diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 83dc88da..71150aa4 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: [ "7.1", "7.2", "7.3", "7.4", "8.0", "8.1"]
+        php: [ "7.4", "8.0", "8.1"]
     name: PHP ${{matrix.php }} Unit Test
     steps:
       - uses: actions/checkout@v2
diff --git a/composer.json b/composer.json
index 2a3cb2df..5551d316 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
     ],
     "license": "BSD-3-Clause",
     "require": {
-        "php": "^7.1||^8.0"
+        "php": "^7.4||^8.0"
     },
     "suggest": {
         "paragonie/sodium_compat": "Support EdDSA (Ed25519) signatures when libsodium is not present"
@@ -31,9 +31,9 @@
         }
     },
     "require-dev": {
-        "guzzlehttp/guzzle": "^6.5||^7.4",
-        "phpspec/prophecy-phpunit": "^1.1",
-        "phpunit/phpunit": "^7.5||^9.5",
+        "guzzlehttp/guzzle": "^7.4",
+        "phpspec/prophecy-phpunit": "^2.0",
+        "phpunit/phpunit": "^9.5",
         "psr/cache": "^1.0||^2.0",
         "psr/http-client": "^1.0",
         "psr/http-factory": "^1.0"
diff --git a/src/CachedKeySet.php b/src/CachedKeySet.php
index 87f470d7..cf833ba4 100644
--- a/src/CachedKeySet.php
+++ b/src/CachedKeySet.php
@@ -16,62 +16,33 @@
  */
 class CachedKeySet implements ArrayAccess
 {
-    /**
-     * @var string
-     */
-    private $jwksUri;
-    /**
-     * @var ClientInterface
-     */
-    private $httpClient;
-    /**
-     * @var RequestFactoryInterface
-     */
-    private $httpFactory;
-    /**
-     * @var CacheItemPoolInterface
-     */
-    private $cache;
-    /**
-     * @var ?int
-     */
-    private $expiresAfter;
-    /**
-     * @var ?CacheItemInterface
-     */
-    private $cacheItem;
-    /**
-     * @var array<string, Key>
-     */
-    private $keySet;
-    /**
-     * @var string
-     */
-    private $cacheKey;
-    /**
-     * @var string
-     */
-    private $cacheKeyPrefix = 'jwks';
-    /**
-     * @var int
-     */
-    private $maxKeyLength = 64;
-    /**
-     * @var bool
-     */
-    private $rateLimit;
-    /**
-     * @var string
-     */
-    private $rateLimitCacheKey;
-    /**
-     * @var int
-     */
-    private $maxCallsPerMinute = 10;
-    /**
-     * @var string|null
-     */
-    private $defaultAlg;
+    private string $jwksUri;
+
+    private ClientInterface $httpClient;
+
+    private RequestFactoryInterface $httpFactory;
+
+    private CacheItemPoolInterface $cache;
+
+    private ?int $expiresAfter;
+
+    private ?CacheItemInterface $cacheItem = null;
+
+    private ?array $keySet = null;
+
+    private string $cacheKey;
+
+    private string $cacheKeyPrefix = 'jwks';
+
+    private int $maxKeyLength = 64;
+
+    private bool $rateLimit;
+
+    private string $rateLimitCacheKey;
+
+    private int $maxCallsPerMinute = 10;
+
+    private ?string $defaultAlg;
 
     public function __construct(
         string $jwksUri,
diff --git a/src/JWK.php b/src/JWK.php
index 15631ecc..8ddd28c7 100644
--- a/src/JWK.php
+++ b/src/JWK.php
@@ -34,7 +34,7 @@ class JWK
      * Parse a set of JWK keys
      *
      * @param array<mixed> $jwks The JSON Web Key Set as an associative array
-     * @param string       $defaultAlg The algorithm for the Key object if "alg" is not set in the
+     * @param string|null  $defaultAlg The algorithm for the Key object if "alg" is not set in the
      *                                 JSON Web Key Set
      *
      * @return array<string, Key> An associative array of key IDs (kid) to Key objects
@@ -75,7 +75,7 @@ public static function parseKeySet(array $jwks, string $defaultAlg = null): arra
      * Parse a JWK key
      *
      * @param array<mixed> $jwk An individual JWK
-     * @param string       $defaultAlg The algorithm for the Key object if "alg" is not set in the
+     * @param string|null  $defaultAlg The algorithm for the Key object if "alg" is not set in the
      *                                 JSON Web Key Set
      *
      * @return Key The key object for the JWK
diff --git a/src/JWT.php b/src/JWT.php
index 977d7fbd..821eea22 100644
--- a/src/JWT.php
+++ b/src/JWT.php
@@ -35,24 +35,20 @@ class JWT
      * When checking nbf, iat or expiration times,
      * we want to provide some extra leeway time to
      * account for clock skew.
-     *
-     * @var int
      */
-    public static $leeway = 0;
+    public static int $leeway = 0;
 
     /**
      * Allow the current timestamp to be specified.
      * Useful for fixing a value within unit testing.
      * Will default to PHP time() value if null.
-     *
-     * @var ?int
      */
-    public static $timestamp = null;
+    public static ?int $timestamp = null;
 
     /**
      * @var array<string, string[]>
      */
-    public static $supported_algs = [
+    public static array $supported_algs = [
         'ES384' => ['openssl', 'SHA384'],
         'ES256' => ['openssl', 'SHA256'],
         'HS256' => ['hash_hmac', 'SHA256'],
@@ -172,7 +168,7 @@ public static function decode(
      * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate $key The secret key.
      * @param string                $alg     Supported algorithms are 'ES384','ES256', 'HS256', 'HS384',
      *                                       'HS512', 'RS256', 'RS384', and 'RS512'
-     * @param string                $keyId
+     * @param string|null           $keyId
      * @param array<string, string> $head    An array with header elements to attach
      *
      * @return string A signed JWT
@@ -480,9 +476,7 @@ private static function handleJsonError(int $errno): void
             JSON_ERROR_UTF8 => 'Malformed UTF-8 characters' //PHP >= 5.3.3
         ];
         throw new DomainException(
-            isset($messages[$errno])
-            ? $messages[$errno]
-            : 'Unknown JSON error: ' . $errno
+            $messages[$errno] ?? 'Unknown JSON error: ' . $errno
         );
     }
 
diff --git a/src/Key.php b/src/Key.php
index 00cf7f2e..42a12ee6 100644
--- a/src/Key.php
+++ b/src/Key.php
@@ -12,7 +12,7 @@ class Key
     /** @var string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate */
     private $keyMaterial;
     /** @var string */
-    private $algorithm;
+    private string $algorithm;
 
     /**
      * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate $keyMaterial
diff --git a/tests/CachedKeySetTest.php b/tests/CachedKeySetTest.php
index 73b1213d..9eced110 100644
--- a/tests/CachedKeySetTest.php
+++ b/tests/CachedKeySetTest.php
@@ -6,6 +6,7 @@
 use OutOfBoundsException;
 use PHPUnit\Framework\TestCase;
 use Prophecy\Argument;
+use Prophecy\PhpUnit\ProphecyTrait;
 use Psr\Cache\CacheItemInterface;
 use Psr\Cache\CacheItemPoolInterface;
 use Psr\Http\Client\ClientInterface;
@@ -14,16 +15,18 @@
 
 class CachedKeySetTest extends TestCase
 {
-    private $testJwksUri = 'https://jwk.uri';
-    private $testJwksUriKey = 'jwkshttpsjwk.uri';
-    private $testJwks1 = '{"keys": [{"kid":"foo","kty":"RSA","alg":"foo","n":"","e":""}]}';
-    private $testJwks2 = '{"keys": [{"kid":"bar","kty":"RSA","alg":"bar","n":"","e":""}]}';
-    private $testJwks3 = '{"keys": [{"kid":"baz","kty":"RSA","n":"","e":""}]}';
+    use ProphecyTrait;
 
-    private $googleRsaUri = 'https://www.googleapis.com/oauth2/v3/certs';
+    private string $testJwksUri = 'https://jwk.uri';
+    private string $testJwksUriKey = 'jwkshttpsjwk.uri';
+    private string $testJwks1 = '{"keys": [{"kid":"foo","kty":"RSA","alg":"foo","n":"","e":""}]}';
+    private string $testJwks2 = '{"keys": [{"kid":"bar","kty":"RSA","alg":"bar","n":"","e":""}]}';
+    private string $testJwks3 = '{"keys": [{"kid":"baz","kty":"RSA","n":"","e":""}]}';
+
+    private string $googleRsaUri = 'https://www.googleapis.com/oauth2/v3/certs';
     // private $googleEcUri = 'https://www.gstatic.com/iap/verify/public_key-jwk';
 
-    public function testEmptyUriThrowsException()
+    public function testEmptyUriThrowsException(): void
     {
         $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage('JWKS URI is empty');
@@ -38,7 +41,7 @@ public function testEmptyUriThrowsException()
         $cachedKeySet['foo'];
     }
 
-    public function testOffsetSetThrowsException()
+    public function testOffsetSetThrowsException(): void
     {
         $this->expectException(LogicException::class);
         $this->expectExceptionMessage('Method not implemented');
@@ -53,7 +56,7 @@ public function testOffsetSetThrowsException()
         $cachedKeySet['foo'] = 'bar';
     }
 
-    public function testOffsetUnsetThrowsException()
+    public function testOffsetUnsetThrowsException(): void
     {
         $this->expectException(LogicException::class);
         $this->expectExceptionMessage('Method not implemented');
@@ -68,7 +71,7 @@ public function testOffsetUnsetThrowsException()
         unset($cachedKeySet['foo']);
     }
 
-    public function testOutOfBoundsThrowsException()
+    public function testOutOfBoundsThrowsException(): void
     {
         $this->expectException(OutOfBoundsException::class);
         $this->expectExceptionMessage('Key ID not found');
@@ -84,7 +87,7 @@ public function testOutOfBoundsThrowsException()
         $cachedKeySet['bar'];
     }
 
-    public function testWithExistingKeyId()
+    public function testWithExistingKeyId(): void
     {
         $cachedKeySet = new CachedKeySet(
             $this->testJwksUri,
@@ -96,7 +99,7 @@ public function testWithExistingKeyId()
         $this->assertEquals('foo', $cachedKeySet['foo']->getAlgorithm());
     }
 
-    public function testWithDefaultAlg()
+    public function testWithDefaultAlg(): void
     {
         $cachedKeySet = new CachedKeySet(
             $this->testJwksUri,
@@ -111,7 +114,7 @@ public function testWithDefaultAlg()
         $this->assertEquals('baz256', $cachedKeySet['baz']->getAlgorithm());
     }
 
-    public function testKeyIdIsCached()
+    public function testKeyIdIsCached(): void
     {
         $cacheItem = $this->prophesize(CacheItemInterface::class);
         $cacheItem->isHit()
@@ -135,7 +138,7 @@ public function testKeyIdIsCached()
         $this->assertEquals('foo', $cachedKeySet['foo']->getAlgorithm());
     }
 
-    public function testCachedKeyIdRefresh()
+    public function testCachedKeyIdRefresh(): void
     {
         $cacheItem = $this->prophesize(CacheItemInterface::class);
         $cacheItem->isHit()
@@ -171,7 +174,7 @@ public function testCachedKeyIdRefresh()
         $this->assertEquals('bar', $cachedKeySet['bar']->getAlgorithm());
     }
 
-    public function testCacheItemWithExpiresAfter()
+    public function testCacheItemWithExpiresAfter(): void
     {
         $expiresAfter = 10;
         $cacheItem = $this->prophesize(CacheItemInterface::class);
@@ -207,7 +210,7 @@ public function testCacheItemWithExpiresAfter()
         $this->assertEquals('foo', $cachedKeySet['foo']->getAlgorithm());
     }
 
-    public function testJwtVerify()
+    public function testJwtVerify(): void
     {
         $privKey1 = file_get_contents(__DIR__ . '/data/rsa1-private.pem');
         $payload = ['sub' => 'foo', 'exp' => strtotime('+10 seconds')];
@@ -236,7 +239,7 @@ public function testJwtVerify()
         $this->assertEquals('foo', $result->sub);
     }
 
-    public function testRateLimit()
+    public function testRateLimit(): void
     {
         // We request the key 11 times, HTTP should only be called 10 times
         $shouldBeCalledTimes = 10;
@@ -293,7 +296,7 @@ public function testFullIntegration(string $jwkUri): void
         $this->assertEquals($keys['keys'][0]['alg'], $key->getAlgorithm());
     }
 
-    public function provideFullIntegration()
+    public function provideFullIntegration(): array
     {
         return [
             [$this->googleRsaUri],
@@ -301,7 +304,7 @@ public function provideFullIntegration()
         ];
     }
 
-    private function getMockHttpClient($testJwks, int $timesCalled = 1)
+    private function getMockHttpClient($testJwks, int $timesCalled = 1): object
     {
         $body = $this->prophesize('Psr\Http\Message\StreamInterface');
         $body->__toString()
@@ -321,7 +324,7 @@ private function getMockHttpClient($testJwks, int $timesCalled = 1)
         return $http->reveal();
     }
 
-    private function getMockHttpFactory(int $timesCalled = 1)
+    private function getMockHttpFactory(int $timesCalled = 1): object
     {
         $request = $this->prophesize('Psr\Http\Message\RequestInterface');
         $factory = $this->prophesize(RequestFactoryInterface::class);
@@ -332,7 +335,7 @@ private function getMockHttpFactory(int $timesCalled = 1)
         return $factory->reveal();
     }
 
-    private function getMockEmptyCache()
+    private function getMockEmptyCache(): object
     {
         $cacheItem = $this->prophesize(CacheItemInterface::class);
         $cacheItem->isHit()
diff --git a/tests/JWKTest.php b/tests/JWKTest.php
index b8c24f98..8691b7df 100644
--- a/tests/JWKTest.php
+++ b/tests/JWKTest.php
@@ -12,7 +12,7 @@ class JWKTest extends TestCase
     private static $privKey1;
     private static $privKey2;
 
-    public function testMissingKty()
+    public function testMissingKty(): void
     {
         $this->expectException(UnexpectedValueException::class);
         $this->expectExceptionMessage('JWK must contain a "kty" parameter');
@@ -21,7 +21,7 @@ public function testMissingKty()
         $keys = JWK::parseKeySet(['keys' => [$badJwk]]);
     }
 
-    public function testInvalidAlgorithm()
+    public function testInvalidAlgorithm(): void
     {
         $this->expectException(UnexpectedValueException::class);
         $this->expectExceptionMessage('No supported algorithms found in JWK Set');
@@ -30,7 +30,7 @@ public function testInvalidAlgorithm()
         $keys = JWK::parseKeySet(['keys' => [$badJwk]]);
     }
 
-    public function testParsePrivateKey()
+    public function testParsePrivateKey(): void
     {
         $this->expectException(UnexpectedValueException::class);
         $this->expectExceptionMessage('RSA private keys are not supported');
@@ -44,7 +44,7 @@ public function testParsePrivateKey()
         JWK::parseKeySet($jwkSet);
     }
 
-    public function testParsePrivateKeyWithoutAlg()
+    public function testParsePrivateKeyWithoutAlg(): void
     {
         $this->expectException(UnexpectedValueException::class);
         $this->expectExceptionMessage('JWK must contain an "alg" parameter');
@@ -58,7 +58,7 @@ public function testParsePrivateKeyWithoutAlg()
         JWK::parseKeySet($jwkSet);
     }
 
-    public function testParsePrivateKeyWithoutAlgWithDefaultAlgParameter()
+    public function testParsePrivateKeyWithoutAlgWithDefaultAlgParameter(): void
     {
         $jwkSet = json_decode(
             file_get_contents(__DIR__ . '/data/rsa-jwkset.json'),
@@ -70,7 +70,7 @@ public function testParsePrivateKeyWithoutAlgWithDefaultAlgParameter()
         $this->assertEquals('foo', $jwks['jwk1']->getAlgorithm());
     }
 
-    public function testParseKeyWithEmptyDValue()
+    public function testParseKeyWithEmptyDValue(): void
     {
         $jwkSet = json_decode(
             file_get_contents(__DIR__ . '/data/rsa-jwkset.json'),
@@ -84,7 +84,7 @@ public function testParseKeyWithEmptyDValue()
         $this->assertTrue(\is_array($keys));
     }
 
-    public function testParseJwkKeySet()
+    public function testParseJwkKeySet(): void
     {
         $jwkSet = json_decode(
             file_get_contents(__DIR__ . '/data/rsa-jwkset.json'),
@@ -96,7 +96,7 @@ public function testParseJwkKeySet()
         self::$keys = $keys;
     }
 
-    public function testParseJwkKey_empty()
+    public function testParseJwkKey_empty(): void
     {
         $this->expectException(InvalidArgumentException::class);
         $this->expectExceptionMessage('JWK must not be empty');
@@ -104,7 +104,7 @@ public function testParseJwkKey_empty()
         JWK::parseKeySet(['keys' => [[]]]);
     }
 
-    public function testParseJwkKeySet_empty()
+    public function testParseJwkKeySet_empty(): void
     {
         $this->expectException(InvalidArgumentException::class);
         $this->expectExceptionMessage('JWK Set did not contain any keys');
@@ -115,7 +115,7 @@ public function testParseJwkKeySet_empty()
     /**
      * @depends testParseJwkKeySet
      */
-    public function testDecodeByJwkKeySetTokenExpired()
+    public function testDecodeByJwkKeySetTokenExpired(): void
     {
         $privKey1 = file_get_contents(__DIR__ . '/data/rsa1-private.pem');
         $payload = ['exp' => strtotime('-1 hour')];
@@ -129,7 +129,7 @@ public function testDecodeByJwkKeySetTokenExpired()
     /**
      * @dataProvider provideDecodeByJwkKeySet
      */
-    public function testDecodeByJwkKeySet($pemFile, $jwkFile, $alg)
+    public function testDecodeByJwkKeySet($pemFile, $jwkFile, $alg): void
     {
         $privKey1 = file_get_contents(__DIR__ . '/data/' . $pemFile);
         $payload = ['sub' => 'foo', 'exp' => strtotime('+10 seconds')];
@@ -146,7 +146,7 @@ public function testDecodeByJwkKeySet($pemFile, $jwkFile, $alg)
         $this->assertEquals('foo', $result->sub);
     }
 
-    public function provideDecodeByJwkKeySet()
+    public function provideDecodeByJwkKeySet(): array
     {
         return [
             ['rsa1-private.pem', 'rsa-jwkset.json', 'RS256'],
@@ -157,7 +157,7 @@ public function provideDecodeByJwkKeySet()
     /**
      * @depends testParseJwkKeySet
      */
-    public function testDecodeByMultiJwkKeySet()
+    public function testDecodeByMultiJwkKeySet(): void
     {
         $privKey2 = file_get_contents(__DIR__ . '/data/rsa2-private.pem');
         $payload = ['sub' => 'bar', 'exp' => strtotime('+10 seconds')];
diff --git a/tests/JWTTest.php b/tests/JWTTest.php
index 58c334ed..040e73c2 100644
--- a/tests/JWTTest.php
+++ b/tests/JWTTest.php
@@ -12,7 +12,7 @@
 
 class JWTTest extends TestCase
 {
-    public function testUrlSafeCharacters()
+    public function testUrlSafeCharacters(): void
     {
         $encoded = JWT::encode(['message' => 'f?'], 'a', 'HS256');
         $expected = new stdClass();
@@ -20,19 +20,19 @@ public function testUrlSafeCharacters()
         $this->assertEquals($expected, JWT::decode($encoded, new Key('a', 'HS256')));
     }
 
-    public function testMalformedUtf8StringsFail()
+    public function testMalformedUtf8StringsFail(): void
     {
         $this->expectException(DomainException::class);
         JWT::encode(['message' => pack('c', 128)], 'a', 'HS256');
     }
 
-    public function testMalformedJsonThrowsException()
+    public function testMalformedJsonThrowsException(): void
     {
         $this->expectException(DomainException::class);
         JWT::jsonDecode('this is not valid JSON string');
     }
 
-    public function testExpiredToken()
+    public function testExpiredToken(): void
     {
         $this->expectException(ExpiredException::class);
         $payload = [
@@ -43,7 +43,7 @@ public function testExpiredToken()
         JWT::decode($encoded, new Key('my_key', 'HS256'));
     }
 
-    public function testBeforeValidTokenWithNbf()
+    public function testBeforeValidTokenWithNbf(): void
     {
         $this->expectException(BeforeValidException::class);
         $payload = [
@@ -54,7 +54,7 @@ public function testBeforeValidTokenWithNbf()
         JWT::decode($encoded, new Key('my_key', 'HS256'));
     }
 
-    public function testBeforeValidTokenWithIat()
+    public function testBeforeValidTokenWithIat(): void
     {
         $this->expectException(BeforeValidException::class);
         $payload = [
@@ -65,7 +65,7 @@ public function testBeforeValidTokenWithIat()
         JWT::decode($encoded, new Key('my_key', 'HS256'));
     }
 
-    public function testValidToken()
+    public function testValidToken(): void
     {
         $payload = [
             'message' => 'abc',
@@ -73,10 +73,10 @@ public function testValidToken()
         ];
         $encoded = JWT::encode($payload, 'my_key', 'HS256');
         $decoded = JWT::decode($encoded, new Key('my_key', 'HS256'));
-        $this->assertEquals($decoded->message, 'abc');
+        $this->assertEquals('abc', $decoded->message);
     }
 
-    public function testValidTokenWithLeeway()
+    public function testValidTokenWithLeeway(): void
     {
         JWT::$leeway = 60;
         $payload = [
@@ -85,11 +85,11 @@ public function testValidTokenWithLeeway()
         ];
         $encoded = JWT::encode($payload, 'my_key', 'HS256');
         $decoded = JWT::decode($encoded, new Key('my_key', 'HS256'));
-        $this->assertEquals($decoded->message, 'abc');
+        $this->assertEquals('abc', $decoded->message);
         JWT::$leeway = 0;
     }
 
-    public function testExpiredTokenWithLeeway()
+    public function testExpiredTokenWithLeeway(): void
     {
         JWT::$leeway = 60;
         $payload = [
@@ -99,11 +99,11 @@ public function testExpiredTokenWithLeeway()
         $this->expectException(ExpiredException::class);
         $encoded = JWT::encode($payload, 'my_key', 'HS256');
         $decoded = JWT::decode($encoded, new Key('my_key', 'HS256'));
-        $this->assertEquals($decoded->message, 'abc');
+        $this->assertEquals('abc', $decoded->message);
         JWT::$leeway = 0;
     }
 
-    public function testValidTokenWithNbf()
+    public function testValidTokenWithNbf(): void
     {
         $payload = [
             'message' => 'abc',
@@ -113,10 +113,10 @@ public function testValidTokenWithNbf()
         ];
         $encoded = JWT::encode($payload, 'my_key', 'HS256');
         $decoded = JWT::decode($encoded, new Key('my_key', 'HS256'));
-        $this->assertEquals($decoded->message, 'abc');
+        $this->assertEquals('abc', $decoded->message);
     }
 
-    public function testValidTokenWithNbfLeeway()
+    public function testValidTokenWithNbfLeeway(): void
     {
         JWT::$leeway = 60;
         $payload = [
@@ -125,11 +125,11 @@ public function testValidTokenWithNbfLeeway()
         ];
         $encoded = JWT::encode($payload, 'my_key', 'HS256');
         $decoded = JWT::decode($encoded, new Key('my_key', 'HS256'));
-        $this->assertEquals($decoded->message, 'abc');
+        $this->assertEquals('abc', $decoded->message);
         JWT::$leeway = 0;
     }
 
-    public function testInvalidTokenWithNbfLeeway()
+    public function testInvalidTokenWithNbfLeeway(): void
     {
         JWT::$leeway = 60;
         $payload = [
@@ -142,7 +142,7 @@ public function testInvalidTokenWithNbfLeeway()
         JWT::$leeway = 0;
     }
 
-    public function testValidTokenWithIatLeeway()
+    public function testValidTokenWithIatLeeway(): void
     {
         JWT::$leeway = 60;
         $payload = [
@@ -151,11 +151,11 @@ public function testValidTokenWithIatLeeway()
         ];
         $encoded = JWT::encode($payload, 'my_key', 'HS256');
         $decoded = JWT::decode($encoded, new Key('my_key', 'HS256'));
-        $this->assertEquals($decoded->message, 'abc');
+        $this->assertEquals('abc', $decoded->message);
         JWT::$leeway = 0;
     }
 
-    public function testInvalidTokenWithIatLeeway()
+    public function testInvalidTokenWithIatLeeway(): void
     {
         JWT::$leeway = 60;
         $payload = [
@@ -168,7 +168,7 @@ public function testInvalidTokenWithIatLeeway()
         JWT::$leeway = 0;
     }
 
-    public function testInvalidToken()
+    public function testInvalidToken(): void
     {
         $payload = [
             'message' => 'abc',
@@ -179,7 +179,7 @@ public function testInvalidToken()
         JWT::decode($encoded, new Key('my_key2', 'HS256'));
     }
 
-    public function testNullKeyFails()
+    public function testNullKeyFails(): void
     {
         $payload = [
             'message' => 'abc',
@@ -190,7 +190,7 @@ public function testNullKeyFails()
         JWT::decode($encoded, new Key(null, 'HS256'));
     }
 
-    public function testEmptyKeyFails()
+    public function testEmptyKeyFails(): void
     {
         $payload = [
             'message' => 'abc',
@@ -201,7 +201,7 @@ public function testEmptyKeyFails()
         JWT::decode($encoded, new Key('', 'HS256'));
     }
 
-    public function testKIDChooser()
+    public function testKIDChooser(): void
     {
         $keys = [
             '1' => new Key('my_key', 'HS256'),
@@ -214,7 +214,7 @@ public function testKIDChooser()
         $this->assertEquals($decoded, $expected);
     }
 
-    public function testArrayAccessKIDChooser()
+    public function testArrayAccessKIDChooser(): void
     {
         $keys = new ArrayObject([
             '1' => new Key('my_key', 'HS256'),
@@ -227,28 +227,28 @@ public function testArrayAccessKIDChooser()
         $this->assertEquals($decoded, $expected);
     }
 
-    public function testNoneAlgorithm()
+    public function testNoneAlgorithm(): void
     {
         $msg = JWT::encode(['message' => 'abc'], 'my_key', 'HS256');
         $this->expectException(UnexpectedValueException::class);
         JWT::decode($msg, new Key('my_key', 'none'));
     }
 
-    public function testIncorrectAlgorithm()
+    public function testIncorrectAlgorithm(): void
     {
         $msg = JWT::encode(['message' => 'abc'], 'my_key', 'HS256');
         $this->expectException(UnexpectedValueException::class);
         JWT::decode($msg, new Key('my_key', 'RS256'));
     }
 
-    public function testEmptyAlgorithm()
+    public function testEmptyAlgorithm(): void
     {
         $msg = JWT::encode(['message' => 'abc'], 'my_key', 'HS256');
         $this->expectException(InvalidArgumentException::class);
         JWT::decode($msg, new Key('my_key', ''));
     }
 
-    public function testAdditionalHeaders()
+    public function testAdditionalHeaders(): void
     {
         $msg = JWT::encode(['message' => 'abc'], 'my_key', 'HS256', null, ['cty' => 'test-eit;v=1']);
         $expected = new stdClass();
@@ -256,20 +256,20 @@ public function testAdditionalHeaders()
         $this->assertEquals(JWT::decode($msg, new Key('my_key', 'HS256')), $expected);
     }
 
-    public function testInvalidSegmentCount()
+    public function testInvalidSegmentCount(): void
     {
         $this->expectException(UnexpectedValueException::class);
         JWT::decode('brokenheader.brokenbody', new Key('my_key', 'HS256'));
     }
 
-    public function testInvalidSignatureEncoding()
+    public function testInvalidSignatureEncoding(): void
     {
         $msg = 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6MSwibmFtZSI6ImZvbyJ9.Q4Kee9E8o0Xfo4ADXvYA8t7dN_X_bU9K5w6tXuiSjlUxx';
         $this->expectException(UnexpectedValueException::class);
         JWT::decode($msg, new Key('secret', 'HS256'));
     }
 
-    public function testHSEncodeDecode()
+    public function testHSEncodeDecode(): void
     {
         $msg = JWT::encode(['message' => 'abc'], 'my_key', 'HS256');
         $expected = new stdClass();
@@ -277,7 +277,7 @@ public function testHSEncodeDecode()
         $this->assertEquals(JWT::decode($msg, new Key('my_key', 'HS256')), $expected);
     }
 
-    public function testRSEncodeDecode()
+    public function testRSEncodeDecode(): void
     {
         $privKey = openssl_pkey_new(['digest_alg' => 'sha256',
             'private_key_bits' => 1024,