": "^1.3.4 || ^2.0",
+                "sebastian/exporter": "~2.0",
+                "sebastian/global-state": "^1.1",
+                "sebastian/object-enumerator": "~2.0",
                 "sebastian/resource-operations": "~1.0",
-                "sebastian/version": "~1.0|~2.0",
+                "sebastian/version": "~1.0.3|~2.0",
                 "symfony/yaml": "~2.1|~3.0"
             },
             "conflict": {
                 "phpdocumentor/reflection-docblock": "3.0.2"
             },
+            "require-dev": {
+                "ext-pdo": "*"
+            },
             "suggest": {
+                "ext-xdebug": "*",
                 "phpunit/php-invoker": "~1.1"
             },
             "bin": [
@@ -646,7 +660,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "5.5.x-dev"
+                    "dev-master": "5.7.x-dev"
                 }
             },
             "autoload": {
@@ -672,27 +686,27 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2016-08-18 11:10:44"
+            "time": "2017-10-15 06:13:55"
         },
         {
             "name": "phpunit/phpunit-mock-objects",
-            "version": "3.2.4",
+            "version": "3.4.4",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit-mock-objects.git",
-                "reference": "4e83390f64e7ce04fcaec2ce95cd72823b431d19"
+                "reference": "a23b761686d50a560cc56233b9ecf49597cc9118"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit-mock-objects/zipball/4e83390f64e7ce04fcaec2ce95cd72823b431d19",
-                "reference": "4e83390f64e7ce04fcaec2ce95cd72823b431d19",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit-mock-objects/zipball/a23b761686d50a560cc56233b9ecf49597cc9118",
+                "reference": "a23b761686d50a560cc56233b9ecf49597cc9118",
                 "shasum": ""
             },
             "require": {
                 "doctrine/instantiator": "^1.0.2",
                 "php": "^5.6 || ^7.0",
                 "phpunit/php-text-template": "^1.2",
-                "sebastian/exporter": "^1.2"
+                "sebastian/exporter": "^1.2 || ^2.0"
             },
             "conflict": {
                 "phpunit/phpunit": "<5.4.0"
@@ -731,27 +745,27 @@
                 "mock",
                 "xunit"
             ],
-            "time": "2016-08-17 09:33:51"
+            "time": "2017-06-30 09:13:00"
         },
         {
             "name": "sebastian/code-unit-reverse-lookup",
-            "version": "1.0.0",
+            "version": "1.0.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/code-unit-reverse-lookup.git",
-                "reference": "c36f5e7cfce482fde5bf8d10d41a53591e0198fe"
+                "reference": "4419fcdb5eabb9caa61a27c7a1db532a6b55dd18"
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             "dist": {
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-                "url": "https://api.github.com/repos/sebastianbergmann/code-unit-reverse-lookup/zipball/c36f5e7cfce482fde5bf8d10d41a53591e0198fe",
-                "reference": "c36f5e7cfce482fde5bf8d10d41a53591e0198fe",
+                "url": "https://api.github.com/repos/sebastianbergmann/code-unit-reverse-lookup/zipball/4419fcdb5eabb9caa61a27c7a1db532a6b55dd18",
+                "reference": "4419fcdb5eabb9caa61a27c7a1db532a6b55dd18",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.6"
+                "php": "^5.6 || ^7.0"
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             "require-dev": {
-                "phpunit/phpunit": "~5"
+                "phpunit/phpunit": "^5.7 || ^6.0"
             },
             "type": "library",
             "extra": {
@@ -776,26 +790,26 @@
             ],
             "description": "Looks up which function or method a line of code belongs to",
             "homepage": "https://github.com/sebastianbergmann/code-unit-reverse-lookup/",
-            "time": "2016-02-13 06:45:14"
+            "time": "2017-03-04 06:30:41"
         },
         {
             "name": "sebastian/comparator",
-            "version": "1.2.0",
+            "version": "1.2.4",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/comparator.git",
-                "reference": "937efb279bd37a375bcadf584dec0726f84dbf22"
+                "reference": "2b7424b55f5047b47ac6e5ccb20b2aea4011d9be"
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-                "reference": "937efb279bd37a375bcadf584dec0726f84dbf22",
+                "url": "https://api.github.com/repos/sebastianbergmann/comparator/zipball/2b7424b55f5047b47ac6e5ccb20b2aea4011d9be",
+                "reference": "2b7424b55f5047b47ac6e5ccb20b2aea4011d9be",
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             "require": {
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                 "sebastian/diff": "~1.2",
-                "sebastian/exporter": "~1.2"
+                "sebastian/exporter": "~1.2 || ~2.0"
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             "require-dev": {
                 "phpunit/phpunit": "~4.4"
@@ -840,27 +854,27 @@
                 "compare",
                 "equality"
             ],
-            "time": "2015-07-26 15:48:44"
+            "time": "2017-01-29 09:50:25"
         },
         {
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-            "version": "1.4.1",
+            "version": "1.4.3",
             "source": {
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                 "url": "https://github.com/sebastianbergmann/diff.git",
-                "reference": "13edfd8706462032c2f52b4b862974dd46b71c9e"
+                "reference": "7f066a26a962dbe58ddea9f72a4e82874a3975a4"
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-                "reference": "13edfd8706462032c2f52b4b862974dd46b71c9e",
+                "url": "https://api.github.com/repos/sebastianbergmann/diff/zipball/7f066a26a962dbe58ddea9f72a4e82874a3975a4",
+                "reference": "7f066a26a962dbe58ddea9f72a4e82874a3975a4",
                 "shasum": ""
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             "require": {
-                "php": ">=5.3.3"
+                "php": "^5.3.3 || ^7.0"
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             "require-dev": {
-                "phpunit/phpunit": "~4.8"
+                "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.0"
             },
             "type": "library",
             "extra": {
@@ -892,32 +906,32 @@
             "keywords": [
                 "diff"
             ],
-            "time": "2015-12-08 07:14:41"
+            "time": "2017-05-22 07:24:03"
         },
         {
             "name": "sebastian/environment",
-            "version": "1.3.8",
+            "version": "2.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/environment.git",
-                "reference": "be2c607e43ce4c89ecd60e75c6a85c126e754aea"
+                "reference": "5795ffe5dc5b02460c3e34222fee8cbe245d8fac"
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-                "url": "https://api.github.com/repos/sebastianbergmann/environment/zipball/be2c607e43ce4c89ecd60e75c6a85c126e754aea",
-                "reference": "be2c607e43ce4c89ecd60e75c6a85c126e754aea",
+                "url": "https://api.github.com/repos/sebastianbergmann/environment/zipball/5795ffe5dc5b02460c3e34222fee8cbe245d8fac",
+                "reference": "5795ffe5dc5b02460c3e34222fee8cbe245d8fac",
                 "shasum": ""
             },
             "require": {
-                "php": "^5.3.3 || ^7.0"
+                "php": "^5.6 || ^7.0"
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             "require-dev": {
-                "phpunit/phpunit": "^4.8 || ^5.0"
+                "phpunit/phpunit": "^5.0"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.3.x-dev"
+                    "dev-master": "2.0.x-dev"
                 }
             },
             "autoload": {
@@ -942,25 +956,25 @@
                 "environment",
                 "hhvm"
             ],
-            "time": "2016-08-18 05:49:44"
+            "time": "2016-11-26 07:53:53"
         },
         {
             "name": "sebastian/exporter",
-            "version": "1.2.2",
+            "version": "2.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/exporter.git",
-                "reference": "42c4c2eec485ee3e159ec9884f95b431287edde4"
+                "reference": "ce474bdd1a34744d7ac5d6aad3a46d48d9bac4c4"
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             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/exporter/zipball/42c4c2eec485ee3e159ec9884f95b431287edde4",
-                "reference": "42c4c2eec485ee3e159ec9884f95b431287edde4",
+                "url": "https://api.github.com/repos/sebastianbergmann/exporter/zipball/ce474bdd1a34744d7ac5d6aad3a46d48d9bac4c4",
+                "reference": "ce474bdd1a34744d7ac5d6aad3a46d48d9bac4c4",
                 "shasum": ""
             },
             "require": {
                 "php": ">=5.3.3",
-                "sebastian/recursion-context": "~1.0"
+                "sebastian/recursion-context": "~2.0"
             },
             "require-dev": {
                 "ext-mbstring": "*",
@@ -969,7 +983,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.3.x-dev"
+                    "dev-master": "2.0.x-dev"
                 }
             },
             "autoload": {
@@ -1009,7 +1023,7 @@
                 "export",
                 "exporter"
             ],
-            "time": "2016-06-17 09:04:28"
+            "time": "2016-11-19 08:54:04"
         },
         {
             "name": "sebastian/global-state",
@@ -1064,21 +1078,21 @@
         },
         {
             "name": "sebastian/object-enumerator",
-            "version": "1.0.0",
+            "version": "2.0.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/object-enumerator.git",
-                "reference": "d4ca2fb70344987502567bc50081c03e6192fb26"
+                "reference": "1311872ac850040a79c3c058bea3e22d0f09cbb7"
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             "dist": {
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-                "url": "https://api.github.com/repos/sebastianbergmann/object-enumerator/zipball/d4ca2fb70344987502567bc50081c03e6192fb26",
-                "reference": "d4ca2fb70344987502567bc50081c03e6192fb26",
+                "url": "https://api.github.com/repos/sebastianbergmann/object-enumerator/zipball/1311872ac850040a79c3c058bea3e22d0f09cbb7",
+                "reference": "1311872ac850040a79c3c058bea3e22d0f09cbb7",
                 "shasum": ""
             },
             "require": {
                 "php": ">=5.6",
-                "sebastian/recursion-context": "~1.0"
+                "sebastian/recursion-context": "~2.0"
             },
             "require-dev": {
                 "phpunit/phpunit": "~5"
@@ -1086,7 +1100,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.0.x-dev"
+                    "dev-master": "2.0.x-dev"
                 }
             },
             "autoload": {
@@ -1106,20 +1120,20 @@
             ],
             "description": "Traverses array structures and object graphs to enumerate all referenced objects",
             "homepage": "https://github.com/sebastianbergmann/object-enumerator/",
-            "time": "2016-01-28 13:25:10"
+            "time": "2017-02-18 15:18:39"
         },
         {
             "name": "sebastian/recursion-context",
-            "version": "1.0.2",
+            "version": "2.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/recursion-context.git",
-                "reference": "913401df809e99e4f47b27cdd781f4a258d58791"
+                "reference": "2c3ba150cbec723aa057506e73a8d33bdb286c9a"
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-                "reference": "913401df809e99e4f47b27cdd781f4a258d58791",
+                "url": "https://api.github.com/repos/sebastianbergmann/recursion-context/zipball/2c3ba150cbec723aa057506e73a8d33bdb286c9a",
+                "reference": "2c3ba150cbec723aa057506e73a8d33bdb286c9a",
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             "require": {
@@ -1131,7 +1145,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.0.x-dev"
+                    "dev-master": "2.0.x-dev"
                 }
             },
             "autoload": {
@@ -1159,7 +1173,7 @@
             ],
             "description": "Provides functionality to recursively process PHP variables",
             "homepage": "http://www.github.com/sebastianbergmann/recursion-context",
-            "time": "2015-11-11 19:50:13"
+            "time": "2016-11-19 07:33:16"
         },
         {
             "name": "sebastian/resource-operations",
@@ -1205,16 +1219,16 @@
         },
         {
             "name": "sebastian/version",
-            "version": "2.0.0",
+            "version": "2.0.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/version.git",
-                "reference": "c829badbd8fdf16a0bad8aa7fa7971c029f1b9c5"
+                "reference": "99732be0ddb3361e16ad77b68ba41efc8e979019"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/version/zipball/c829badbd8fdf16a0bad8aa7fa7971c029f1b9c5",
-                "reference": "c829badbd8fdf16a0bad8aa7fa7971c029f1b9c5",
+                "url": "https://api.github.com/repos/sebastianbergmann/version/zipball/99732be0ddb3361e16ad77b68ba41efc8e979019",
+                "reference": "99732be0ddb3361e16ad77b68ba41efc8e979019",
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             },
             "require": {
@@ -1244,29 +1258,35 @@
             ],
             "description": "Library that helps with managing the version number of Git-hosted PHP projects",
             "homepage": "https://github.com/sebastianbergmann/version",
-            "time": "2016-02-04 12:56:52"
+            "time": "2016-10-03 07:35:21"
         },
         {
             "name": "symfony/yaml",
-            "version": "v3.1.3",
+            "version": "v3.3.10",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/yaml.git",
-                "reference": "1819adf2066880c7967df7180f4f662b6f0567ac"
+                "reference": "8c7bf1e7d5d6b05a690b715729cb4cd0c0a99c46"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/yaml/zipball/1819adf2066880c7967df7180f4f662b6f0567ac",
-                "reference": "1819adf2066880c7967df7180f4f662b6f0567ac",
+                "url": "https://api.github.com/repos/symfony/yaml/zipball/8c7bf1e7d5d6b05a690b715729cb4cd0c0a99c46",
+                "reference": "8c7bf1e7d5d6b05a690b715729cb4cd0c0a99c46",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.5.9"
+                "php": "^5.5.9|>=7.0.8"
+            },
+            "require-dev": {
+                "symfony/console": "~2.8|~3.0"
+            },
+            "suggest": {
+                "symfony/console": "For validating YAML files using the lint command"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "3.1-dev"
+                    "dev-master": "3.3-dev"
                 }
             },
             "autoload": {
@@ -1293,24 +1313,24 @@
             ],
             "description": "Symfony Yaml Component",
             "homepage": "https://symfony.com",
-            "time": "2016-07-17 14:02:08"
+            "time": "2017-10-05 14:43:42"
         },
         {
             "name": "webmozart/assert",
-            "version": "1.1.0",
+            "version": "1.2.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/webmozart/assert.git",
-                "reference": "bb2d123231c095735130cc8f6d31385a44c7b308"
+                "reference": "2db61e59ff05fe5126d152bd0655c9ea113e550f"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/webmozart/assert/zipball/bb2d123231c095735130cc8f6d31385a44c7b308",
-                "reference": "bb2d123231c095735130cc8f6d31385a44c7b308",
+                "url": "https://api.github.com/repos/webmozart/assert/zipball/2db61e59ff05fe5126d152bd0655c9ea113e550f",
+                "reference": "2db61e59ff05fe5126d152bd0655c9ea113e550f",
                 "shasum": ""
             },
             "require": {
-                "php": "^5.3.3|^7.0"
+                "php": "^5.3.3 || ^7.0"
             },
             "require-dev": {
                 "phpunit/phpunit": "^4.6",
@@ -1319,7 +1339,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "1.2-dev"
+                    "dev-master": "1.3-dev"
                 }
             },
             "autoload": {
@@ -1343,10 +1363,9 @@
                 "check",
                 "validate"
             ],
-            "time": "2016-08-09 15:02:57"
+            "time": "2016-11-23 20:04:58"
         }
     ],
-    "packages-dev": [],
     "aliases": [],
     "minimum-stability": "stable",
     "stability-flags": [],
diff --git a/src/Spies/TestCase.php b/src/Spies/TestCase.php
index 07733f5..4daefec 100644
--- a/src/Spies/TestCase.php
+++ b/src/Spies/TestCase.php
@@ -1,6 +1,10 @@
 <?php
 namespace Spies;
 
+if ( ! class_exists( '\PHPUnit_Framework_TestCase' ) ) {
+	return;
+}
+
 abstract class TestCase extends \PHPUnit_Framework_TestCase {
 
 	public static function wasCalled() {