diff --git a/.php_cs b/.php_cs
index 3b63a310..981148fc 100644
--- a/.php_cs
+++ b/.php_cs
@@ -11,7 +11,7 @@ the LICENSE file that was distributed with this source code.
 @see https://github.com/localheinz/json-normalizer
 EOF;
 
-$config = Config\Factory::fromRuleSet(new Config\RuleSet\Php70($header), [
+$config = Config\Factory::fromRuleSet(new Config\RuleSet\Php71($header), [
     'mb_str_functions' => false,
 ]);
 
diff --git a/.travis.yml b/.travis.yml
index a6e29a03..31b5bd92 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,7 +19,7 @@ jobs:
   include:
     - stage: Style
 
-      php: 7.0
+      php: 7.1
 
       before_install:
         - source .travis/xdebug.sh
@@ -40,7 +40,7 @@ jobs:
 
       stage: Test
 
-      php: 7.0
+      php: 7.1
 
       env: WITH_LOWEST=true
 
@@ -63,24 +63,6 @@ jobs:
       after_success:
         - if [[ "$WITH_COVERAGE" == "true" ]]; then bash <(curl -s https://codecov.io/bash); fi
 
-    - <<: *TEST
-
-      php: 7.0
-
-      env: WITH_LOCKED=true
-
-    - <<: *TEST
-
-      php: 7.0
-
-      env: WITH_HIGHEST=true
-
-    - <<: *TEST
-
-      php: 7.1
-
-      env: WITH_LOWEST=true
-
     - <<: *TEST
 
       php: 7.1
diff --git a/composer.json b/composer.json
index b45beaec..89fd5857 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,7 @@
     }
   ],
   "require": {
-    "php": "^7.0",
+    "php": "^7.1",
     "justinrainbow/json-schema": "^4.0.0 || ^5.0.0",
     "localheinz/json-printer": "^1.0.0"
   },
diff --git a/composer.lock b/composer.lock
index c41df9c3..2e3c47a1 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "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": "4b97b1368210cf73f4f1a1abe9208898",
+    "content-hash": "7056ef9d643e1a3512de88286980c8fa",
     "packages": [
         {
             "name": "justinrainbow/json-schema",
@@ -3652,7 +3652,7 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "^7.0"
+        "php": "^7.1"
     },
     "platform-dev": []
 }
diff --git a/test/Bench/SchemaNormalizerBench.php b/test/Bench/SchemaNormalizerBench.php
index 1e15c4c0..36aad879 100644
--- a/test/Bench/SchemaNormalizerBench.php
+++ b/test/Bench/SchemaNormalizerBench.php
@@ -23,7 +23,7 @@ final class SchemaNormalizerBench
      * @Revs(5)
      * @Iterations(1)
      */
-    public function benchNormalizeProjectComposerFile()
+    public function benchNormalizeProjectComposerFile(): void
     {
         $this->normalize(
             __DIR__ . '/../../composer.json',
@@ -37,7 +37,7 @@ public function benchNormalizeProjectComposerFile()
      * @Revs(5)
      * @Iterations(1)
      */
-    public function benchNormalizeLargeComposerFile()
+    public function benchNormalizeLargeComposerFile(): void
     {
         $this->normalize(
             __DIR__ . '/../Fixture/LargeComposerFile/composer.json',
@@ -45,7 +45,7 @@ public function benchNormalizeLargeComposerFile()
         );
     }
 
-    private function normalize(string $file, string $schemaUri)
+    private function normalize(string $file, string $schemaUri): void
     {
         $original = \file_get_contents($file);
 
diff --git a/test/Unit/AbstractNormalizerTestCase.php b/test/Unit/AbstractNormalizerTestCase.php
index daa2f0fa..00eb3058 100644
--- a/test/Unit/AbstractNormalizerTestCase.php
+++ b/test/Unit/AbstractNormalizerTestCase.php
@@ -21,12 +21,12 @@ abstract class AbstractNormalizerTestCase extends Framework\TestCase
 {
     use Helper;
 
-    final public function testImplementsNormalizerInterface()
+    final public function testImplementsNormalizerInterface(): void
     {
         $this->assertClassImplementsInterface(NormalizerInterface::class, $this->className());
     }
 
-    final public function testNormalizeRejectsInvalidJson()
+    final public function testNormalizeRejectsInvalidJson(): void
     {
         $json = $this->faker()->realText();
 
diff --git a/test/Unit/AutoFormatNormalizerTest.php b/test/Unit/AutoFormatNormalizerTest.php
index b95e42d2..782ae604 100644
--- a/test/Unit/AutoFormatNormalizerTest.php
+++ b/test/Unit/AutoFormatNormalizerTest.php
@@ -27,7 +27,7 @@ final class AutoFormatNormalizerTest extends AbstractNormalizerTestCase
      * @param bool   $hasFinalNewLine
      * @param string $suffix
      */
-    public function testNormalizeEncodesWithJsonEncodeOptionsIndentsAndPossiblySuffixesWithFinalNewLine(bool $hasFinalNewLine, string $suffix)
+    public function testNormalizeEncodesWithJsonEncodeOptionsIndentsAndPossiblySuffixesWithFinalNewLine(bool $hasFinalNewLine, string $suffix): void
     {
         $faker = $this->faker();
 
@@ -123,7 +123,7 @@ public function providerFinalNewLine(): \Generator
             ],
         ];
 
-        foreach ($values as $key => list($hasFinalNewLine, $suffix)) {
+        foreach ($values as $key => [$hasFinalNewLine, $suffix]) {
             yield $key => [
                 $hasFinalNewLine,
                 $suffix,
diff --git a/test/Unit/CallableNormalizerTest.php b/test/Unit/CallableNormalizerTest.php
index 5d835036..abb62a1d 100644
--- a/test/Unit/CallableNormalizerTest.php
+++ b/test/Unit/CallableNormalizerTest.php
@@ -22,7 +22,7 @@ final class CallableNormalizerTest extends AbstractNormalizerTestCase
      *
      * @param callable $callable
      */
-    public function testNormalizePassesJsonThroughCallable(callable $callable)
+    public function testNormalizePassesJsonThroughCallable(callable $callable): void
     {
         $json = <<<'JSON'
 {
diff --git a/test/Unit/ChainNormalizerTest.php b/test/Unit/ChainNormalizerTest.php
index 39448d2e..656073da 100644
--- a/test/Unit/ChainNormalizerTest.php
+++ b/test/Unit/ChainNormalizerTest.php
@@ -19,7 +19,7 @@
 
 final class ChainNormalizerTest extends AbstractNormalizerTestCase
 {
-    public function testNormalizePassesJsonThroughNormalizers()
+    public function testNormalizePassesJsonThroughNormalizers(): void
     {
         $count = $this->faker()->numberBetween(3, 5);
 
diff --git a/test/Unit/FinalNewLineNormalizerTest.php b/test/Unit/FinalNewLineNormalizerTest.php
index 6a2dbdf8..4aa14ccb 100644
--- a/test/Unit/FinalNewLineNormalizerTest.php
+++ b/test/Unit/FinalNewLineNormalizerTest.php
@@ -22,7 +22,7 @@ final class FinalNewLineNormalizerTest extends AbstractNormalizerTestCase
      *
      * @param string $whitespace
      */
-    public function testNormalizeEnsuresSingleFinalNewLine(string $whitespace)
+    public function testNormalizeEnsuresSingleFinalNewLine(string $whitespace): void
     {
         $json = <<<'JSON'
 {
diff --git a/test/Unit/FixedFormatNormalizerTest.php b/test/Unit/FixedFormatNormalizerTest.php
index 0f7898b6..14d5d319 100644
--- a/test/Unit/FixedFormatNormalizerTest.php
+++ b/test/Unit/FixedFormatNormalizerTest.php
@@ -27,7 +27,7 @@ final class FixedFormatNormalizerTest extends AbstractNormalizerTestCase
      * @param bool   $hasFinalNewLine
      * @param string $suffix
      */
-    public function testNormalizeEncodesWithJsonEncodeOptionsIndentsAndPossiblySuffixesWithFinalNewLine(bool $hasFinalNewLine, string $suffix)
+    public function testNormalizeEncodesWithJsonEncodeOptionsIndentsAndPossiblySuffixesWithFinalNewLine(bool $hasFinalNewLine, string $suffix): void
     {
         $faker = $this->faker();
 
@@ -116,7 +116,7 @@ public function providerFinalNewLine(): \Generator
             ],
         ];
 
-        foreach ($values as $key => list($hasFinalNewLine, $suffix)) {
+        foreach ($values as $key => [$hasFinalNewLine, $suffix]) {
             yield $key => [
                 $hasFinalNewLine,
                 $suffix,
diff --git a/test/Unit/Format/FormatSnifferTest.php b/test/Unit/Format/FormatSnifferTest.php
index 664d7812..0c59d461 100644
--- a/test/Unit/Format/FormatSnifferTest.php
+++ b/test/Unit/Format/FormatSnifferTest.php
@@ -23,12 +23,12 @@ final class FormatSnifferTest extends Framework\TestCase
 {
     use Helper;
 
-    public function testImplementsSnifferInterface()
+    public function testImplementsSnifferInterface(): void
     {
         $this->assertClassImplementsInterface(FormatSnifferInterface::class, FormatSniffer::class);
     }
 
-    public function testSniffRejectsInvalidJson()
+    public function testSniffRejectsInvalidJson(): void
     {
         $json = $this->faker()->realText();
 
@@ -49,7 +49,7 @@ public function testSniffRejectsInvalidJson()
      * @param int    $jsonEncodeOptions
      * @param string $json
      */
-    public function testSniffReturnsFormatWithJsonEncodeOptions(int $jsonEncodeOptions, string $json)
+    public function testSniffReturnsFormatWithJsonEncodeOptions(int $jsonEncodeOptions, string $json): void
     {
         $sniffer = new FormatSniffer();
 
@@ -98,7 +98,7 @@ public function providerJsonAndJsonEncodeOptions(): array
      *
      * @param string $json
      */
-    public function testSniffReturnsFormatWithDefaultIndentIfUnableToSniff(string $json)
+    public function testSniffReturnsFormatWithDefaultIndentIfUnableToSniff(string $json): void
     {
         $sniffer = new FormatSniffer();
 
@@ -129,7 +129,7 @@ public function providerJsonWithoutWhitespace(): \Generator
      *
      * @param string $indent
      */
-    public function testSniffReturnsFormatWithIndentSniffedFromArray(string $indent)
+    public function testSniffReturnsFormatWithIndentSniffedFromArray(string $indent): void
     {
         $json = <<<JSON
 [
@@ -154,7 +154,7 @@ public function testSniffReturnsFormatWithIndentSniffedFromArray(string $indent)
      *
      * @param string $indent
      */
-    public function testSniffReturnsFormatWithIndentIndentSniffedFromObject(string $indent)
+    public function testSniffReturnsFormatWithIndentIndentSniffedFromObject(string $indent): void
     {
         $json = <<<JSON
 {
@@ -199,7 +199,7 @@ public function providerIndent(): \Generator
      *
      * @param string $actualWhitespace
      */
-    public function testSniffReturnsFormatWithoutFinalNewLineIfThereIsNoFinalNewLine(string $actualWhitespace)
+    public function testSniffReturnsFormatWithoutFinalNewLineIfThereIsNoFinalNewLine(string $actualWhitespace): void
     {
         $json = <<<'JSON'
 {
@@ -243,7 +243,7 @@ public function providerWhitespaceWithoutNewLine(): \Generator
      *
      * @param string $actualWhitespace
      */
-    public function testSniffReturnsFormatWithFinalNewLineIfThereIsAtLeastOneFinalNewLine(string $actualWhitespace)
+    public function testSniffReturnsFormatWithFinalNewLineIfThereIsAtLeastOneFinalNewLine(string $actualWhitespace): void
     {
         $json = <<<'JSON'
 {
diff --git a/test/Unit/Format/FormatTest.php b/test/Unit/Format/FormatTest.php
index dfd34288..a5f18a86 100644
--- a/test/Unit/Format/FormatTest.php
+++ b/test/Unit/Format/FormatTest.php
@@ -22,12 +22,12 @@ final class FormatTest extends Framework\TestCase
 {
     use Helper;
 
-    public function testImplementsFormatInterface()
+    public function testImplementsFormatInterface(): void
     {
         $this->assertClassImplementsInterface(FormatInterface::class, Format::class);
     }
 
-    public function testConstructorRejectsInvalidEncodeOptions()
+    public function testConstructorRejectsInvalidEncodeOptions(): void
     {
         $jsonEncodeOptions = -1;
         $indent = '  ';
@@ -51,7 +51,7 @@ public function testConstructorRejectsInvalidEncodeOptions()
      *
      * @param string $indent
      */
-    public function testConstructorRejectsInvalidIndent(string $indent)
+    public function testConstructorRejectsInvalidIndent(string $indent): void
     {
         $jsonEncodeOptions = 0;
         $hasFinalNewLine = true;
@@ -89,7 +89,7 @@ public function providerInvalidIndent(): \Generator
      * @param string $indent
      * @param bool   $hasFinalNewLine
      */
-    public function testConstructorSetsValues(string $indent, bool $hasFinalNewLine)
+    public function testConstructorSetsValues(string $indent, bool $hasFinalNewLine): void
     {
         $jsonEncodeOptions = JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES;
 
diff --git a/test/Unit/IndentNormalizerTest.php b/test/Unit/IndentNormalizerTest.php
index b203b730..4f3151ce 100644
--- a/test/Unit/IndentNormalizerTest.php
+++ b/test/Unit/IndentNormalizerTest.php
@@ -24,7 +24,7 @@ final class IndentNormalizerTest extends AbstractNormalizerTestCase
      *
      * @param string $indent
      */
-    public function testConstructorRejectsInvalidIndent(string $indent)
+    public function testConstructorRejectsInvalidIndent(string $indent): void
     {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage(\sprintf(
@@ -52,7 +52,7 @@ public function providerInvalidIndent(): \Generator
         }
     }
 
-    public function testNormalizeUsesPrinterToNormalizeJsonWithIndent()
+    public function testNormalizeUsesPrinterToNormalizeJsonWithIndent(): void
     {
         $indent = '  ';
 
diff --git a/test/Unit/JsonEncodeNormalizerTest.php b/test/Unit/JsonEncodeNormalizerTest.php
index 90b0dec1..73ac1e58 100644
--- a/test/Unit/JsonEncodeNormalizerTest.php
+++ b/test/Unit/JsonEncodeNormalizerTest.php
@@ -17,7 +17,7 @@
 
 final class JsonEncodeNormalizerTest extends AbstractNormalizerTestCase
 {
-    public function testConstructorRejectsInvalidJsonEncodeOptions()
+    public function testConstructorRejectsInvalidJsonEncodeOptions(): void
     {
         $jsonEncodeOptions = -1;
 
@@ -35,7 +35,7 @@ public function testConstructorRejectsInvalidJsonEncodeOptions()
      *
      * @param int $jsonEncodeOptions
      */
-    public function testNormalizeDecodesAndEncodesJsonWithJsonEncodeOptions(int $jsonEncodeOptions)
+    public function testNormalizeDecodesAndEncodesJsonWithJsonEncodeOptions(int $jsonEncodeOptions): void
     {
         $json = <<<'JSON'
 {
diff --git a/test/Unit/NoFinalNewLineNormalizerTest.php b/test/Unit/NoFinalNewLineNormalizerTest.php
index 24844ab0..c9ceb0ec 100644
--- a/test/Unit/NoFinalNewLineNormalizerTest.php
+++ b/test/Unit/NoFinalNewLineNormalizerTest.php
@@ -22,7 +22,7 @@ final class NoFinalNewLineNormalizerTest extends AbstractNormalizerTestCase
      *
      * @param string $whitespace
      */
-    public function testNormalizeRemovesAllWhitespaceFromEndOfJson(string $whitespace)
+    public function testNormalizeRemovesAllWhitespaceFromEndOfJson(string $whitespace): void
     {
         $json = <<<'JSON'
 {
diff --git a/test/Unit/ProjectCodeTest.php b/test/Unit/ProjectCodeTest.php
index 427f4df9..202b64cf 100644
--- a/test/Unit/ProjectCodeTest.php
+++ b/test/Unit/ProjectCodeTest.php
@@ -20,12 +20,12 @@ final class ProjectCodeTest extends Framework\TestCase
 {
     use Helper;
 
-    public function testProductionClassesAreAbstractOrFinal()
+    public function testProductionClassesAreAbstractOrFinal(): void
     {
         $this->assertClassesAreAbstractOrFinal(__DIR__ . '/../../src');
     }
 
-    public function testProductionClassesHaveTests()
+    public function testProductionClassesHaveTests(): void
     {
         $this->assertClassesHaveTests(
             __DIR__ . '/../../src',
@@ -34,7 +34,7 @@ public function testProductionClassesHaveTests()
         );
     }
 
-    public function testTestClassesAreAbstractOrFinal()
+    public function testTestClassesAreAbstractOrFinal(): void
     {
         $this->assertClassesAreAbstractOrFinal(__DIR__ . '/..');
     }
diff --git a/test/Unit/SchemaNormalizerTest.php b/test/Unit/SchemaNormalizerTest.php
index 83594be9..c78d09ef 100644
--- a/test/Unit/SchemaNormalizerTest.php
+++ b/test/Unit/SchemaNormalizerTest.php
@@ -21,7 +21,7 @@
 
 final class SchemaNormalizerTest extends AbstractNormalizerTestCase
 {
-    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriCouldNotBeResolved()
+    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriCouldNotBeResolved(): void
     {
         $json = <<<'JSON'
 {
@@ -54,7 +54,7 @@ public function testNormalizeThrowsRuntimeExceptionIfSchemaUriCouldNotBeResolved
         $normalizer->normalize($json);
     }
 
-    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesUnreadableResource()
+    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesUnreadableResource(): void
     {
         $json = <<<'JSON'
 {
@@ -87,7 +87,7 @@ public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesUnreadab
         $normalizer->normalize($json);
     }
 
-    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesResourceWithInvalidMediaType()
+    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesResourceWithInvalidMediaType(): void
     {
         $json = <<<'JSON'
 {
@@ -120,7 +120,7 @@ public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesResource
         $normalizer->normalize($json);
     }
 
-    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesResourceWithInvalidJson()
+    public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesResourceWithInvalidJson(): void
     {
         $json = <<<'JSON'
 {
@@ -153,7 +153,7 @@ public function testNormalizeThrowsRuntimeExceptionIfSchemaUriReferencesResource
         $normalizer->normalize($json);
     }
 
-    public function testNormalizeRejectsInvalidJsonAccordingToSchema()
+    public function testNormalizeRejectsInvalidJsonAccordingToSchema(): void
     {
         $json = <<<'JSON'
 {
@@ -205,7 +205,7 @@ public function testNormalizeRejectsInvalidJsonAccordingToSchema()
         $normalizer->normalize($json);
     }
 
-    public function testNormalizeThrowsRuntimeExceptionIfNormalizedIsInvalidAccordingToSchema()
+    public function testNormalizeThrowsRuntimeExceptionIfNormalizedIsInvalidAccordingToSchema(): void
     {
         $json = <<<'JSON'
 {
@@ -291,7 +291,7 @@ public function testNormalizeThrowsRuntimeExceptionIfNormalizedIsInvalidAccordin
      * @param string $json
      * @param string $schemaUri
      */
-    public function testNormalizeNormalizes(string $expected, string $json, string $schemaUri)
+    public function testNormalizeNormalizes(string $expected, string $json, string $schemaUri): void
     {
         $normalizer = new SchemaNormalizer($schemaUri);
 
diff --git a/test/Unit/Validator/SchemaValidatorTest.php b/test/Unit/Validator/SchemaValidatorTest.php
index 32cab4f8..36c68aae 100644
--- a/test/Unit/Validator/SchemaValidatorTest.php
+++ b/test/Unit/Validator/SchemaValidatorTest.php
@@ -24,7 +24,7 @@ final class SchemaValidatorTest extends Framework\TestCase
 {
     use Helper;
 
-    public function testImplementsSchemaValidatorInterface()
+    public function testImplementsSchemaValidatorInterface(): void
     {
         $this->assertClassImplementsInterface(SchemaValidatorInterface::class, SchemaValidator::class);
     }
@@ -34,7 +34,7 @@ public function testImplementsSchemaValidatorInterface()
      *
      * @param bool $isValid
      */
-    public function testValidateUsesSchemaValidator(bool $isValid)
+    public function testValidateUsesSchemaValidator(bool $isValid): void
     {
         $dataJson = <<<'JSON'
 {