diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 9200386..9d9de87 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -17,7 +17,7 @@ jobs:
                     # - "7.4" Disabled due to https://github.com/composer/composer/issues/10387, which did not resolve the issue here somehow
                     - "8.0"
                     - "8.1"
-
+                    - "8.2"
         steps:
             - name: "Checkout"
               uses: "actions/checkout@v2"
diff --git a/.gitignore b/.gitignore
index 82b50a4..cb6917c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,4 @@
 /vendor
 phpunit.xml
 composer.lock
-.phpunit.result.cache
+.phpunit.cache/
diff --git a/README.md b/README.md
index a48ef3d..f0c8bbb 100644
--- a/README.md
+++ b/README.md
@@ -43,12 +43,12 @@ Note that, as this is not a tool intended for production, it should be required
 - gettimeofday()  
 - gmdate()
 - gmmktime()
-- gmstrftime()
+- gmstrftime() (DEPRECATED starting from PHP 8.1)
 - idate()
 - localtime()
 - microtime()
 - mktime()
-- strftime()  
+- strftime() (DEPRECATED starting from PHP 8.1)
 - strtotime()
 - time()
 - unixtojd()
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 4420dee..19ef876 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,15 +1,13 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
          bootstrap="vendor/autoload.php"
          processIsolation="false"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
-    <testsuites>
-        <testsuite name="Tests">
-            <directory>tests</directory>
-        </testsuite>
-    </testsuites>
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.1/phpunit.xsd"
+         cacheDirectory=".phpunit.cache">
+  <testsuites>
+    <testsuite name="Tests">
+      <directory>tests</directory>
+    </testsuite>
+  </testsuites>
 </phpunit>
diff --git a/src/ClockMock.php b/src/ClockMock.php
index 740ccb8..a53cff2 100644
--- a/src/ClockMock.php
+++ b/src/ClockMock.php
@@ -86,12 +86,10 @@ public static function reset(): void
         uopz_unset_return('gettimeofday');
         uopz_unset_return('gmdate');
         uopz_unset_return('gmmktime');
-        uopz_unset_return('gmstrftime');
         uopz_unset_return('idate');
         uopz_unset_return('localtime');
         uopz_unset_return('microtime');
         uopz_unset_return('mktime');
-        uopz_unset_return('strftime');
         uopz_unset_return('strtotime');
         uopz_unset_return('time');
         uopz_unset_return(\DateTime::class, 'createFromFormat');
@@ -101,6 +99,14 @@ public static function reset(): void
             uopz_unset_return('unixtojd');
         }
 
+        // The following two are deprecated -- prepare for removal in PHP 9.0
+        if (function_exists('gmstrftime')) {
+            uopz_unset_return('gmstrftime');
+        }
+        if (function_exists('strftime')) {
+            uopz_unset_return('strftime');
+        }
+
         uopz_unset_mock(\DateTime::class);
         uopz_unset_mock(\DateTimeImmutable::class);
 
@@ -123,12 +129,10 @@ private static function activateMocksIfNeeded(): void
         uopz_set_return('gettimeofday', self::mock_gettimeofday(), true);
         uopz_set_return('gmdate', self::mock_gmdate(), true);
         uopz_set_return('gmmktime', self::mock_gmmktime(), true);
-        uopz_set_return('gmstrftime', self::mock_gmstrftime(), true);
         uopz_set_return('idate', self::mock_idate(), true);
         uopz_set_return('localtime', self::mock_localtime(), true);
         uopz_set_return('microtime', self::mock_microtime(), true);
         uopz_set_return('mktime', self::mock_mktime(), true);
-        uopz_set_return('strftime', self::mock_strftime(), true);
         uopz_set_return('strtotime', self::mock_strtotime(), true);
         uopz_set_return('time', self::mock_time(), true);
 
@@ -136,6 +140,14 @@ private static function activateMocksIfNeeded(): void
             uopz_set_return('unixtojd', self::mock_unixtojd(), true);
         }
 
+        // The following two are deprecated -- prepare for removal in PHP 9.0
+        if (function_exists('gmstrftime')) {
+            uopz_set_return('gmstrftime', self::mock_gmstrftime(), true);
+        }
+        if (function_exists('strftime')) {
+            uopz_set_return('strftime', self::mock_strftime(), true);
+        }
+
         uopz_set_mock(\DateTime::class, DateTimeMock::class);
         uopz_set_return(\DateTime::class, 'createFromFormat', self::mock_date_create_from_format(), true);
         uopz_set_mock(\DateTimeImmutable::class, DateTimeImmutableMock::class);
diff --git a/test b/test
deleted file mode 100644
index e69de29..0000000
diff --git a/tests/ClockMockTest.php b/tests/ClockMockTest.php
index c4d4c35..c835a4a 100644
--- a/tests/ClockMockTest.php
+++ b/tests/ClockMockTest.php
@@ -282,7 +282,7 @@ public function test_getdate()
         );
     }
 
-    public function dataProvider_gettimeofday(): array
+    public static function dataProvider_gettimeofday(): array
     {
         return [
             ['2022-04-04 14:26:29.123456', 'UTC', [1649082389, 123456, 0, 0]],
@@ -323,7 +323,7 @@ public function test_gmstrftime()
         $this->assertEquals('2022-04-04 11:26:29', gmstrftime('%F %T'));
     }
 
-    public function dateProvider_gmmktime(): array
+    public static function dataProvider_gmmktime(): array
     {
         // NOTE: for all datasets, hour in freezeDateTime is completely irrelevant because always overridden by $hour
         // parameter provided to gmmktime. Also, in expectedDateTime hour is always "13" because hour 10 in GMT
@@ -368,7 +368,7 @@ public function dateProvider_gmmktime(): array
     }
 
     /**
-     * @dataProvider dateProvider_gmmktime
+     * @dataProvider dataProvider_gmmktime
      */
     public function test_gmmktime(string $freezeDateTime, array $mktimeArgs, string $expectedDateTime)
     {
@@ -443,7 +443,7 @@ public function test_strftime()
         $this->assertEquals('2022-04-04 14:26:29', strftime('%F %T'));
     }
 
-    public function dateProvider_mktime(): array
+    public static function dataProvider_mktime(): array
     {
         return [
             [
@@ -485,7 +485,7 @@ public function dateProvider_mktime(): array
     }
 
     /**
-     * @dataProvider dateProvider_mktime
+     * @dataProvider dataProvider_mktime
      */
     public function test_mktime(string $freezeDateTime, array $mktimeArgs, string $expectedDateTime)
     {