diff --git a/composer.lock b/composer.lock
index 02fac6b..d582328 100644
--- a/composer.lock
+++ b/composer.lock
@@ -362,23 +362,23 @@
         },
         {
             "name": "phpspec/prophecy",
-            "version": "1.7.5",
+            "version": "1.7.6",
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                 "url": "https://github.com/phpspec/prophecy.git",
-                "reference": "dfd6be44111a7c41c2e884a336cc4f461b3b2401"
+                "reference": "33a7e3c4fda54e912ff6338c48823bd5c0f0b712"
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-                "reference": "dfd6be44111a7c41c2e884a336cc4f461b3b2401",
+                "url": "https://api.github.com/repos/phpspec/prophecy/zipball/33a7e3c4fda54e912ff6338c48823bd5c0f0b712",
+                "reference": "33a7e3c4fda54e912ff6338c48823bd5c0f0b712",
                 "shasum": ""
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             "require": {
                 "doctrine/instantiator": "^1.0.2",
                 "php": "^5.3|^7.0",
                 "phpdocumentor/reflection-docblock": "^2.0|^3.0.2|^4.0",
-                "sebastian/comparator": "^1.1|^2.0",
+                "sebastian/comparator": "^1.1|^2.0|^3.0",
                 "sebastian/recursion-context": "^1.0|^2.0|^3.0"
             },
             "require-dev": {
@@ -421,20 +421,20 @@
                 "spy",
                 "stub"
             ],
-            "time": "2018-02-19T10:16:54+00:00"
+            "time": "2018-04-18T13:57:24+00:00"
         },
         {
             "name": "phpunit/php-code-coverage",
-            "version": "6.0.1",
+            "version": "6.0.4",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/php-code-coverage.git",
-                "reference": "f8ca4b604baf23dab89d87773c28cc07405189ba"
+                "reference": "52187754b0eed0b8159f62a6fa30073327e8c2ca"
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-                "url": "https://api.github.com/repos/sebastianbergmann/php-code-coverage/zipball/f8ca4b604baf23dab89d87773c28cc07405189ba",
-                "reference": "f8ca4b604baf23dab89d87773c28cc07405189ba",
+                "url": "https://api.github.com/repos/sebastianbergmann/php-code-coverage/zipball/52187754b0eed0b8159f62a6fa30073327e8c2ca",
+                "reference": "52187754b0eed0b8159f62a6fa30073327e8c2ca",
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             "require": {
@@ -445,7 +445,7 @@
                 "phpunit/php-text-template": "^1.2.1",
                 "phpunit/php-token-stream": "^3.0",
                 "sebastian/code-unit-reverse-lookup": "^1.0.1",
-                "sebastian/environment": "^3.0",
+                "sebastian/environment": "^3.1",
                 "sebastian/version": "^2.0.1",
                 "theseer/tokenizer": "^1.1"
             },
@@ -484,7 +484,7 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2018-02-02T07:01:41+00:00"
+            "time": "2018-04-29T14:59:09+00:00"
         },
         {
             "name": "phpunit/php-file-iterator",
@@ -674,16 +674,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "7.0.1",
+            "version": "7.1.5",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "316555dbd0ed4097bbdd17c65ab416bf27a472e9"
+                "reference": "ca64dba53b88aba6af32aebc6b388068db95c435"
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-                "reference": "316555dbd0ed4097bbdd17c65ab416bf27a472e9",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/ca64dba53b88aba6af32aebc6b388068db95c435",
+                "reference": "ca64dba53b88aba6af32aebc6b388068db95c435",
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             "require": {
@@ -697,12 +697,12 @@
                 "phar-io/version": "^1.0",
                 "php": "^7.1",
                 "phpspec/prophecy": "^1.7",
-                "phpunit/php-code-coverage": "^6.0",
+                "phpunit/php-code-coverage": "^6.0.1",
                 "phpunit/php-file-iterator": "^1.4.3",
                 "phpunit/php-text-template": "^1.2.1",
                 "phpunit/php-timer": "^2.0",
-                "phpunit/phpunit-mock-objects": "^6.0",
-                "sebastian/comparator": "^2.1",
+                "phpunit/phpunit-mock-objects": "^6.1.1",
+                "sebastian/comparator": "^3.0",
                 "sebastian/diff": "^3.0",
                 "sebastian/environment": "^3.1",
                 "sebastian/exporter": "^3.1",
@@ -724,7 +724,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "7.0-dev"
+                    "dev-master": "7.1-dev"
                 }
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             "autoload": {
@@ -750,20 +750,20 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2018-02-13T06:08:08+00:00"
+            "time": "2018-04-29T15:09:19+00:00"
         },
         {
             "name": "phpunit/phpunit-mock-objects",
-            "version": "6.0.1",
+            "version": "6.1.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit-mock-objects.git",
-                "reference": "e3249dedc2d99259ccae6affbc2684eac37c2e53"
+                "reference": "70c740bde8fd9ea9ea295be1cd875dd7b267e157"
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-                "reference": "e3249dedc2d99259ccae6affbc2684eac37c2e53",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit-mock-objects/zipball/70c740bde8fd9ea9ea295be1cd875dd7b267e157",
+                "reference": "70c740bde8fd9ea9ea295be1cd875dd7b267e157",
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             "require": {
@@ -781,7 +781,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "6.0.x-dev"
+                    "dev-master": "6.1-dev"
                 }
             },
             "autoload": {
@@ -806,7 +806,7 @@
                 "mock",
                 "xunit"
             ],
-            "time": "2018-02-15T05:27:38+00:00"
+            "time": "2018-04-11T04:50:36+00:00"
         },
         {
             "name": "sebastian/code-unit-reverse-lookup",
@@ -855,30 +855,30 @@
         },
         {
             "name": "sebastian/comparator",
-            "version": "2.1.3",
+            "version": "3.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/comparator.git",
-                "reference": "34369daee48eafb2651bea869b4b15d75ccc35f9"
+                "reference": "ed5fd2281113729f1ebcc64d101ad66028aeb3d5"
             },
             "dist": {
                 "type": "zip",
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-                "reference": "34369daee48eafb2651bea869b4b15d75ccc35f9",
+                "url": "https://api.github.com/repos/sebastianbergmann/comparator/zipball/ed5fd2281113729f1ebcc64d101ad66028aeb3d5",
+                "reference": "ed5fd2281113729f1ebcc64d101ad66028aeb3d5",
                 "shasum": ""
             },
             "require": {
-                "php": "^7.0",
-                "sebastian/diff": "^2.0 || ^3.0",
+                "php": "^7.1",
+                "sebastian/diff": "^3.0",
                 "sebastian/exporter": "^3.1"
             },
             "require-dev": {
-                "phpunit/phpunit": "^6.4"
+                "phpunit/phpunit": "^7.1"
             },
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "2.1.x-dev"
+                    "dev-master": "3.0-dev"
                 }
             },
             "autoload": {
@@ -915,7 +915,7 @@
                 "compare",
                 "equality"
             ],
-            "time": "2018-02-01T13:46:46+00:00"
+            "time": "2018-04-18T13:33:00+00:00"
         },
         {
             "name": "sebastian/diff",
diff --git a/src/Printer.php b/src/Printer.php
index d2ce349..bf8b053 100644
--- a/src/Printer.php
+++ b/src/Printer.php
@@ -36,7 +36,7 @@ class Printer extends ResultPrinter
     /**
      * {@inheritdoc}
      */
-    protected function writeProgress($progress) : void
+    protected function writeProgress(string $progress) : void
     {
         $this->numTestsRun++;
 
@@ -126,7 +126,7 @@ public function endTest(Test $test, float $time) : void
      *
      * We'll handle the coloring ourselves.
      */
-    protected function writeProgressWithColor($color, $buffer) : void
+    protected function writeProgressWithColor(string $color, string $buffer) : void
     {
         $this->writeProgress($buffer);
     }