diff --git a/.github/apply-phpunit-patches.sh b/.github/apply-phpunit-patches.sh
deleted file mode 100644
index 4761b3e8d..000000000
--- a/.github/apply-phpunit-patches.sh
+++ /dev/null
@@ -1,18 +0,0 @@
-#!/bin/sh
-
-# Script used from php-webdriver/php-webdriver
-
-# All commands below must not fail
-set -e
-
-# Be in the root dir
-cd "$(dirname "$0")/../"
-
-find tests/ -type f -print0 | xargs -0 sed -i 's/function setUp(): void/function setUp()/g';
-find tests/ -type f -print0 | xargs -0 sed -i 's/function tearDown(): void/function tearDown()/g';
-
-# Drop the listener from the config file
-sed -i '/<listeners>/,+2d' phpunit.xml.dist;
-
-# Return back to original dir
-cd - > /dev/null
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 35e4cdb84..efa68af5c 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -9,7 +9,7 @@ jobs:
         runs-on: ubuntu-latest
         strategy:
             matrix:
-                php: [ "5.6", "7.0", "7.1", "7.2", "7.3", "7.4", "8.0", "8.1" ]
+                php: [ "7.1", "7.2", "7.3", "7.4", "8.0", "8.1" ]
         name: PHP ${{matrix.php }} Unit Test
         steps:
             - uses: actions/checkout@v3
@@ -23,46 +23,34 @@ jobs:
                 timeout_minutes: 10
                 max_attempts: 3
                 command: composer install
-            - if: ${{ contains(fromJson('["5.6", "7.0", "7.1"]'), matrix.php)}}
-              name: Run PHPUnit Patches
-              run: sh .github/apply-phpunit-patches.sh
             - name: Run Script
               run: vendor/bin/phpunit
     test_lowest:
         runs-on: ubuntu-latest
-        strategy:
-            matrix:
-                php: [ "5.6", "7.2" ]
-        name: PHP ${{matrix.php }} Unit Test Prefer Lowest
+        name: Test Prefer Lowest
         steps:
             - uses: actions/checkout@v3
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
               with:
-                php-version: ${{ matrix.php }}
+                php-version: "7.1"
             - name: Install Dependencies
               uses: nick-invision/retry@v2
               with:
                 timeout_minutes: 10
                 max_attempts: 3
                 command: composer update --prefer-lowest
-            - if: ${{ matrix.php == '5.6' }}
-              name: Run PHPUnit Patches
-              run: sh .github/apply-phpunit-patches.sh
             - name: Run Script
               run: vendor/bin/phpunit
     guzzle6:
         runs-on: ubuntu-latest
-        strategy:
-            matrix:
-                php: [ "7.2" ]
-        name: PHP ${{ matrix.php }} Unit Test Guzzle 6
+        name: Test Guzzle 6
         steps:
             - uses: actions/checkout@v3
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
               with:
-                php-version: ${{ matrix.php }}
+                php-version: "7.2"
             - name: Install Dependencies
               uses: nick-invision/retry@v2
               with:
@@ -79,7 +67,7 @@ jobs:
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
               with:
-                php-version: "7.4"
+                php-version: "8.0"
             - name: Install Dependencies
               uses: nick-invision/retry@v2
               with:
diff --git a/composer.json b/composer.json
index 541c6716f..974c1f274 100644
--- a/composer.json
+++ b/composer.json
@@ -9,17 +9,17 @@
     "docs": "https://googleapis.github.io/google-auth-library-php/main/"
   },
   "require": {
-    "php": ">=5.6",
+    "php": "^7.1||^8.0",
     "firebase/php-jwt": "~5.0",
     "guzzlehttp/guzzle": "^6.2.1|^7.0",
     "guzzlehttp/psr7": "^1.7|^2.0",
     "psr/http-message": "^1.0",
-    "psr/cache": "^1.0|^2.0"
+    "psr/cache": "^1.0|^2.0|^3.0"
   },
   "require-dev": {
     "guzzlehttp/promises": "0.1.1|^1.3",
     "squizlabs/php_codesniffer": "^3.5",
-    "phpunit/phpunit": "^5.7||^8.5.13",
+    "phpunit/phpunit": "^7.5||^8.5",
     "phpspec/prophecy-phpunit": "^1.1",
     "sebastian/comparator": ">=1.2.3",
     "phpseclib/phpseclib": "^2.0.31",
diff --git a/src/Cache/MemoryCacheItemPool.php b/src/Cache/MemoryCacheItemPool.php
index 1189e37c9..a02e39030 100644
--- a/src/Cache/MemoryCacheItemPool.php
+++ b/src/Cache/MemoryCacheItemPool.php
@@ -41,7 +41,7 @@ final class MemoryCacheItemPool implements CacheItemPoolInterface
      * @return CacheItemInterface
      *   The corresponding Cache Item.
      */
-    public function getItem($key)
+    public function getItem($key): CacheItemInterface
     {
         return current($this->getItems([$key]));
     }
@@ -49,18 +49,18 @@ public function getItem($key)
     /**
      * {@inheritdoc}
      *
-     * @return array
+     * @return iterable
      *   A traversable collection of Cache Items keyed by the cache keys of
      *   each item. A Cache item will be returned for each key, even if that
      *   key is not found. However, if no keys are specified then an empty
      *   traversable MUST be returned instead.
      */
-    public function getItems(array $keys = [])
+    public function getItems(array $keys = []): iterable
     {
         $items = [];
-
+        $itemClass = \PHP_VERSION_ID >= 80000 ? TypedItem::class : Item::class;
         foreach ($keys as $key) {
-            $items[$key] = $this->hasItem($key) ? clone $this->items[$key] : new Item($key);
+            $items[$key] = $this->hasItem($key) ? clone $this->items[$key] : new $itemClass($key);
         }
 
         return $items;
@@ -72,7 +72,7 @@ public function getItems(array $keys = [])
      * @return bool
      *   True if item exists in the cache, false otherwise.
      */
-    public function hasItem($key)
+    public function hasItem($key): bool
     {
         $this->isValidKey($key);
 
@@ -85,7 +85,7 @@ public function hasItem($key)
      * @return bool
      *   True if the pool was successfully cleared. False if there was an error.
      */
-    public function clear()
+    public function clear(): bool
     {
         $this->items = [];
         $this->deferredItems = [];
@@ -99,7 +99,7 @@ public function clear()
      * @return bool
      *   True if the item was successfully removed. False if there was an error.
      */
-    public function deleteItem($key)
+    public function deleteItem($key): bool
     {
         return $this->deleteItems([$key]);
     }
@@ -110,7 +110,7 @@ public function deleteItem($key)
      * @return bool
      *   True if the items were successfully removed. False if there was an error.
      */
-    public function deleteItems(array $keys)
+    public function deleteItems(array $keys): bool
     {
         array_walk($keys, [$this, 'isValidKey']);
 
@@ -127,7 +127,7 @@ public function deleteItems(array $keys)
      * @return bool
      *   True if the item was successfully persisted. False if there was an error.
      */
-    public function save(CacheItemInterface $item)
+    public function save(CacheItemInterface $item): bool
     {
         $this->items[$item->getKey()] = $item;
 
@@ -140,7 +140,7 @@ public function save(CacheItemInterface $item)
      * @return bool
      *   False if the item could not be queued or if a commit was attempted and failed. True otherwise.
      */
-    public function saveDeferred(CacheItemInterface $item)
+    public function saveDeferred(CacheItemInterface $item): bool
     {
         $this->deferredItems[$item->getKey()] = $item;
 
@@ -153,7 +153,7 @@ public function saveDeferred(CacheItemInterface $item)
      * @return bool
      *   True if all not-yet-saved items were successfully saved or there were none. False otherwise.
      */
-    public function commit()
+    public function commit(): bool
     {
         foreach ($this->deferredItems as $item) {
             $this->save($item);
diff --git a/src/Cache/SysVCacheItemPool.php b/src/Cache/SysVCacheItemPool.php
index 1834cf1b3..c552d8d2e 100644
--- a/src/Cache/SysVCacheItemPool.php
+++ b/src/Cache/SysVCacheItemPool.php
@@ -90,7 +90,7 @@ public function __construct($options = [])
         $this->sysvKey = ftok(__FILE__, $this->options['proj']);
     }
 
-    public function getItem($key)
+    public function getItem($key): CacheItemInterface
     {
         $this->loadItems();
         return current($this->getItems([$key]));
@@ -99,14 +99,15 @@ public function getItem($key)
     /**
      * {@inheritdoc}
      */
-    public function getItems(array $keys = [])
+    public function getItems(array $keys = []): iterable
     {
         $this->loadItems();
         $items = [];
+        $itemClass = \PHP_VERSION_ID >= 80000 ? TypedItem::class : Item::class;
         foreach ($keys as $key) {
             $items[$key] = $this->hasItem($key) ?
                 clone $this->items[$key] :
-                new Item($key);
+                new $itemClass($key);
         }
         return $items;
     }
@@ -114,7 +115,7 @@ public function getItems(array $keys = [])
     /**
      * {@inheritdoc}
      */
-    public function hasItem($key)
+    public function hasItem($key): bool
     {
         $this->loadItems();
         return isset($this->items[$key]) && $this->items[$key]->isHit();
@@ -123,7 +124,7 @@ public function hasItem($key)
     /**
      * {@inheritdoc}
      */
-    public function clear()
+    public function clear(): bool
     {
         $this->items = [];
         $this->deferredItems = [];
@@ -133,7 +134,7 @@ public function clear()
     /**
      * {@inheritdoc}
      */
-    public function deleteItem($key)
+    public function deleteItem($key): bool
     {
         return $this->deleteItems([$key]);
     }
@@ -141,7 +142,7 @@ public function deleteItem($key)
     /**
      * {@inheritdoc}
      */
-    public function deleteItems(array $keys)
+    public function deleteItems(array $keys): bool
     {
         if (!$this->hasLoadedItems) {
             $this->loadItems();
@@ -156,7 +157,7 @@ public function deleteItems(array $keys)
     /**
      * {@inheritdoc}
      */
-    public function save(CacheItemInterface $item)
+    public function save(CacheItemInterface $item): bool
     {
         if (!$this->hasLoadedItems) {
             $this->loadItems();
@@ -169,7 +170,7 @@ public function save(CacheItemInterface $item)
     /**
      * {@inheritdoc}
      */
-    public function saveDeferred(CacheItemInterface $item)
+    public function saveDeferred(CacheItemInterface $item): bool
     {
         $this->deferredItems[$item->getKey()] = $item;
         return true;
@@ -178,7 +179,7 @@ public function saveDeferred(CacheItemInterface $item)
     /**
      * {@inheritdoc}
      */
-    public function commit()
+    public function commit(): bool
     {
         foreach ($this->deferredItems as $item) {
             if ($this->save($item) === false) {
diff --git a/src/Cache/TypedItem.php b/src/Cache/TypedItem.php
new file mode 100644
index 000000000..7ad071068
--- /dev/null
+++ b/src/Cache/TypedItem.php
@@ -0,0 +1,187 @@
+<?php
+/*
+ * Copyright 2022 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace Google\Auth\Cache;
+
+use Psr\Cache\CacheItemInterface;
+
+/**
+ * A cache item.
+ */
+final class TypedItem implements CacheItemInterface
+{
+    /**
+     * @var mixed
+     */
+    private mixed $value;
+
+    /**
+     * @var \DateTime|null
+     */
+    private ?\DateTime $expiration;
+
+    /**
+     * @var bool
+     */
+    private bool $isHit = false;
+
+    /**
+     * @param string $key
+     */
+    public function __construct(
+        private string $key
+    ) {
+        $this->key = $key;
+        $this->expiration = null;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getKey(): string
+    {
+        return $this->key;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get(): mixed
+    {
+        return $this->isHit() ? $this->value : null;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isHit(): bool
+    {
+        if (!$this->isHit) {
+            return false;
+        }
+
+        if ($this->expiration === null) {
+            return true;
+        }
+
+        return $this->currentTime()->getTimestamp() < $this->expiration->getTimestamp();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function set(mixed $value): static
+    {
+        $this->isHit = true;
+        $this->value = $value;
+
+        return $this;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function expiresAt($expiration): static
+    {
+        if ($this->isValidExpiration($expiration)) {
+            $this->expiration = $expiration;
+
+            return $this;
+        }
+
+        $implementationMessage = interface_exists('DateTimeInterface')
+            ? 'implement interface DateTimeInterface'
+            : 'be an instance of DateTime';
+
+        $error = sprintf(
+            'Argument 1 passed to %s::expiresAt() must %s, %s given',
+            get_class($this),
+            $implementationMessage,
+            gettype($expiration)
+        );
+
+        $this->handleError($error);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function expiresAfter($time): static
+    {
+        if (is_int($time)) {
+            $this->expiration = $this->currentTime()->add(new \DateInterval("PT{$time}S"));
+        } elseif ($time instanceof \DateInterval) {
+            $this->expiration = $this->currentTime()->add($time);
+        } elseif ($time === null) {
+            $this->expiration = $time;
+        } else {
+            $message = 'Argument 1 passed to %s::expiresAfter() must be an ' .
+                       'instance of DateInterval or of the type integer, %s given';
+            $error = sprintf($message, get_class($this), gettype($time));
+
+            $this->handleError($error);
+        }
+
+        return $this;
+    }
+
+    /**
+     * Handles an error.
+     *
+     * @param string $error
+     * @throws \TypeError
+     */
+    private function handleError($error)
+    {
+        if (class_exists('TypeError')) {
+            throw new \TypeError($error);
+        }
+
+        trigger_error($error, \E_USER_ERROR);
+    }
+
+    /**
+     * Determines if an expiration is valid based on the rules defined by PSR6.
+     *
+     * @param mixed $expiration
+     * @return bool
+     */
+    private function isValidExpiration($expiration)
+    {
+        if ($expiration === null) {
+            return true;
+        }
+
+        // We test for two types here due to the fact the DateTimeInterface
+        // was not introduced until PHP 5.5. Checking for the DateTime type as
+        // well allows us to support 5.4.
+        if ($expiration instanceof \DateTimeInterface) {
+            return true;
+        }
+
+        if ($expiration instanceof \DateTime) {
+            return true;
+        }
+
+        return false;
+    }
+
+    protected function currentTime()
+    {
+        return new \DateTime('now', new \DateTimeZone('UTC'));
+    }
+}
diff --git a/tests/AccessTokenTest.php b/tests/AccessTokenTest.php
index 6299896c5..a6e66b1b8 100644
--- a/tests/AccessTokenTest.php
+++ b/tests/AccessTokenTest.php
@@ -289,9 +289,11 @@ public function testRetrieveCertsFromLocationLocalFile()
             ->shouldBeCalledTimes(1)
             ->willReturn(null);
         $item->set($certsData)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($item->reveal());
         $item->expiresAt(Argument::type('\DateTime'))
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($item->reveal());
 
         $this->cache->getItem('google_auth_certs_cache|' . sha1($certsLocation))
             ->shouldBeCalledTimes(1)
@@ -411,9 +413,11 @@ public function testRetrieveCertsFromLocationRemote()
             ->shouldBeCalledTimes(1)
             ->willReturn(null);
         $item->set($certsData)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($item->reveal());
         $item->expiresAt(Argument::type('\DateTime'))
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($item->reveal());
 
         $this->cache->getItem('google_auth_certs_cache|federated_signon_certs_v3')
             ->shouldBeCalledTimes(1)
diff --git a/tests/ApplicationDefaultCredentialsTest.php b/tests/ApplicationDefaultCredentialsTest.php
index a1655f5c1..75b50697b 100644
--- a/tests/ApplicationDefaultCredentialsTest.php
+++ b/tests/ApplicationDefaultCredentialsTest.php
@@ -140,7 +140,7 @@ public function testGceCredentials()
 
         // used default scope
         $tokenUri = $uriProperty->getValue($creds);
-        $this->assertContains('a+default+scope', $tokenUri);
+        $this->assertStringContainsString('a+default+scope', $tokenUri);
 
         $creds = ApplicationDefaultCredentials::getCredentials(
             'a+user+scope', // $scope
@@ -156,7 +156,7 @@ public function testGceCredentials()
 
         // did not use default scope
         $tokenUri = $uriProperty->getValue($creds);
-        $this->assertContains('a+user+scope', $tokenUri);
+        $this->assertStringContainsString('a+user+scope', $tokenUri);
     }
 
     /** @runInSeparateProcess */
@@ -396,9 +396,11 @@ public function testOnGceCacheWithoutHit()
         $mockCacheItem->isHit()
             ->willReturn(false);
         $mockCacheItem->set(true)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($mockCacheItem->reveal());
         $mockCacheItem->expiresAfter(1500)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($mockCacheItem->reveal());
 
         $mockCache = $this->prophesize('Psr\Cache\CacheItemPoolInterface');
         $mockCache->getItem(GCECache::GCE_CACHE_KEY)
@@ -433,9 +435,11 @@ public function testOnGceCacheWithOptions()
         $mockCacheItem->isHit()
             ->willReturn(false);
         $mockCacheItem->set(true)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($mockCacheItem->reveal());
         $mockCacheItem->expiresAfter($lifetime)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($mockCacheItem->reveal());
 
         $mockCache = $this->prophesize('Psr\Cache\CacheItemPoolInterface');
         $mockCache->getItem($prefix . GCECache::GCE_CACHE_KEY)
diff --git a/tests/BaseTest.php b/tests/BaseTest.php
index 26b127dc1..e38e3edf1 100644
--- a/tests/BaseTest.php
+++ b/tests/BaseTest.php
@@ -41,4 +41,13 @@ public function getValidKeyName($key)
     {
         return preg_replace('|[^a-zA-Z0-9_\.! ]|', '', $key);
     }
+
+    protected function getCacheItemClass()
+    {
+        if (\PHP_VERSION_ID >= 80000) {
+            return 'Google\Auth\Cache\TypedItem';
+        }
+
+        return 'Google\Auth\Cache\Item';
+    }
 }
diff --git a/tests/Cache/ItemTest.php b/tests/Cache/ItemTest.php
index 9312d82ad..8917f8b32 100644
--- a/tests/Cache/ItemTest.php
+++ b/tests/Cache/ItemTest.php
@@ -18,12 +18,17 @@
 namespace Google\Auth\Tests\Cache;
 
 use Google\Auth\Cache\Item;
+use Google\Auth\Cache\TypedItem;
 use PHPUnit\Framework\TestCase;
 
 class ItemTest extends TestCase
 {
     public function getItem($key)
     {
+        if (\PHP_VERSION_ID >= 80000) {
+            return new TypedItem($key);
+        }
+
         return new Item($key);
     }
 
diff --git a/tests/Cache/MemoryCacheItemPoolTest.php b/tests/Cache/MemoryCacheItemPoolTest.php
index 056369089..6a8aff038 100644
--- a/tests/Cache/MemoryCacheItemPoolTest.php
+++ b/tests/Cache/MemoryCacheItemPoolTest.php
@@ -18,10 +18,10 @@
 namespace Google\Auth\Tests\Cache;
 
 use Google\Auth\Cache\MemoryCacheItemPool;
-use PHPUnit\Framework\TestCase;
+use Google\Auth\Tests\BaseTest;
 use Psr\Cache\InvalidArgumentException;
 
-class MemoryCacheItemPoolTest extends TestCase
+class MemoryCacheItemPoolTest extends BaseTest
 {
     private $pool;
 
@@ -43,7 +43,7 @@ public function testGetsFreshItem()
     {
         $item = $this->pool->getItem('item');
 
-        $this->assertInstanceOf('Google\Auth\Cache\Item', $item);
+        $this->assertInstanceOf($this->getCacheItemClass(), $item);
         $this->assertNull($item->get());
         $this->assertFalse($item->isHit());
     }
@@ -55,7 +55,7 @@ public function testGetsExistingItem()
         $this->saveItem($key, $value);
         $item = $this->pool->getItem($key);
 
-        $this->assertInstanceOf('Google\Auth\Cache\Item', $item);
+        $this->assertInstanceOf($this->getCacheItemClass(), $item);
         $this->assertEquals($value, $item->get());
         $this->assertTrue($item->isHit());
     }
@@ -66,7 +66,7 @@ public function testGetsMultipleItems()
         $items = $this->pool->getItems($keys);
 
         $this->assertEquals($keys, array_keys($items));
-        $this->assertContainsOnlyInstancesOf('Google\Auth\Cache\Item', $items);
+        $this->assertContainsOnlyInstancesOf($this->getCacheItemClass(), $items);
     }
 
     public function testHasItem()
diff --git a/tests/Cache/SysVCacheItemPoolTest.php b/tests/Cache/SysVCacheItemPoolTest.php
index 902b9c2b4..46f7812c1 100644
--- a/tests/Cache/SysVCacheItemPoolTest.php
+++ b/tests/Cache/SysVCacheItemPoolTest.php
@@ -18,9 +18,9 @@
 namespace Google\Auth\Tests\Cache;
 
 use Google\Auth\Cache\SysVCacheItemPool;
-use PHPUnit\Framework\TestCase;
+use Google\Auth\Tests\BaseTest;
 
-class SysVCacheItemPoolTest extends TestCase
+class SysVCacheItemPoolTest extends BaseTest
 {
     private $pool;
 
@@ -48,7 +48,7 @@ public function testGetsFreshItem()
     {
         $item = $this->pool->getItem('item');
 
-        $this->assertInstanceOf('Google\Auth\Cache\Item', $item);
+        $this->assertInstanceOf($this->getCacheItemClass(), $item);
         $this->assertNull($item->get());
         $this->assertFalse($item->isHit());
     }
@@ -70,7 +70,7 @@ public function testGetsExistingItem()
         $this->saveItem($key, $value);
         $item = $this->pool->getItem($key);
 
-        $this->assertInstanceOf('Google\Auth\Cache\Item', $item);
+        $this->assertInstanceOf($this->getCacheItemClass(), $item);
         $this->assertEquals($value, $item->get());
         $this->assertTrue($item->isHit());
     }
@@ -81,7 +81,7 @@ public function testGetsMultipleItems()
         $items = $this->pool->getItems($keys);
 
         $this->assertEquals($keys, array_keys($items));
-        $this->assertContainsOnlyInstancesOf('Google\Auth\Cache\Item', $items);
+        $this->assertContainsOnlyInstancesOf($this->getCacheItemClass(), $items);
     }
 
     public function testHasItem()
diff --git a/tests/Cache/sysv_cache_creator.php b/tests/Cache/sysv_cache_creator.php
index 618097d23..3231c4301 100644
--- a/tests/Cache/sysv_cache_creator.php
+++ b/tests/Cache/sysv_cache_creator.php
@@ -21,10 +21,15 @@
 
 use Google\Auth\Cache\Item;
 use Google\Auth\Cache\SysVCacheItemPool;
+use Google\Auth\Cache\TypedItem;
 
 $value = $argv[1];
 // Use the same variableKey in the test.
 $pool = new SysVCacheItemPool(['variableKey' => 99]);
-$item = new Item('separate-process-item');
+if (\PHP_VERSION_ID >= 80000) {
+    $item = new TypedItem('separate-process-item');
+} else {
+    $item = new Item('separate-process-item');
+}
 $item->set($value);
 $pool->save($item);
diff --git a/tests/CacheTraitTest.php b/tests/CacheTraitTest.php
index a83019076..ac93eb5de 100644
--- a/tests/CacheTraitTest.php
+++ b/tests/CacheTraitTest.php
@@ -128,9 +128,11 @@ public function testSuccessfullySetsToCache()
     {
         $value = '1234';
         $this->mockCacheItem->set($value)
-            ->shouldBeCalled();
+            ->shouldBeCalled()
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter(Argument::any())
-            ->shouldBeCalled();
+            ->shouldBeCalled()
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem('key')
             ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->save(Argument::type('Psr\Cache\CacheItemInterface'))
diff --git a/tests/Credentials/ServiceAccountCredentialsTest.php b/tests/Credentials/ServiceAccountCredentialsTest.php
index af8896388..9546ee5d7 100644
--- a/tests/Credentials/ServiceAccountCredentialsTest.php
+++ b/tests/Credentials/ServiceAccountCredentialsTest.php
@@ -660,10 +660,10 @@ public function testUpdateMetadataWithScopeAndUseJwtAccessWithScopeParameter()
         );
 
         $authorization = $actual_metadata[CredentialsLoader::AUTH_METADATA_KEY];
-        $this->assertInternalType('array', $authorization);
+        $this->assertTrue(is_array($authorization));
 
         $bearer_token = current($authorization);
-        $this->assertInternalType('string', $bearer_token);
+        $this->assertTrue(is_string($bearer_token));
         $this->assertEquals(0, strpos($bearer_token, 'Bearer '));
 
         // Ensure scopes are signed inside
@@ -671,7 +671,7 @@ public function testUpdateMetadataWithScopeAndUseJwtAccessWithScopeParameter()
         $this->assertEquals(2, substr_count($token, '.'));
         list($header, $payload, $sig) = explode('.', $bearer_token);
         $json = json_decode(base64_decode($payload), true);
-        $this->assertInternalType('array', $json);
+        $this->assertTrue(is_array($json));
         $this->assertArrayHasKey('scope', $json);
         $this->assertEquals($json['scope'], $scope);
     }
@@ -699,10 +699,10 @@ public function testUpdateMetadataWithScopeAndUseJwtAccessWithScopeParameterAndA
         );
 
         $authorization = $actual_metadata[CredentialsLoader::AUTH_METADATA_KEY];
-        $this->assertInternalType('array', $authorization);
+        $this->assertTrue(is_array($authorization));
 
         $bearer_token = current($authorization);
-        $this->assertInternalType('string', $bearer_token);
+        $this->assertTrue(is_string($bearer_token));
         $this->assertEquals(0, strpos($bearer_token, 'Bearer '));
 
         // Ensure scopes are signed inside
@@ -710,13 +710,13 @@ public function testUpdateMetadataWithScopeAndUseJwtAccessWithScopeParameterAndA
         $this->assertEquals(2, substr_count($token, '.'));
         list($header, $payload, $sig) = explode('.', $bearer_token);
         $json = json_decode(base64_decode($payload), true);
-        $this->assertInternalType('array', $json);
+        $this->assertTrue(is_array($json));
         $this->assertArrayHasKey('scope', $json);
         $this->assertEquals($json['scope'], implode(' ', $scope));
 
         // Test last received token
         $cachedToken = $sa->getLastReceivedToken();
-        $this->assertInternalType('array', $cachedToken);
+        $this->assertTrue(is_array($cachedToken));
         $this->assertArrayHasKey('access_token', $cachedToken);
         $this->assertEquals($token, $cachedToken['access_token']);
     }
@@ -734,7 +734,7 @@ public function testFetchAuthTokenWithScopeAndUseJwtAccessWithScopeParameter()
         $sa->useJwtAccessWithScope();
 
         $access_token = $sa->fetchAuthToken();
-        $this->assertInternalType('array', $access_token);
+        $this->assertTrue(is_array($access_token));
         $this->assertArrayHasKey('access_token', $access_token);
         $token = $access_token['access_token'];
 
@@ -742,7 +742,7 @@ public function testFetchAuthTokenWithScopeAndUseJwtAccessWithScopeParameter()
         $this->assertEquals(2, substr_count($token, '.'));
         list($header, $payload, $sig) = explode('.', $token);
         $json = json_decode(base64_decode($payload), true);
-        $this->assertInternalType('array', $json);
+        $this->assertTrue(is_array($json));
         $this->assertArrayHasKey('scope', $json);
         $this->assertEquals($json['scope'], $scope);
     }
@@ -760,7 +760,7 @@ public function testFetchAuthTokenWithScopeAndUseJwtAccessWithScopeParameterAndA
         $sa->useJwtAccessWithScope();
 
         $access_token = $sa->fetchAuthToken();
-        $this->assertInternalType('array', $access_token);
+        $this->assertTrue(is_array($access_token));
         $this->assertArrayHasKey('access_token', $access_token);
         $token = $access_token['access_token'];
 
@@ -768,13 +768,13 @@ public function testFetchAuthTokenWithScopeAndUseJwtAccessWithScopeParameterAndA
         $this->assertEquals(2, substr_count($token, '.'));
         list($header, $payload, $sig) = explode('.', $token);
         $json = json_decode(base64_decode($payload), true);
-        $this->assertInternalType('array', $json);
+        $this->assertTrue(is_array($json));
         $this->assertArrayHasKey('scope', $json);
         $this->assertEquals($json['scope'], implode(' ', $scope));
 
         // Test last received token
         $cachedToken = $sa->getLastReceivedToken();
-        $this->assertInternalType('array', $cachedToken);
+        $this->assertTrue(is_array($cachedToken));
         $this->assertArrayHasKey('access_token', $cachedToken);
         $this->assertEquals($token, $cachedToken['access_token']);
     }
diff --git a/tests/CredentialsLoaderTest.php b/tests/CredentialsLoaderTest.php
index 64222d7d1..770d9195a 100644
--- a/tests/CredentialsLoaderTest.php
+++ b/tests/CredentialsLoaderTest.php
@@ -103,8 +103,8 @@ public function testActualDefaultClientCertSource()
         }
         $creds = $clientCertSource();
         $this->assertTrue(is_string($creds));
-        $this->assertContains('-----BEGIN CERTIFICATE-----', $creds);
-        $this->assertContains('-----BEGIN PRIVATE KEY-----', $creds);
+        $this->assertStringContainsString('-----BEGIN CERTIFICATE-----', $creds);
+        $this->assertStringContainsString('-----BEGIN PRIVATE KEY-----', $creds);
     }
 
     /**
diff --git a/tests/FetchAuthTokenCacheTest.php b/tests/FetchAuthTokenCacheTest.php
index 566721e1a..088540d34 100644
--- a/tests/FetchAuthTokenCacheTest.php
+++ b/tests/FetchAuthTokenCacheTest.php
@@ -157,9 +157,11 @@ public function testUpdateMetadataWithoutCache()
             ->shouldBeCalled()
             ->willReturn($value);
         $this->mockCacheItem->set($value)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter(1500)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->save($this->mockCacheItem)
             ->shouldBeCalledTimes(1);
         $this->mockFetcher->updateMetadata(Argument::type('array'), null, null)
@@ -299,9 +301,11 @@ public function testShouldNotReturnValueWhenExpired()
             ->shouldBeCalledTimes(1)
             ->willReturn($cachedValue);
         $this->mockCacheItem->set($newToken)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter(1500)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($cacheKey)
             ->shouldBeCalledTimes(2)
             ->willReturn($this->mockCacheItem->reveal());
@@ -368,9 +372,10 @@ public function testShouldSaveValueInCacheWithCacheOptions()
             ->willReturn(false);
         $this->mockCacheItem->set($cachedValue)
             ->shouldBeCalledTimes(1)
-            ->willReturn(false);
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter($lifetime)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($prefix . $cacheKey)
             ->shouldBeCalledTimes(2)
             ->willReturn($this->mockCacheItem->reveal());
diff --git a/tests/GCECacheTest.php b/tests/GCECacheTest.php
index d735932e3..d91804013 100644
--- a/tests/GCECacheTest.php
+++ b/tests/GCECacheTest.php
@@ -86,9 +86,11 @@ public function testUncached()
             ->shouldBeCalledTimes(1)
             ->willReturn(false);
         $this->mockCacheItem->set(true)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter(1500)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem(GCECache::GCE_CACHE_KEY)
             ->shouldBeCalledTimes(2)
             ->willReturn($this->mockCacheItem->reveal());
@@ -139,9 +141,11 @@ public function testShouldSaveValueInCacheWithCacheOptions()
         $this->mockCacheItem->isHit()
             ->willReturn(false);
         $this->mockCacheItem->set(true)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter($lifetime)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($prefix . GCECache::GCE_CACHE_KEY)
             ->shouldBeCalledTimes(2)
             ->willReturn($this->mockCacheItem->reveal());
diff --git a/tests/Middleware/AuthTokenMiddlewareTest.php b/tests/Middleware/AuthTokenMiddlewareTest.php
index 8b09156cf..a9e7aa6ec 100644
--- a/tests/Middleware/AuthTokenMiddlewareTest.php
+++ b/tests/Middleware/AuthTokenMiddlewareTest.php
@@ -220,9 +220,10 @@ public function testShouldSaveValueInCacheWithSpecifiedPrefix()
             ->willReturn(false);
         $this->mockCacheItem->set($cachedValue)
             ->shouldBeCalledTimes(1)
-            ->willReturn(false);
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter($lifetime)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($prefix . $cacheKey)
             ->shouldBeCalled()
             ->willReturn($this->mockCacheItem->reveal());
@@ -264,9 +265,11 @@ public function testShouldNotifyTokenCallback(callable $tokenCallback)
         $this->mockCacheItem->isHit()
             ->willReturn(false);
         $this->mockCacheItem->set($cachedValue)
-            ->shouldBeCalled();
+            ->shouldBeCalled()
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter(Argument::any())
-            ->shouldBeCalled();
+            ->shouldBeCalled()
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($prefix . $cacheKey)
             ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->save(Argument::type('Psr\Cache\CacheItemInterface'))
diff --git a/tests/Middleware/ScopedAccessTokenMiddlewareTest.php b/tests/Middleware/ScopedAccessTokenMiddlewareTest.php
index 34dcce488..a7b31650a 100644
--- a/tests/Middleware/ScopedAccessTokenMiddlewareTest.php
+++ b/tests/Middleware/ScopedAccessTokenMiddlewareTest.php
@@ -140,9 +140,10 @@ public function testShouldSaveValueInCache()
             ->willReturn(false);
         $this->mockCacheItem->set($token)
             ->shouldBeCalledTimes(1)
-            ->willReturn(false);
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter(Argument::any())
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($this->getValidKeyName(self::TEST_SCOPE))
             ->shouldBeCalledTimes(2)
             ->willReturn($this->mockCacheItem->reveal());
@@ -178,9 +179,10 @@ public function testShouldSaveValueInCacheWithCacheOptions()
             ->willReturn(false);
         $this->mockCacheItem->set($token)
             ->shouldBeCalledTimes(1)
-            ->willReturn(false);
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCacheItem->expiresAfter($lifetime)
-            ->shouldBeCalledTimes(1);
+            ->shouldBeCalledTimes(1)
+            ->willReturn($this->mockCacheItem->reveal());
         $this->mockCache->getItem($prefix . $this->getValidKeyName(self::TEST_SCOPE))
             ->shouldBeCalledTimes(2)
             ->willReturn($this->mockCacheItem->reveal());