diff --git a/tests/framework/ChangeLogTest.php b/tests/framework/ChangeLogTest.php
index 52bccb4c1b..479b530df1 100644
--- a/tests/framework/ChangeLogTest.php
+++ b/tests/framework/ChangeLogTest.php
@@ -18,7 +18,7 @@ use yiiunit\TestCase;
  */
 class ChangeLogTest extends TestCase
 {
-    public function changeProvider()
+    public static function changeProvider(): array
     {
         $lines = preg_split('~\R~', file_get_contents(__DIR__ . '/../../framework/CHANGELOG.md'), -1, PREG_SPLIT_NO_EMPTY);
 
diff --git a/tests/framework/base/ActionFilterTest.php b/tests/framework/base/ActionFilterTest.php
index 2340e30f64..2364746ce3 100644
--- a/tests/framework/base/ActionFilterTest.php
+++ b/tests/framework/base/ActionFilterTest.php
@@ -90,7 +90,7 @@ class ActionFilterTest extends TestCase
         $this->assertEquals([1, 3, 2], $controller->result);
     }
 
-    public function actionFilterProvider()
+    public static function actionFilterProvider(): array
     {
         return [
             [['class' => 'yii\filters\AccessControl', 'user' => 'yiiunit\framework\base\MockUser']],
diff --git a/tests/framework/base/ControllerTest.php b/tests/framework/base/ControllerTest.php
index ce97daf76b..0491239ec2 100644
--- a/tests/framework/base/ControllerTest.php
+++ b/tests/framework/base/ControllerTest.php
@@ -68,7 +68,7 @@ class ControllerTest extends TestCase
         $this->assertEquals($expectedActionMethod, $actionMethod);
     }
 
-    public function createInlineActionProvider()
+    public static function createInlineActionProvider(): array
     {
         return [
             ['\yiiunit\framework\base\TestController', 'non-existent-id', null],
@@ -91,7 +91,7 @@ class ControllerTest extends TestCase
         $this->assertSame($expected, preg_match('/^(?:[a-z0-9_]+-)*[a-z0-9_]+$/', $input));
     }
 
-    public function actionIdMethodProvider()
+    public static function actionIdMethodProvider(): array
     {
         return [
             ['apple-id', 1],
diff --git a/tests/framework/base/SecurityTest.php b/tests/framework/base/SecurityTest.php
index 365ba6bae5..9f976fd619 100644
--- a/tests/framework/base/SecurityTest.php
+++ b/tests/framework/base/SecurityTest.php
@@ -182,7 +182,7 @@ TEXT;
         }
     }
 
-    public function dataProviderEncryptByKeyCompat()
+    public static function dataProviderEncryptByKeyCompat(): array
     {
         // these ciphertexts generated using Yii 2.0.2 which is based on mcrypt.
         $mcrypt = [
@@ -493,7 +493,7 @@ TEXT;
         $this->assertEquals($data, $this->security->decryptByKey($encrypted, $key));
     }
 
-    public function dataProviderEncryptByPasswordCompat()
+    public static function dataProviderEncryptByPasswordCompat(): array
     {
         // these ciphertexts generated using Yii 2.0.2 which is based on mcrypt.
         $mcrypt = [
@@ -803,7 +803,7 @@ TEXT;
         $this->assertEquals($data, $this->security->decryptByPassword($encrypted, $password));
     }
 
-    public function randomKeyInvalidInputs()
+    public static function randomKeyInvalidInputs(): array
     {
         return [
             [0],
@@ -873,7 +873,7 @@ TEXT;
         $this->assertEquals(1, preg_match('/[A-Za-z0-9_-]+/', $key));
     }
 
-    public function dataProviderPbkdf2()
+    public static function dataProviderPbkdf2(): array
     {
         return array_filter([
             [
@@ -968,7 +968,7 @@ TEXT;
         $this->assertEquals($okm, bin2hex($DK));
     }
 
-    public function dataProviderDeriveKey()
+    public static function dataProviderDeriveKey(): array
     {
         // See Appendix A in https://tools.ietf.org/html/rfc5869
         return [
@@ -1061,7 +1061,7 @@ TEXT;
         $this->assertEquals($okm, bin2hex($dk));
     }
 
-    public function dataProviderCompareStrings()
+    public static function dataProviderCompareStrings(): array
     {
         return [
             ['', ''],
@@ -1120,7 +1120,7 @@ TEXT;
     /**
      * @return array
      */
-    public function maskProvider()
+    public static function maskProvider(): array
     {
         return [
             ['1'],
diff --git a/tests/framework/behaviors/AttributeBehaviorTest.php b/tests/framework/behaviors/AttributeBehaviorTest.php
index 5266ba8f86..2d9f2a8ad6 100644
--- a/tests/framework/behaviors/AttributeBehaviorTest.php
+++ b/tests/framework/behaviors/AttributeBehaviorTest.php
@@ -66,7 +66,7 @@ class AttributeBehaviorTest extends TestCase
     /**
      * @return array
      */
-    public function preserveNonEmptyValuesDataProvider()
+    public static function preserveNonEmptyValuesDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/behaviors/AttributesBehaviorTest.php b/tests/framework/behaviors/AttributesBehaviorTest.php
index 3be2d584ac..c52faeda47 100644
--- a/tests/framework/behaviors/AttributesBehaviorTest.php
+++ b/tests/framework/behaviors/AttributesBehaviorTest.php
@@ -66,7 +66,7 @@ class AttributesBehaviorTest extends TestCase
     /**
      * @return array
      */
-    public function preserveNonEmptyValuesDataProvider()
+    public static function preserveNonEmptyValuesDataProvider(): array
     {
         return [
             [
@@ -121,7 +121,7 @@ class AttributesBehaviorTest extends TestCase
     /**
      * @return array
      */
-    public function orderProvider()
+    public static function orderProvider(): array
     {
         return [
             [
diff --git a/tests/framework/behaviors/TimestampBehaviorTest.php b/tests/framework/behaviors/TimestampBehaviorTest.php
index bf1e6da74c..f9c05775a5 100644
--- a/tests/framework/behaviors/TimestampBehaviorTest.php
+++ b/tests/framework/behaviors/TimestampBehaviorTest.php
@@ -130,7 +130,7 @@ class TimestampBehaviorTest extends TestCase
         $model->save(false);
     }
 
-    public function expressionProvider()
+    public static function expressionProvider(): array
     {
         return [
             [
@@ -142,7 +142,7 @@ class TimestampBehaviorTest extends TestCase
             [new Expression("strftime('%Y')"), date('Y')],
             ['2015-10-20', '2015-10-20'],
             [time(), time()],
-            [[$this, 'arrayCallable'], '2015-10-20'],
+            [[null, 'arrayCallable'], '2015-10-20'],
         ];
     }
 
@@ -153,6 +153,10 @@ class TimestampBehaviorTest extends TestCase
      */
     public function testNewRecordExpression($expression, $expected): void
     {
+        if (is_array($expression)) {
+            $expression[0] ??= $this;
+        }
+
         ActiveRecordTimestamp::$tableName = 'test_auto_timestamp_string';
         ActiveRecordTimestamp::$behaviors = [
             'timestamp' => [
diff --git a/tests/framework/caching/CacheTestCase.php b/tests/framework/caching/CacheTestCase.php
index 8147daa912..1f8113b6c2 100644
--- a/tests/framework/caching/CacheTestCase.php
+++ b/tests/framework/caching/CacheTestCase.php
@@ -107,7 +107,7 @@ abstract class CacheTestCase extends TestCase
     /**
      * @return array testing multiSet with and without expiry
      */
-    public function multiSetExpiry()
+    public static function multiSetExpiry(): array
     {
         return [[0], [2]];
     }
diff --git a/tests/framework/console/RequestTest.php b/tests/framework/console/RequestTest.php
index af90715a47..dd228d4560 100644
--- a/tests/framework/console/RequestTest.php
+++ b/tests/framework/console/RequestTest.php
@@ -16,7 +16,7 @@ use yiiunit\TestCase;
  */
 class RequestTest extends TestCase
 {
-    public function provider()
+    public static function provider(): array
     {
         return [
             [
diff --git a/tests/framework/console/UnknownCommandExceptionTest.php b/tests/framework/console/UnknownCommandExceptionTest.php
index 179ba23d87..2318fc6c1a 100644
--- a/tests/framework/console/UnknownCommandExceptionTest.php
+++ b/tests/framework/console/UnknownCommandExceptionTest.php
@@ -32,7 +32,7 @@ class UnknownCommandExceptionTest extends TestCase
         ]);
     }
 
-    public function suggestedCommandsProvider()
+    public static function suggestedCommandsProvider(): array
     {
         return [
             ['migate', ['migrate']],
diff --git a/tests/framework/console/controllers/AssetControllerTest.php b/tests/framework/console/controllers/AssetControllerTest.php
index 704873c4c7..77b25bf4ed 100644
--- a/tests/framework/console/controllers/AssetControllerTest.php
+++ b/tests/framework/console/controllers/AssetControllerTest.php
@@ -466,7 +466,7 @@ EOL;
      * Data provider for [[testAdjustCssUrl()]].
      * @return array test data.
      */
-    public function adjustCssUrlDataProvider()
+    public static function adjustCssUrlDataProvider(): array
     {
         return [
             [
@@ -585,7 +585,7 @@ EOL;
      * Data provider for [[testFindRealPath()]].
      * @return array test data
      */
-    public function findRealPathDataProvider()
+    public static function findRealPathDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/console/controllers/MigrateControllerTest.php b/tests/framework/console/controllers/MigrateControllerTest.php
index c9e3014785..0536ef8cf4 100644
--- a/tests/framework/console/controllers/MigrateControllerTest.php
+++ b/tests/framework/console/controllers/MigrateControllerTest.php
@@ -159,7 +159,7 @@ class MigrateControllerTest extends TestCase
     /**
      * @return array
      */
-    public function generateMigrationDataProvider()
+    public static function generateMigrationDataProvider(): array
     {
         $params = [
             'create_fields' => [
@@ -359,7 +359,7 @@ class MigrateControllerTest extends TestCase
     /**
      * @return array
      */
-    public function generateJunctionMigrationDataProvider()
+    public static function generateJunctionMigrationDataProvider(): array
     {
         return [
             ['create_junction_post_and_tag_tables', 'post_tag', 'post', 'tag'],
@@ -487,7 +487,7 @@ class MigrateControllerTest extends TestCase
         $this->assertStringContainsString('No new migrations found. Your system is up-to-date.', $result);
     }
 
-    public function refreshMigrationDataProvider()
+    public static function refreshMigrationDataProvider(): array
     {
         return [
             ['default'],
diff --git a/tests/framework/console/controllers/PHPMessageControllerTest.php b/tests/framework/console/controllers/PHPMessageControllerTest.php
index 9551eecce2..61b874397e 100644
--- a/tests/framework/console/controllers/PHPMessageControllerTest.php
+++ b/tests/framework/console/controllers/PHPMessageControllerTest.php
@@ -124,7 +124,7 @@ class PHPMessageControllerTest extends BaseMessageControllerTest
         $this->assertEqualsWithoutLE($expected, $head);
     }
 
-    public function messageFileCategoriesDataProvider()
+    public static function messageFileCategoriesDataProvider(): array
     {
         return [
             'removeUnused:false - unused category should not be removed - normal category' => ['test_delete_category', true, false, true],
diff --git a/tests/framework/console/widgets/TableTest.php b/tests/framework/console/widgets/TableTest.php
index 431f1afcf7..312cad9da0 100644
--- a/tests/framework/console/widgets/TableTest.php
+++ b/tests/framework/console/widgets/TableTest.php
@@ -23,7 +23,7 @@ class TableTest extends TestCase
         $this->mockApplication();
     }
 
-    public function getTableData()
+    public static function getTableData(): array
     {
         return [
             [
@@ -69,7 +69,7 @@ EXPECTED;
         $this->assertEqualsWithoutLE($expected, $tableContent);
     }
 
-    public function getMultiLineTableData()
+    public static function getMultiLineTableData(): array
     {
         return [
             [
@@ -138,7 +138,7 @@ EXPECTED;
         $this->assertEqualsWithoutLE($expected, $tableContent);
     }
 
-    public function getNumericTableData()
+    public static function getNumericTableData(): array
     {
         return [
             [
@@ -658,7 +658,7 @@ EXPECTED;
         $this->assertTrue(true);
     }
 
-    public function dataMinimumWidth()
+    public static function dataMinimumWidth(): array
     {
         return [
             ['X'],
diff --git a/tests/framework/data/ActiveDataFilterTest.php b/tests/framework/data/ActiveDataFilterTest.php
index 57b96a6ab6..598fcca854 100644
--- a/tests/framework/data/ActiveDataFilterTest.php
+++ b/tests/framework/data/ActiveDataFilterTest.php
@@ -23,7 +23,7 @@ class ActiveDataFilterTest extends TestCase
 
     // Tests :
 
-    public function dataProviderBuild()
+    public static function dataProviderBuild(): array
     {
         return [
             [
diff --git a/tests/framework/data/DataFilterTest.php b/tests/framework/data/DataFilterTest.php
index c36e038c80..cd75719124 100644
--- a/tests/framework/data/DataFilterTest.php
+++ b/tests/framework/data/DataFilterTest.php
@@ -87,7 +87,7 @@ class DataFilterTest extends TestCase
      * Data provider for [[testValidate()]].
      * @return array test data.
      */
-    public function dataProviderValidate()
+    public static function dataProviderValidate(): array
     {
         return [
             [
@@ -295,7 +295,7 @@ class DataFilterTest extends TestCase
      * Data provider for [[testNormalize()]].
      * @return array test data.
      */
-    public function dataProviderNormalize()
+    public static function dataProviderNormalize(): array
     {
         return [
             [
diff --git a/tests/framework/data/PaginationTest.php b/tests/framework/data/PaginationTest.php
index bc19ce165e..5d64c4af35 100644
--- a/tests/framework/data/PaginationTest.php
+++ b/tests/framework/data/PaginationTest.php
@@ -33,7 +33,7 @@ class PaginationTest extends TestCase
      * Data provider for [[testCreateUrl()]].
      * @return array test data
      */
-    public function dataProviderCreateUrl()
+    public static function dataProviderCreateUrl(): array
     {
         return [
             [
@@ -116,7 +116,7 @@ class PaginationTest extends TestCase
         $this->assertEquals(999, $pagination->getPage());
     }
 
-    public function dataProviderPageCount()
+    public static function dataProviderPageCount(): array
     {
         return [
             [0, 0, 0],
@@ -153,7 +153,7 @@ class PaginationTest extends TestCase
         $this->assertEquals(0, (new Pagination())->getPage());
     }
 
-    public function dataProviderSetPage()
+    public static function dataProviderSetPage(): array
     {
         return [
             [null, false, 0, null],
@@ -188,7 +188,7 @@ class PaginationTest extends TestCase
         $this->assertEquals($page, $pagination->getPage());
     }
 
-    public function dataProviderGetPageSize()
+    public static function dataProviderGetPageSize(): array
     {
         return [
             [[1, 50], 20],
@@ -215,7 +215,7 @@ class PaginationTest extends TestCase
         $this->assertEquals($pageSize, $pagination->getPageSize());
     }
 
-    public function dataProviderSetPageSize()
+    public static function dataProviderSetPageSize(): array
     {
         return [
             [null, false, false, 20],
@@ -250,7 +250,7 @@ class PaginationTest extends TestCase
         $this->assertEquals($pageSize, $pagination->getPageSize());
     }
 
-    public function dataProviderGetOffset()
+    public static function dataProviderGetOffset(): array
     {
         return [
             [0, 0, 0],
@@ -277,7 +277,7 @@ class PaginationTest extends TestCase
         $this->assertEquals($offset, $pagination->getOffset());
     }
 
-    public function dataProviderGetLimit()
+    public static function dataProviderGetLimit(): array
     {
         return [
             [0, -1],
@@ -300,7 +300,7 @@ class PaginationTest extends TestCase
         $this->assertEquals($limit, $pagination->getLimit());
     }
 
-    public function dataProviderGetLinks()
+    public static function dataProviderGetLinks(): array
     {
         return [
             [0, 0, 0, '/index.php?r=list&page=1&per-page=0', null, null, null, null],
diff --git a/tests/framework/data/SortTest.php b/tests/framework/data/SortTest.php
index dc70179c42..78698cfac7 100644
--- a/tests/framework/data/SortTest.php
+++ b/tests/framework/data/SortTest.php
@@ -209,7 +209,7 @@ class SortTest extends TestCase
         $this->assertEquals('/index.php?r=site%2Findex&sort=age', $sort->createUrl('name'));
     }
 
-    public function providerForLinkWithParams()
+    public static function providerForLinkWithParams(): array
     {
         return [
             [true, null, '<a class="asc" href="/index.php?r=site%2Findex&amp;sort=-age%2C-name" data-sort="-age,-name">Age</a>'],
@@ -251,7 +251,7 @@ class SortTest extends TestCase
         $this->assertEquals($link, $sort->link('age'));
     }
 
-    public function providerForLinkWithParamsAndPassedButEmptySort()
+    public static function providerForLinkWithParamsAndPassedButEmptySort(): array
     {
         return [
             [null],
@@ -295,7 +295,7 @@ class SortTest extends TestCase
         );
     }
 
-    public function providerForLinkWithoutParams()
+    public static function providerForLinkWithoutParams(): array
     {
         return [
             [false, null, '<a href="/index.php?r=site%2Findex&amp;sort=age" data-sort="age">Age</a>'],
diff --git a/tests/framework/data/SqlDataProviderTest.php b/tests/framework/data/SqlDataProviderTest.php
index e997304e64..a338b724f4 100644
--- a/tests/framework/data/SqlDataProviderTest.php
+++ b/tests/framework/data/SqlDataProviderTest.php
@@ -48,7 +48,7 @@ class SqlDataProviderTest extends DatabaseTestCase
         $this->assertEquals(3, $dataProvider->getTotalCount());
     }
 
-    public function providerForOrderByColumn()
+    public static function providerForOrderByColumn(): array
     {
         return [
             'no marks' => ['name'],
diff --git a/tests/framework/di/ContainerTest.php b/tests/framework/di/ContainerTest.php
index 09d6fb963e..79f25594fc 100644
--- a/tests/framework/di/ContainerTest.php
+++ b/tests/framework/di/ContainerTest.php
@@ -592,7 +592,7 @@ class ContainerTest extends TestCase
         ]);
     }
 
-    public function dataNotInstantiableException()
+    public static function dataNotInstantiableException(): array
     {
         return [
             [Bar::class],
diff --git a/tests/framework/filters/AccessRuleTest.php b/tests/framework/filters/AccessRuleTest.php
index 5004dba606..a152ca17b5 100644
--- a/tests/framework/filters/AccessRuleTest.php
+++ b/tests/framework/filters/AccessRuleTest.php
@@ -218,7 +218,7 @@ class AccessRuleTest extends TestCase
      *           test user id
      *           expected match result (true, false, null)
      */
-    public function matchRoleProvider()
+    public static function matchRoleProvider(): array
     {
         return [
             ['create', true,  'user1',   [], true],
diff --git a/tests/framework/filters/HostControlTest.php b/tests/framework/filters/HostControlTest.php
index 9435f51e73..be34480ff8 100644
--- a/tests/framework/filters/HostControlTest.php
+++ b/tests/framework/filters/HostControlTest.php
@@ -33,7 +33,7 @@ class HostControlTest extends TestCase
     /**
      * @return array test data.
      */
-    public function hostInfoValidationDataProvider()
+    public static function hostInfoValidationDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/filters/PageCacheTest.php b/tests/framework/filters/PageCacheTest.php
index e81a28aed2..067d191a91 100644
--- a/tests/framework/filters/PageCacheTest.php
+++ b/tests/framework/filters/PageCacheTest.php
@@ -39,7 +39,7 @@ class PageCacheTest extends TestCase
         CacheTestCase::$microtime = null;
     }
 
-    public function cacheTestCaseProvider()
+    public static function cacheTestCaseProvider(): array
     {
         return [
             // Basic
diff --git a/tests/framework/filters/auth/AuthTest.php b/tests/framework/filters/auth/AuthTest.php
index 95e46d8c2e..a8fad5dc20 100644
--- a/tests/framework/filters/auth/AuthTest.php
+++ b/tests/framework/filters/auth/AuthTest.php
@@ -49,7 +49,7 @@ class AuthTest extends TestCase
         $this->mockWebApplication($appConfig);
     }
 
-    public function tokenProvider()
+    public static function tokenProvider(): array
     {
         return [
             ['token1', 'user1'],
@@ -136,7 +136,7 @@ class AuthTest extends TestCase
         $this->ensureFilterApplies($token, $login, $filter);
     }
 
-    public function authMethodProvider()
+    public static function authMethodProvider(): array
     {
         return [
             ['yii\filters\auth\CompositeAuth'],
diff --git a/tests/framework/filters/auth/BasicAuthTest.php b/tests/framework/filters/auth/BasicAuthTest.php
index efeba37e3e..99c786f956 100644
--- a/tests/framework/filters/auth/BasicAuthTest.php
+++ b/tests/framework/filters/auth/BasicAuthTest.php
@@ -122,7 +122,7 @@ class BasicAuthTest extends AuthTest
         $session->destroy();
     }
 
-    public function authMethodProvider()
+    public static function authMethodProvider(): array
     {
         return [
             ['yii\filters\auth\HttpBasicAuth'],
diff --git a/tests/framework/filters/auth/CompositeAuthTest.php b/tests/framework/filters/auth/CompositeAuthTest.php
index f5524ed48e..b6d0b979b8 100644
--- a/tests/framework/filters/auth/CompositeAuthTest.php
+++ b/tests/framework/filters/auth/CompositeAuthTest.php
@@ -178,7 +178,7 @@ class CompositeAuthTest extends TestCase
         $this->assertEquals('success', $controller->run('a'));
     }
 
-    public function compositeAuthDataProvider()
+    public static function compositeAuthDataProvider(): array
     {
         return [
             //base usage
diff --git a/tests/framework/grid/GridViewTest.php b/tests/framework/grid/GridViewTest.php
index e0261a2c87..81ae9dc010 100644
--- a/tests/framework/grid/GridViewTest.php
+++ b/tests/framework/grid/GridViewTest.php
@@ -44,7 +44,7 @@ class GridViewTest extends TestCase
     /**
      * @return array
      */
-    public function emptyDataProvider()
+    public static function emptyDataProvider(): array
     {
         return [
             [null, 'No results found.'],
diff --git a/tests/framework/grid/SerialColumnTest.php b/tests/framework/grid/SerialColumnTest.php
index 149264ccd6..2c5ac9ce05 100644
--- a/tests/framework/grid/SerialColumnTest.php
+++ b/tests/framework/grid/SerialColumnTest.php
@@ -10,6 +10,7 @@ declare(strict_types=1);
 
 namespace yiiunit\framework\grid;
 
+use yiiunit\TestCase;
 use Yii;
 use yii\data\ArrayDataProvider;
 use yii\data\Pagination;
@@ -19,7 +20,7 @@ use yii\grid\SerialColumn;
 /**
  * @group grid
  */
-class SerialColumnTest extends \yiiunit\TestCase
+class SerialColumnTest extends TestCase
 {
     /**
      * @dataProvider provideRenderDataCellData
diff --git a/tests/framework/helpers/ArrayHelperTest.php b/tests/framework/helpers/ArrayHelperTest.php
index 7aae8f965d..34cbf0b7c1 100644
--- a/tests/framework/helpers/ArrayHelperTest.php
+++ b/tests/framework/helpers/ArrayHelperTest.php
@@ -862,7 +862,7 @@ class ArrayHelperTest extends TestCase
         ArrayHelper::keyExists('a', $array, false);
     }
 
-    public function valueProvider()
+    public static function valueProvider(): array
     {
         return [
             ['name', 'test'],
@@ -995,7 +995,7 @@ class ArrayHelperTest extends TestCase
      * Data provider for [[testSetValue()]].
      * @return array test data
      */
-    public function dataProviderSetValue()
+    public static function dataProviderSetValue(): array
     {
         return [
             [
@@ -1571,7 +1571,7 @@ class ArrayHelperTest extends TestCase
      * Data provider for [[testRecursiveSort()]].
      * @return array test data
      */
-    public function dataProviderRecursiveSort()
+    public static function dataProviderRecursiveSort(): array
     {
         return [
             //Normal index array
diff --git a/tests/framework/helpers/BaseConsoleTest.php b/tests/framework/helpers/BaseConsoleTest.php
index 8ccaee812a..04d1a8ea15 100644
--- a/tests/framework/helpers/BaseConsoleTest.php
+++ b/tests/framework/helpers/BaseConsoleTest.php
@@ -71,7 +71,7 @@ class BaseConsoleTest extends TestCase
         $this->assertEquals($ansiExpected, $ansiActual);
     }
 
-    public function ansiColorizedSubstr_withColors_data()
+    public static function ansiColorizedSubstr_withColors_data(): array
     {
         return [
             ['%rFoo%gBar%n', 0, 3, '%rFoo%n'],
diff --git a/tests/framework/helpers/BaseUrlTest.php b/tests/framework/helpers/BaseUrlTest.php
index 28d1ca7358..48d7180340 100644
--- a/tests/framework/helpers/BaseUrlTest.php
+++ b/tests/framework/helpers/BaseUrlTest.php
@@ -28,7 +28,7 @@ class BaseUrlTest extends TestCase
         $this->assertEquals($expected, BaseUrl::ensureScheme($url, $scheme));
     }
 
-    public function ensureSchemeUrlProvider()
+    public static function ensureSchemeUrlProvider(): array
     {
         return [
             'relative url and https scheme will return input url' => [
@@ -69,7 +69,7 @@ class BaseUrlTest extends TestCase
         ];
     }
 
-    public function relativeTrueUrlProvider()
+    public static function relativeTrueUrlProvider(): array
     {
         return [
             'url url without protocol' => [
@@ -87,7 +87,7 @@ class BaseUrlTest extends TestCase
         ];
     }
 
-    public function relativeFalseUrlProvider()
+    public static function relativeFalseUrlProvider(): array
     {
         return [
             'url with https protocol' => [
diff --git a/tests/framework/helpers/ConsoleTest.php b/tests/framework/helpers/ConsoleTest.php
index 51698ab405..a2f3cbdf95 100644
--- a/tests/framework/helpers/ConsoleTest.php
+++ b/tests/framework/helpers/ConsoleTest.php
@@ -154,7 +154,7 @@ class ConsoleTest extends TestCase
         }
     }*/
 
-    public function ansiFormats()
+    public static function ansiFormats(): array
     {
         return [
             ['test', 'test'],
diff --git a/tests/framework/helpers/FileHelperTest.php b/tests/framework/helpers/FileHelperTest.php
index 7df3c08d05..785e22ae25 100644
--- a/tests/framework/helpers/FileHelperTest.php
+++ b/tests/framework/helpers/FileHelperTest.php
@@ -1266,7 +1266,7 @@ class FileHelperTest extends TestCase
         FileHelper::changeOwnership($useFile ? $file : null, $ownership, $mode);
     }
 
-    public function changeOwnershipInvalidArgumentsProvider()
+    public static function changeOwnershipInvalidArgumentsProvider(): array
     {
         return [
             [false, '123:123', null],
@@ -1288,7 +1288,7 @@ class FileHelperTest extends TestCase
         $this->assertEquals($extensions, FileHelper::getExtensionsByMimeType($mimeType));
     }
 
-    public function getExtensionsByMimeTypeProvider()
+    public static function getExtensionsByMimeTypeProvider(): array
     {
         return [
             [
@@ -1323,7 +1323,7 @@ class FileHelperTest extends TestCase
         $this->assertEquals($extension, FileHelper::getExtensionByMimeType($mimeType, $preferShort));
     }
 
-    public function getExtensionByMimeTypeProvider()
+    public static function getExtensionByMimeTypeProvider(): array
     {
         return [
             ['application/json', true, 'json'],
diff --git a/tests/framework/helpers/FormatConverterTest.php b/tests/framework/helpers/FormatConverterTest.php
index 728dbc239d..540af1f04f 100644
--- a/tests/framework/helpers/FormatConverterTest.php
+++ b/tests/framework/helpers/FormatConverterTest.php
@@ -73,7 +73,7 @@ class FormatConverterTest extends TestCase
         $this->assertEquals('\\o\\\'\\c\\l\\o\\c\\k', FormatConverter::convertDateIcuToPhp('\'o\'\'clock\''));
     }
 
-    public function providerForICU2PHPPatterns()
+    public static function providerForICU2PHPPatterns(): array
     {
         return [
             'two single quotes produce one' => ["''", "\\'"],
@@ -222,7 +222,7 @@ class FormatConverterTest extends TestCase
         );
     }
 
-    public function providerForICU2JUIPatterns()
+    public static function providerForICU2JUIPatterns(): array
     {
         return [
             'era designator like (Anno Domini)' => ['G', ''],
@@ -389,7 +389,7 @@ class FormatConverterTest extends TestCase
         $this->assertEquals($expected, $actual);
     }
 
-    public function providerForPHP2ICUPatterns()
+    public static function providerForPHP2ICUPatterns(): array
     {
         return [
             'single \' should be encoded as \'\', which internally should be encoded as \'\'\'\'' => ["'", "''"],
@@ -497,7 +497,7 @@ class FormatConverterTest extends TestCase
         $this->assertEquals('dd-mm-yy', FormatConverter::convertDatePhpToJui('d-m-Y'));
     }
 
-    public function providerForPHP2JUIPatterns()
+    public static function providerForPHP2JUIPatterns(): array
     {
         return [
             'Day of the month, 2 digits with leading zeros 	01 to 31' => ['d', 'dd'],
diff --git a/tests/framework/helpers/HtmlTest.php b/tests/framework/helpers/HtmlTest.php
index 0b1fe156a5..3d7fe06bef 100644
--- a/tests/framework/helpers/HtmlTest.php
+++ b/tests/framework/helpers/HtmlTest.php
@@ -205,7 +205,7 @@ class HtmlTest extends TestCase
      * Data provider for [[testBeginFormSimulateViaPost()]].
      * @return array test data
      */
-    public function dataProviderBeginFormSimulateViaPost()
+    public static function dataProviderBeginFormSimulateViaPost(): array
     {
         return [
           ['<form action="/foo" method="GET">', 'GET'],
@@ -255,7 +255,7 @@ class HtmlTest extends TestCase
     /**
      * @return array
      */
-    public function imgDataProvider()
+    public static function imgDataProvider(): array
     {
         return [
             [
@@ -426,7 +426,7 @@ class HtmlTest extends TestCase
     /**
      * @return array
      */
-    public function textareaDataProvider()
+    public static function textareaDataProvider(): array
     {
         return [
             [
@@ -618,7 +618,7 @@ EOD;
         );
     }
 
-    public function providerForNonStrictBooleanDropDownList()
+    public static function providerForNonStrictBooleanDropDownList(): array
     {
         return [
             [null, false, false, false],
@@ -653,7 +653,7 @@ HTML;
         );
     }
 
-    public function providerForStrictBooleanDropDownList()
+    public static function providerForStrictBooleanDropDownList(): array
     {
         return [
             [null, false, false, false],
@@ -1480,7 +1480,7 @@ EOD;
      * Data provider for [[testActiveTextInput()]].
      * @return array test data
      */
-    public function dataProviderActiveTextInput()
+    public static function dataProviderActiveTextInput(): array
     {
         return [
             [
@@ -1523,7 +1523,7 @@ EOD;
      * Data provider for [[testActiveTextInputMaxLength]].
      * @return array test data
      */
-    public function dataProviderActiveTextInputMaxLength()
+    public static function dataProviderActiveTextInputMaxLength(): array
     {
         return [
             [
@@ -1572,7 +1572,7 @@ EOD;
      * Data provider for [[testActivePasswordInput()]].
      * @return array test data
      */
-    public function dataProviderActivePasswordInput()
+    public static function dataProviderActivePasswordInput(): array
     {
         return [
             [
@@ -1615,7 +1615,7 @@ EOD;
      * Data provider for [[testActiveInput_TypeText]].
      * @return array test data
      */
-    public function dataProviderActiveInput_TypeText()
+    public static function dataProviderActiveInput_TypeText(): array
     {
         return [
             [
@@ -1654,7 +1654,7 @@ EOD;
         $this->assertEquals($expectedHtml, Html::activeInput('text', $model, 'name', $options));
     }
 
-    public function errorSummaryDataProvider()
+    public static function errorSummaryDataProvider(): array
     {
         return [
             [
@@ -1781,7 +1781,7 @@ EOD;
      * Data provider for [[testActiveTextArea()]].
      * @return array test data
      */
-    public function dataProviderActiveTextArea()
+    public static function dataProviderActiveTextArea(): array
     {
         return [
             [
@@ -1850,7 +1850,7 @@ EOD;
      * Data provider for [[testActiveRadio()]].
      * @return array test data
      */
-    public function dataProviderActiveRadio()
+    public static function dataProviderActiveRadio(): array
     {
         return [
             [
@@ -1894,7 +1894,7 @@ EOD;
      * Data provider for [[testActiveCheckbox()]].
      * @return array test data
      */
-    public function dataProviderActiveCheckbox()
+    public static function dataProviderActiveCheckbox(): array
     {
         return [
             [
@@ -1938,7 +1938,7 @@ EOD;
      * Data provider for [[testAttributeNameValidation()]].
      * @return array test data
      */
-    public function validAttributeNamesProvider()
+    public static function validAttributeNamesProvider(): array
     {
         $data = [
             ['asd]asdf.asdfa[asdfa', 'asdf.asdfa'],
@@ -1964,7 +1964,7 @@ EOD;
      * Data provider for [[testAttributeNameValidation()]].
      * @return array test data
      */
-    public function invalidAttributeNamesProvider()
+    public static function invalidAttributeNamesProvider(): array
     {
         return [
             ['. ..'],
@@ -2216,7 +2216,7 @@ HTML;
         $this->assertStringContainsString('placeholder="My placeholder: Name"', $html);
     }
 
-    public static function getInputIdDataProvider()
+    public static function getInputIdDataProvider(): array
     {
         return [
             [
@@ -2255,7 +2255,7 @@ HTML;
         ];
     }
 
-    public static function getInputIdByNameDataProvider()
+    public static function getInputIdByNameDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/helpers/IpHelperTest.php b/tests/framework/helpers/IpHelperTest.php
index 6cf57edf61..826f0caabb 100644
--- a/tests/framework/helpers/IpHelperTest.php
+++ b/tests/framework/helpers/IpHelperTest.php
@@ -24,7 +24,7 @@ class IpHelperTest extends TestCase
         $this->assertSame($expected, $version, $message);
     }
 
-    public function getIpVersionProvider()
+    public static function getIpVersionProvider(): array
     {
         return [
             ['192.168.0.1', IpHelper::IPV4],
@@ -44,7 +44,7 @@ class IpHelperTest extends TestCase
         $this->assertSame($expected, $expanded, $message);
     }
 
-    public function expandIpv6Provider()
+    public static function expandIpv6Provider(): array
     {
         return [
             ['fa01::1', 'fa01:0000:0000:0000:0000:0000:0000:0001'],
@@ -75,7 +75,7 @@ class IpHelperTest extends TestCase
         $this->assertSame($expected, $result, $message);
     }
 
-    public function ip2binProvider()
+    public static function ip2binProvider(): array
     {
         return [
             ['192.168.1.1', '11000000101010000000000100000001'],
@@ -99,7 +99,7 @@ class IpHelperTest extends TestCase
         $this->assertSame($expected, $result);
     }
 
-    public function inRangeProvider()
+    public static function inRangeProvider(): array
     {
         return [
             ['192.168.1.1/24', '192.168.0.0/23', true],
diff --git a/tests/framework/helpers/StringHelperTest.php b/tests/framework/helpers/StringHelperTest.php
index 3d4ae65a16..2aad94a7b8 100644
--- a/tests/framework/helpers/StringHelperTest.php
+++ b/tests/framework/helpers/StringHelperTest.php
@@ -167,7 +167,7 @@ class StringHelperTest extends TestCase
     /**
      * Rules that should work the same for case-sensitive and case-insensitive `startsWith()`.
      */
-    public function providerStartsWith()
+    public static function providerStartsWith(): array
     {
         return [
             // positive check
@@ -223,7 +223,7 @@ class StringHelperTest extends TestCase
     /**
      * Rules that should work the same for case-sensitive and case-insensitive `endsWith()`.
      */
-    public function providerEndsWith()
+    public static function providerEndsWith(): array
     {
         return [
             // positive check
@@ -307,7 +307,7 @@ class StringHelperTest extends TestCase
         $this->assertEquals($output, $decoded);
     }
 
-    public function base64UrlEncodedStringsProvider()
+    public static function base64UrlEncodedStringsProvider(): array
     {
         return [
             ['This is an encoded string', 'VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw=='],
@@ -321,7 +321,7 @@ class StringHelperTest extends TestCase
      * Data provider for [[testMatchWildcard()]]
      * @return array test data.
      */
-    public function dataProviderMatchWildcard()
+    public static function dataProviderMatchWildcard(): array
     {
         return [
             // *
@@ -404,7 +404,7 @@ class StringHelperTest extends TestCase
         $this->assertSame($expectedResult, StringHelper::matchWildcard($pattern, $string, $options));
     }
 
-    public function dataProviderMb_ucfirst()
+    public static function dataProviderMb_ucfirst(): array
     {
         return [
             ['foo', 'Foo'],
@@ -426,7 +426,7 @@ class StringHelperTest extends TestCase
         $this->assertSame($expectedResult, StringHelper::mb_ucfirst($string));
     }
 
-    public function dataProviderMb_ucwords()
+    public static function dataProviderMb_ucwords(): array
     {
         return [
             ['foo', 'Foo'],
@@ -465,7 +465,7 @@ class StringHelperTest extends TestCase
         $this->assertSame($expectedResult, StringHelper::dirname($string));
     }
 
-    public function dataProviderDirname()
+    public static function dataProviderDirname(): array
     {
         return [
             ['\\foo\\bar\\test', '\foo\bar'],
@@ -521,7 +521,7 @@ class StringHelperTest extends TestCase
         $this->assertSame($expectedResult, StringHelper::findBetween($string, $start, $end));
     }
 
-    public function dataProviderFindBetween()
+    public static function dataProviderFindBetween(): array
     {
         return [
             ['hello world hello', ' hello', ' world', null],  // end before start
diff --git a/tests/framework/helpers/VarDumperTest.php b/tests/framework/helpers/VarDumperTest.php
index 550455f993..10d9a55216 100644
--- a/tests/framework/helpers/VarDumperTest.php
+++ b/tests/framework/helpers/VarDumperTest.php
@@ -61,7 +61,7 @@ class VarDumperTest extends TestCase
      * Data provider for [[testExport()]].
      * @return array test data
      */
-    public function dataProviderExport()
+    public static function dataProviderExport(): array
     {
         // Regular :
 
diff --git a/tests/framework/i18n/FallbackMessageFormatterTest.php b/tests/framework/i18n/FallbackMessageFormatterTest.php
index dd4d8d4199..cf1f9297b3 100644
--- a/tests/framework/i18n/FallbackMessageFormatterTest.php
+++ b/tests/framework/i18n/FallbackMessageFormatterTest.php
@@ -30,7 +30,7 @@ class FallbackMessageFormatterTest extends TestCase
     public const SUBJECT = 'сабж';
     public const SUBJECT_VALUE = 'Answer to the Ultimate Question of Life, the Universe, and Everything';
 
-    public function patterns()
+    public static function patterns(): array
     {
         return [
             [
diff --git a/tests/framework/i18n/FormatterDateTest.php b/tests/framework/i18n/FormatterDateTest.php
index 7f4533eb02..459615d633 100644
--- a/tests/framework/i18n/FormatterDateTest.php
+++ b/tests/framework/i18n/FormatterDateTest.php
@@ -548,7 +548,7 @@ class FormatterDateTest extends TestCase
         $this->assertSame($this->formatter->nullDisplay, $this->formatter->asDuration(null));
     }
 
-    public function dateInputs()
+    public static function dateInputs(): array
     {
         return [
             ['2015-01-01 00:00:00', '2014-13-01 00:00:00'],
@@ -584,7 +584,7 @@ class FormatterDateTest extends TestCase
         $this->assertSame($expected, $this->formatter->asDatetime($value, 'yyyy-MM-dd HH:mm:ss'));
     }
 
-    public function provideTimezones()
+    public static function provideTimezones(): array
     {
         return [
             ['UTC'],
diff --git a/tests/framework/i18n/FormatterNumberTest.php b/tests/framework/i18n/FormatterNumberTest.php
index 6aec3faeae..00c65d62f4 100755
--- a/tests/framework/i18n/FormatterNumberTest.php
+++ b/tests/framework/i18n/FormatterNumberTest.php
@@ -46,7 +46,7 @@ class FormatterNumberTest extends TestCase
     /**
      * Provides some configuration that should not affect Integer formatter.
      */
-    public function differentConfigProvider()
+    public static function differentConfigProvider(): array
     {
         // make this test not break when intl is not installed
         if (!extension_loaded('intl')) {
@@ -824,7 +824,7 @@ class FormatterNumberTest extends TestCase
         $this->assertSame('1023 B', $this->formatter->asShortSize(1023));
     }
 
-    public function providerForDirectWrongTypeAttributes()
+    public static function providerForDirectWrongTypeAttributes(): array
     {
         return [
             'not-int key for int options' => [
@@ -870,7 +870,7 @@ class FormatterNumberTest extends TestCase
         $this->formatter->asInteger(1, $intOptions, $textOptions);
     }
 
-    public function providerForConfiguredWrongTypeAttributes()
+    public static function providerForConfiguredWrongTypeAttributes(): array
     {
         return [
             'not-int key for int options' => [
diff --git a/tests/framework/i18n/FormatterTest.php b/tests/framework/i18n/FormatterTest.php
index 9621a16581..a405e274a5 100644
--- a/tests/framework/i18n/FormatterTest.php
+++ b/tests/framework/i18n/FormatterTest.php
@@ -357,7 +357,7 @@ class FormatterTest extends TestCase
         $this->assertSame('1451602800', $this->formatter->asTimestamp($dateTime));
     }
 
-    public function lengthDataProvider()
+    public static function lengthDataProvider(): array
     {
         return [
             [
@@ -456,7 +456,7 @@ class FormatterTest extends TestCase
         $this->assertSame($expected, call_user_func_array([$this->formatter, 'asShortLength'], $arguments), 'Failed asserting that ' . $message);
     }
 
-    public function weightDataProvider()
+    public static function weightDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/i18n/I18NTest.php b/tests/framework/i18n/I18NTest.php
index 93cb751ea8..abfec405fb 100644
--- a/tests/framework/i18n/I18NTest.php
+++ b/tests/framework/i18n/I18NTest.php
@@ -230,7 +230,7 @@ class I18NTest extends TestCase
         Event::off(PhpMessageSource::class, PhpMessageSource::EVENT_MISSING_TRANSLATION);
     }
 
-    public function sourceLanguageDataProvider()
+    public static function sourceLanguageDataProvider(): array
     {
         return [
             ['en-GB'],
diff --git a/tests/framework/i18n/MessageFormatterTest.php b/tests/framework/i18n/MessageFormatterTest.php
index 78358aa707..59fa3993a2 100644
--- a/tests/framework/i18n/MessageFormatterTest.php
+++ b/tests/framework/i18n/MessageFormatterTest.php
@@ -30,7 +30,7 @@ class MessageFormatterTest extends TestCase
     public const SUBJECT = 'сабж';
     public const SUBJECT_VALUE = 'Answer to the Ultimate Question of Life, the Universe, and Everything';
 
-    public function patterns()
+    public static function patterns(): array
     {
         return [
             [
@@ -276,7 +276,7 @@ _MSG_
         ];
     }
 
-    public function parsePatterns()
+    public static function parsePatterns(): array
     {
         return [
             [
diff --git a/tests/framework/log/LoggerTest.php b/tests/framework/log/LoggerTest.php
index da77928138..5475a37fde 100644
--- a/tests/framework/log/LoggerTest.php
+++ b/tests/framework/log/LoggerTest.php
@@ -493,7 +493,7 @@ class LoggerTest extends TestCase
         $this->assertEquals([$fistCategory], $logger->getProfiling(['cat*'], ['category*']));
     }
 
-    public function providerForNonProfilingMessages()
+    public static function providerForNonProfilingMessages(): array
     {
         return [
             [Logger::LEVEL_ERROR],
diff --git a/tests/framework/log/TargetTest.php b/tests/framework/log/TargetTest.php
index 61e110ecbb..7728e9ec48 100644
--- a/tests/framework/log/TargetTest.php
+++ b/tests/framework/log/TargetTest.php
@@ -20,7 +20,7 @@ class TargetTest extends TestCase
 {
     public static $messages;
 
-    public function filters()
+    public static function filters(): array
     {
         return [
             [[], ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I']],
diff --git a/tests/framework/mail/BaseMailerTest.php b/tests/framework/mail/BaseMailerTest.php
index e3e364da33..f45da7e2db 100644
--- a/tests/framework/mail/BaseMailerTest.php
+++ b/tests/framework/mail/BaseMailerTest.php
@@ -216,7 +216,7 @@ class BaseMailerTest extends TestCase
         $this->assertEquals(strip_tags($htmlViewFileContent), $message->_textBody, 'Unable to render text by direct view!');
     }
 
-    public function htmlAndPlainProvider()
+    public static function htmlAndPlainProvider(): array
     {
         return [
             [
diff --git a/tests/framework/mutex/MutexTestTrait.php b/tests/framework/mutex/MutexTestTrait.php
index 0110115011..52d93a9de1 100644
--- a/tests/framework/mutex/MutexTestTrait.php
+++ b/tests/framework/mutex/MutexTestTrait.php
@@ -107,7 +107,7 @@ trait MutexTestTrait
         $this->assertFalse($mutexOne->isAcquired('non existing'));
     }
 
-    public static function mutexDataProvider()
+    public static function mutexDataProvider(): array
     {
         $utf = <<<'UTF'
 𝐘˛𝜄 ӏ𝕤 𝗮 𝔣𝖺𐑈𝝉, 𐑈ℯ𝔠ｕ𝒓𝗲, 𝝰𝞹𝒹 𝖊𝘧𝒇𝗶𝕔𝖎ⅇπτ Ｐ𝘏𝙿 𝖿г𝖺ｍ𝖾ｗσｒ𝐤.
diff --git a/tests/framework/rbac/DbManagerTestCase.php b/tests/framework/rbac/DbManagerTestCase.php
index 3a7b0d6e96..c43d5f9514 100644
--- a/tests/framework/rbac/DbManagerTestCase.php
+++ b/tests/framework/rbac/DbManagerTestCase.php
@@ -183,7 +183,7 @@ abstract class DbManagerTestCase extends ManagerTestCase
         $this->auth->assign($updatePost, $userId);
     }
 
-    public function emptyValuesProvider()
+    public static function emptyValuesProvider(): array
     {
         return [
             [0, 0, true],
diff --git a/tests/framework/rbac/ManagerTestCase.php b/tests/framework/rbac/ManagerTestCase.php
index b2199b8dc6..19c71bcfac 100644
--- a/tests/framework/rbac/ManagerTestCase.php
+++ b/tests/framework/rbac/ManagerTestCase.php
@@ -466,7 +466,7 @@ abstract class ManagerTestCase extends TestCase
         $this->assertNotEmpty($this->auth->getRoles());
     }
 
-    public function RBACItemsProvider()
+    public static function RBACItemsProvider(): array
     {
         return [
             [Item::TYPE_ROLE],
diff --git a/tests/framework/requirements/YiiRequirementCheckerTest.php b/tests/framework/requirements/YiiRequirementCheckerTest.php
index c611a01863..0338ac6bf8 100644
--- a/tests/framework/requirements/YiiRequirementCheckerTest.php
+++ b/tests/framework/requirements/YiiRequirementCheckerTest.php
@@ -149,7 +149,7 @@ class YiiRequirementCheckerTest extends TestCase
      * Data provider for [[testGetByteSize()]].
      * @return array
      */
-    public function dataProviderGetByteSize()
+    public static function dataProviderGetByteSize(): array
     {
         return [
             ['456', 456],
@@ -179,7 +179,7 @@ class YiiRequirementCheckerTest extends TestCase
      * Data provider for [[testCompareByteSize()]]
      * @return array
      */
-    public function dataProviderCompareByteSize()
+    public static function dataProviderCompareByteSize(): array
     {
         return [
             ['2M', '2K', '>', true],
diff --git a/tests/framework/rest/IndexActionTest.php b/tests/framework/rest/IndexActionTest.php
index f88c2dbb8b..e56f37cf82 100644
--- a/tests/framework/rest/IndexActionTest.php
+++ b/tests/framework/rest/IndexActionTest.php
@@ -129,7 +129,7 @@ class IndexActionTest extends TestCase
      * Data provider for [[testPrepareDataProviderWithPaginationAndSorting()]].
      * @return array test data
      */
-    public function dataProviderTestPrepareDataProviderWithPaginationAndSorting()
+    public static function dataProviderTestPrepareDataProviderWithPaginationAndSorting(): array
     {
         return [
             [ // Default config
diff --git a/tests/framework/rest/SerializerTest.php b/tests/framework/rest/SerializerTest.php
index 69a67dadcb..12dc546f91 100644
--- a/tests/framework/rest/SerializerTest.php
+++ b/tests/framework/rest/SerializerTest.php
@@ -285,7 +285,7 @@ class SerializerTest extends TestCase
         ], $serializer->serialize($model));
     }
 
-    public function dataProviderSerializeDataProvider()
+    public static function dataProviderSerializeDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/rest/UrlRuleTest.php b/tests/framework/rest/UrlRuleTest.php
index 5557a24660..c41d744c3f 100644
--- a/tests/framework/rest/UrlRuleTest.php
+++ b/tests/framework/rest/UrlRuleTest.php
@@ -224,7 +224,7 @@ class UrlRuleTest extends TestCase
      *   - first element is the route to create
      *   - second element is the expected URL
      */
-    public function createUrlDataProvider()
+    public static function createUrlDataProvider(): array
     {
         return [
             // with pluralize
@@ -415,7 +415,7 @@ class UrlRuleTest extends TestCase
      *   - second element is the expected URL
      *   - third element is the expected result of getCreateUrlStatus() method
      */
-    public static function getCreateUrlStatusProvider()
+    public static function getCreateUrlStatusProvider(): array
     {
         return [
             'single controller' => [
diff --git a/tests/framework/validators/DateValidatorTest.php b/tests/framework/validators/DateValidatorTest.php
index 78589e5bc1..57a567da83 100644
--- a/tests/framework/validators/DateValidatorTest.php
+++ b/tests/framework/validators/DateValidatorTest.php
@@ -236,7 +236,7 @@ class DateValidatorTest extends TestCase
         $this->assertFalse($model->hasErrors('attr_date'));
     }
 
-    public function provideTimezones()
+    public static function provideTimezones(): array
     {
         return [
             ['UTC'],
@@ -1074,7 +1074,7 @@ class DateValidatorTest extends TestCase
         $this->assertTrue($model->hasErrors('attr_date'));
     }
 
-    public function provideTestStrictDateFormatIntlFail()
+    public static function provideTestStrictDateFormatIntlFail(): array
     {
         return [
             ['yyyy-MM-dd', '13-Mar-19', true],
@@ -1111,7 +1111,7 @@ class DateValidatorTest extends TestCase
         $this->assertFalse($model->hasErrors('attr_date'));
     }
 
-    public function provideTestStrictDateFormatIntlPass()
+    public static function provideTestStrictDateFormatIntlPass(): array
     {
         return [
             ['yyyy-MM-dd', '0013-03-19', true],
@@ -1143,7 +1143,7 @@ class DateValidatorTest extends TestCase
         $this->assertTrue($model->hasErrors('attr_date'));
     }
 
-    public function provideTestStrictDateFormatPhpFail()
+    public static function provideTestStrictDateFormatPhpFail(): array
     {
         return [
             ['php:Y-m-d', '13-Mar-19', true],
@@ -1179,7 +1179,7 @@ class DateValidatorTest extends TestCase
         $this->assertFalse($model->hasErrors('attr_date'));
     }
 
-    public function provideTestStrictDateFormatPhpPass()
+    public static function provideTestStrictDateFormatPhpPass(): array
     {
         return [
             ['php:Y-m-d', '0013-03-19', true],
diff --git a/tests/framework/validators/EmailValidatorTest.php b/tests/framework/validators/EmailValidatorTest.php
index 13e0d6e4d4..0c805f5f4d 100644
--- a/tests/framework/validators/EmailValidatorTest.php
+++ b/tests/framework/validators/EmailValidatorTest.php
@@ -144,7 +144,7 @@ class EmailValidatorTest extends TestCase
         $this->assertFalse($model->hasErrors('attr_email'));
     }
 
-    public function malformedAddressesProvider()
+    public static function malformedAddressesProvider(): array
     {
         return [
             // this is the demo email used in the proof of concept of the exploit
diff --git a/tests/framework/validators/FileValidatorTest.php b/tests/framework/validators/FileValidatorTest.php
index 67ba98b659..c9753b0701 100644
--- a/tests/framework/validators/FileValidatorTest.php
+++ b/tests/framework/validators/FileValidatorTest.php
@@ -552,7 +552,7 @@ class FileValidatorTest extends TestCase
         $this->assertFalse($validator->validate($file));
     }
 
-    public function validMimeTypes()
+    public static function validMimeTypes(): array
     {
         $validMimeTypes = array_filter([
             ['test.svg', 'image/*', 'svg'],
@@ -575,7 +575,7 @@ class FileValidatorTest extends TestCase
         return $validMimeTypes;
     }
 
-    public function invalidMimeTypes()
+    public static function invalidMimeTypes(): array
     {
         return [
             ['test.txt', 'image/*', 'png, jpg'],
@@ -684,7 +684,7 @@ class FileValidatorTest extends TestCase
         $this->assertEquals($expected, $validator->validate($file), sprintf('Mime type validate fail: "%s" / "%s"', $mask, $fileMimeType));
     }
 
-    public function mimeTypeCaseInsensitive()
+    public static function mimeTypeCaseInsensitive(): array
     {
         return [
             ['Image/*', 'image/jp2', true],
diff --git a/tests/framework/validators/IpValidatorTest.php b/tests/framework/validators/IpValidatorTest.php
index 6276e62d1e..577c4d4d1e 100644
--- a/tests/framework/validators/IpValidatorTest.php
+++ b/tests/framework/validators/IpValidatorTest.php
@@ -31,7 +31,7 @@ class IpValidatorTest extends TestCase
         new IpValidator(['ipv4' => false, 'ipv6' => false]);
     }
 
-    public function provideRangesForSubstitution()
+    public static function provideRangesForSubstitution(): array
     {
         return [
             ['10.0.0.1', ['10.0.0.1']],
@@ -65,7 +65,7 @@ class IpValidatorTest extends TestCase
         $this->assertFalse($validator->validate('babe::cafe'));
     }
 
-    public function provideBadIps()
+    public static function provideBadIps(): array
     {
         return [['not.an.ip'], [['what an array', '??']], [123456], [true], [false], ['bad:forSure']];
     }
diff --git a/tests/framework/web/AssetBundleTest.php b/tests/framework/web/AssetBundleTest.php
index bd0e600bd4..f1e4bad481 100644
--- a/tests/framework/web/AssetBundleTest.php
+++ b/tests/framework/web/AssetBundleTest.php
@@ -263,7 +263,7 @@ EOF;
         $this->assertEqualsWithoutLE($expected, $view->renderFile('@yiiunit/data/views/rawlayout.php'));
     }
 
-    public function positionProvider()
+    public static function positionProvider(): array
     {
         return [
             [View::POS_HEAD, true],
@@ -414,7 +414,7 @@ EOF;
         $this->assertEqualsWithoutLE($expected, $view->renderFile('@yiiunit/data/views/rawlayout.php'));
     }
 
-    public function registerFileDataProvider()
+    public static function registerFileDataProvider(): array
     {
         return [
             // JS files registration
diff --git a/tests/framework/web/ErrorHandlerTest.php b/tests/framework/web/ErrorHandlerTest.php
index b82ab726d9..fa4cfbdee6 100644
--- a/tests/framework/web/ErrorHandlerTest.php
+++ b/tests/framework/web/ErrorHandlerTest.php
@@ -129,7 +129,7 @@ Exception: yii\web\NotFoundHttpException', $out);
         $this->assertStringContainsString('<a href="netbeans://open?file=' . $file . '&line=63">', $out);
     }
 
-    public function dataHtmlEncode()
+    public static function dataHtmlEncode(): array
     {
         return [
             [
diff --git a/tests/framework/web/JsonResponseFormatterTest.php b/tests/framework/web/JsonResponseFormatterTest.php
index 6f6229729f..4e4fd41856 100644
--- a/tests/framework/web/JsonResponseFormatterTest.php
+++ b/tests/framework/web/JsonResponseFormatterTest.php
@@ -29,7 +29,7 @@ class JsonResponseFormatterTest extends FormatterTest
         return new JsonResponseFormatter($configuration);
     }
 
-    public function formatScalarDataProvider()
+    public static function formatScalarDataProvider(): array
     {
         return [
             [1, 1],
@@ -39,7 +39,7 @@ class JsonResponseFormatterTest extends FormatterTest
         ];
     }
 
-    public function formatArrayDataProvider()
+    public static function formatArrayDataProvider(): array
     {
         return [
             // input, json, pretty json
@@ -76,7 +76,7 @@ class JsonResponseFormatterTest extends FormatterTest
         ];
     }
 
-    public function formatObjectDataProvider()
+    public static function formatObjectDataProvider(): array
     {
         return [
             [new Post(123, 'abc'), '{"id":123,"title":"abc"}'],
@@ -91,7 +91,7 @@ class JsonResponseFormatterTest extends FormatterTest
         ];
     }
 
-    public function formatTraversableObjectDataProvider()
+    public static function formatTraversableObjectDataProvider(): array
     {
         $postsStack = new SplStack();
         $postsStack->push(new Post(915, 'record1'));
@@ -102,14 +102,14 @@ class JsonResponseFormatterTest extends FormatterTest
         ];
     }
 
-    public function formatModelDataProvider()
+    public static function formatModelDataProvider(): array
     {
         return [
             [new ModelStub(['id' => 123, 'title' => 'abc', 'hidden' => 'hidden']), '{"id":123,"title":"abc"}'],
         ];
     }
 
-    public function contentTypeGenerationDataProvider()
+    public static function contentTypeGenerationDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/web/RequestTest.php b/tests/framework/web/RequestTest.php
index 851443cb17..bfc61cf69c 100644
--- a/tests/framework/web/RequestTest.php
+++ b/tests/framework/web/RequestTest.php
@@ -389,7 +389,7 @@ class RequestTest extends TestCase
         $this->assertEquals($_GET, ['id' => 63]);
     }
 
-    public function getHostInfoDataProvider()
+    public static function getHostInfoDataProvider(): array
     {
         return [
             // empty
@@ -593,7 +593,7 @@ class RequestTest extends TestCase
         $this->assertNull($request->getServerPort());
     }
 
-    public function isSecureServerDataProvider()
+    public static function isSecureServerDataProvider(): array
     {
         return [
             [['HTTPS' => 1], true],
@@ -721,7 +721,7 @@ class RequestTest extends TestCase
         $_SERVER = $original;
     }
 
-    public function isSecureServerWithoutTrustedHostDataProvider()
+    public static function isSecureServerWithoutTrustedHostDataProvider(): array
     {
         return [
             // RFC 7239 forwarded header is not enabled
@@ -760,7 +760,7 @@ class RequestTest extends TestCase
         $_SERVER = $original;
     }
 
-    public function getUserIPDataProvider()
+    public static function getUserIPDataProvider(): array
     {
         return [
             [
@@ -938,7 +938,7 @@ class RequestTest extends TestCase
         $_SERVER = $original;
     }
 
-    public function getUserIPWithoutTruestHostDataProvider()
+    public static function getUserIPWithoutTruestHostDataProvider(): array
     {
         return [
             // RFC 7239 forwarded is not enabled
@@ -980,7 +980,7 @@ class RequestTest extends TestCase
         $_SERVER = $original;
     }
 
-    public function getMethodDataProvider()
+    public static function getMethodDataProvider(): array
     {
         return [
             [
@@ -1014,7 +1014,7 @@ class RequestTest extends TestCase
         $_SERVER = $original;
     }
 
-    public function getIsAjaxDataProvider()
+    public static function getIsAjaxDataProvider(): array
     {
         return [
             [
@@ -1046,7 +1046,7 @@ class RequestTest extends TestCase
         $_SERVER = $original;
     }
 
-    public function getIsPjaxDataProvider()
+    public static function getIsPjaxDataProvider(): array
     {
         return [
             [
@@ -1090,7 +1090,7 @@ class RequestTest extends TestCase
         $this->assertNull($request->getOrigin());
     }
 
-    public function httpAuthorizationHeadersProvider()
+    public static function httpAuthorizationHeadersProvider(): array
     {
         return [
             ['not a base64 at all', [base64_decode('not a base64 at all'), null]],
@@ -1169,7 +1169,7 @@ class RequestTest extends TestCase
         $this->assertSame('default', $request->getBodyParam('unexisting', 'default'));
     }
 
-    public function getBodyParamsDataProvider()
+    public static function getBodyParamsDataProvider(): array
     {
         return [
             'json' => ['application/json', '{"foo":"bar","baz":1}', ['foo' => 'bar', 'baz' => 1]],
@@ -1193,7 +1193,7 @@ class RequestTest extends TestCase
         $this->assertSame($expected, $request->getBodyParams());
     }
 
-    public function trustedHostAndInjectedXForwardedForDataProvider()
+    public static function trustedHostAndInjectedXForwardedForDataProvider(): array
     {
         return [
             'emptyIPs' => ['1.1.1.1', '', null, ['10.10.10.10'], '1.1.1.1'],
@@ -1230,7 +1230,7 @@ class RequestTest extends TestCase
         $this->assertSame($expectedUserIp, $request->getUserIP());
     }
 
-    public function trustedHostAndXForwardedPortDataProvider()
+    public static function trustedHostAndXForwardedPortDataProvider(): array
     {
         return [
             'defaultPlain' => ['1.1.1.1', 80, null, null, 80],
@@ -1274,7 +1274,7 @@ class RequestTest extends TestCase
         $this->assertSame($expectedMethod, $request->getMethod());
     }
 
-    public function alreadyResolvedIpDataProvider()
+    public static function alreadyResolvedIpDataProvider(): array
     {
         return [
             'resolvedXForwardedFor' => [
@@ -1317,7 +1317,7 @@ class RequestTest extends TestCase
         $this->assertSame($expectedIsSecureConnection, $request->isSecureConnection, 'Secure connection fail!');
     }
 
-    public function parseForwardedHeaderDataProvider()
+    public static function parseForwardedHeaderDataProvider(): array
     {
         return [
             [
diff --git a/tests/framework/web/ResponseTest.php b/tests/framework/web/ResponseTest.php
index a9e695bbab..2d9f08037d 100644
--- a/tests/framework/web/ResponseTest.php
+++ b/tests/framework/web/ResponseTest.php
@@ -44,7 +44,7 @@ class ResponseTest extends TestCase
         $this->response = new Response();
     }
 
-    public function rightRanges()
+    public static function rightRanges(): array
     {
         // TODO test more cases for range requests and check for rfc compatibility
         // https://tools.ietf.org/html/rfc2616
@@ -83,7 +83,7 @@ class ResponseTest extends TestCase
         $this->assertEquals((string)$length, $headers->get('Content-Length'));
     }
 
-    public function wrongRanges()
+    public static function wrongRanges(): array
     {
         // TODO test more cases for range requests and check for rfc compatibility
         // https://tools.ietf.org/html/rfc2616
@@ -213,7 +213,7 @@ class ResponseTest extends TestCase
      * @link https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent/Firefox
      * @return array
      */
-    public function dataProviderAjaxRedirectInternetExplorer11()
+    public static function dataProviderAjaxRedirectInternetExplorer11(): array
     {
         return [
             ['Mozilla/5.0 (Android 4.4; Mobile; rv:41.0) Gecko/41.0 Firefox/41.0', [301 => 301, 302 => 302]], // Firefox
@@ -260,7 +260,7 @@ class ResponseTest extends TestCase
         static::assertEquals(200, $this->response->statusCode);
     }
 
-    public function dataProviderSetStatusCodeByException()
+    public static function dataProviderSetStatusCodeByException(): array
     {
         $data = [
             [
@@ -303,7 +303,7 @@ class ResponseTest extends TestCase
         return $data;
     }
 
-    public function formatDataProvider()
+    public static function formatDataProvider(): array
     {
         return [
             [Response::FORMAT_JSON, '{"value":1}'],
@@ -415,7 +415,7 @@ class ResponseTest extends TestCase
         }
     }
 
-    public function cookiesTestProvider()
+    public static function cookiesTestProvider(): array
     {
         $expireInt = time() + 3600;
         $expireString = date('D, d-M-Y H:i:s', $expireInt) . ' GMT';
diff --git a/tests/framework/web/UrlManagerCreateUrlTest.php b/tests/framework/web/UrlManagerCreateUrlTest.php
index 959c551558..a17c780d65 100644
--- a/tests/framework/web/UrlManagerCreateUrlTest.php
+++ b/tests/framework/web/UrlManagerCreateUrlTest.php
@@ -69,7 +69,7 @@ class UrlManagerCreateUrlTest extends TestCase
         return new UrlManager($config);
     }
 
-    public function variationsProvider()
+    public static function variationsProvider(): array
     {
         $baseUrlConfig = [
             'baseUrl' => '/test',
@@ -521,7 +521,7 @@ class UrlManagerCreateUrlTest extends TestCase
         $assertations($manager);
     }
 
-    public function absolutePatternsVariations()
+    public static function absolutePatternsVariations(): array
     {
         $baseUrlConfig = [
             'baseUrl' => '/test',
@@ -682,7 +682,7 @@ class UrlManagerCreateUrlTest extends TestCase
         $this->assertEquals($expected, $manager->createAbsoluteUrl($urlParams));
     }
 
-    public function multipleHostsRulesDataProvider()
+    public static function multipleHostsRulesDataProvider(): array
     {
         return [
             ['http://example.com'],
diff --git a/tests/framework/web/UrlManagerParseUrlTest.php b/tests/framework/web/UrlManagerParseUrlTest.php
index b4343c9dcd..9bdddeae0d 100644
--- a/tests/framework/web/UrlManagerParseUrlTest.php
+++ b/tests/framework/web/UrlManagerParseUrlTest.php
@@ -106,7 +106,7 @@ class UrlManagerParseUrlTest extends TestCase
         $this->assertFalse($manager->parseRequest($this->getRequest('module/site/index/')));
     }
 
-    public function suffixProvider()
+    public static function suffixProvider(): array
     {
         return [
             ['.html'],
diff --git a/tests/framework/web/UrlManagerTest.php b/tests/framework/web/UrlManagerTest.php
index 04726ea00e..c2506c8d7b 100644
--- a/tests/framework/web/UrlManagerTest.php
+++ b/tests/framework/web/UrlManagerTest.php
@@ -62,7 +62,7 @@ class UrlManagerTest extends TestCase
      * $showScriptName and $enableStrictParsing should have no effect in default format.
      * Passing these options ensures that.
      */
-    public function ignoredOptionsProvider()
+    public static function ignoredOptionsProvider(): array
     {
         return [
             [false, false],
@@ -215,7 +215,7 @@ class UrlManagerTest extends TestCase
     /**
      * @return array provides different names for UrlManager::$routeParam
      */
-    public function routeParamProvider()
+    public static function routeParamProvider(): array
     {
         return [
             ['r'], // default value
diff --git a/tests/framework/web/UrlRuleTest.php b/tests/framework/web/UrlRuleTest.php
index bd851c7fc0..21d348da07 100644
--- a/tests/framework/web/UrlRuleTest.php
+++ b/tests/framework/web/UrlRuleTest.php
@@ -1355,7 +1355,7 @@ class UrlRuleTest extends TestCase
      *   - third element is the expected URL
      *   - fourth element is the expected result of getCreateUrlStatus() method
      */
-    public static function getCreateUrlStatusProvider()
+    public static function getCreateUrlStatusProvider(): array
     {
         return [
             'route' => [
diff --git a/tests/framework/widgets/ActiveFieldTest.php b/tests/framework/widgets/ActiveFieldTest.php
index fc13bd7964..cb48d3df87 100644
--- a/tests/framework/widgets/ActiveFieldTest.php
+++ b/tests/framework/widgets/ActiveFieldTest.php
@@ -266,7 +266,7 @@ EOT;
         $this->assertEquals($expectedValue, $actualValue);
     }
 
-    public function hintDataProvider()
+    public static function hintDataProvider(): array
     {
         return [
             ['Hint Content', '<div class="hint-block">Hint Content</div>'],
diff --git a/tests/framework/widgets/ListViewTest.php b/tests/framework/widgets/ListViewTest.php
index 2e0420016e..6ae431a841 100644
--- a/tests/framework/widgets/ListViewTest.php
+++ b/tests/framework/widgets/ListViewTest.php
@@ -129,7 +129,7 @@ HTML,
         );
     }
 
-    public function itemViewOptions()
+    public static function itemViewOptions(): array
     {
         return [
             [
@@ -175,7 +175,7 @@ HTML,
         $this->assertEqualsWithoutLE($expected, $out);
     }
 
-    public function itemOptions()
+    public static function itemOptions(): array
     {
         return [
             [
@@ -348,7 +348,7 @@ HTML,
 </div>', $out);
     }
 
-    public function providerForSummary()
+    public static function providerForSummary(): array
     {
         return [
             'empty' => ['', '<div id="w0" class="list-view">