diff --git a/tests/framework/db/ActiveRecordTest.php b/tests/framework/db/ActiveRecordTest.php
index 6120ad34e9..232b87a9fe 100644
--- a/tests/framework/db/ActiveRecordTest.php
+++ b/tests/framework/db/ActiveRecordTest.php
@@ -813,12 +813,12 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         $this->assertEquals($eagerItemsCount, $lazyItemsCount);
     }
 
-    public function aliasMethodProvider()
+    public static function aliasMethodProvider(): array
     {
         return [
             ['explicit'], // c
-//            ['querysyntax'], // {{@customer}}
-//            ['applyAlias'], // $query->applyAlias('customer', 'id') // _aliases are currently not being populated
+            // ['querysyntax'], // {{@customer}}
+            // ['applyAlias'], // $query->applyAlias('customer', 'id') // _aliases are currently not being populated
             // later getRelationAlias() could be added
         ];
     }
@@ -1129,7 +1129,7 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         $this->assertInstanceOf('yiiunit\data\ar\Customer', $customerWithJoinIndexOrdered['user1']);
     }
 
-    public function tableNameProvider()
+    public static function tableNameProvider(): array
     {
         return [
             ['order', 'order_item'],
@@ -1895,7 +1895,7 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         $this->assertEquals($expectedAliases, $aliases);
     }
 
-    public function filterTableNamesFromAliasesProvider()
+    public static function filterTableNamesFromAliasesProvider(): array
     {
         return [
             'table name as string'         => ['customer', []],
@@ -1907,7 +1907,7 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         ];
     }
 
-    public function legalValuesForFindByCondition()
+    public static function legalValuesForFindByCondition(): array
     {
         return [
             [Customer::class, ['id' => 1]],
@@ -1938,7 +1938,7 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         $this->assertTrue(true);
     }
 
-    public function illegalValuesForFindByCondition()
+    public static function illegalValuesForFindByCondition(): array
     {
         return [
             [Customer::class, [['`id`=`id` and 1' => 1]]],
@@ -2133,7 +2133,7 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         }
     }
 
-    public function providerForUnlinkDelete()
+    public static function providerForUnlinkDelete(): array
     {
         return [
             'with delete' => [true, 0],
@@ -2180,7 +2180,7 @@ abstract class ActiveRecordTest extends DatabaseTestCase
         $this->assertNotNull($order->virtualCustomer);
     }
 
-    public function labelTestModelProvider()
+    public static function labelTestModelProvider(): array
     {
         $data = [];
 
diff --git a/tests/framework/db/ColumnSchemaBuilderTest.php b/tests/framework/db/ColumnSchemaBuilderTest.php
index 28b151cc22..059314baa8 100644
--- a/tests/framework/db/ColumnSchemaBuilderTest.php
+++ b/tests/framework/db/ColumnSchemaBuilderTest.php
@@ -27,7 +27,7 @@ abstract class ColumnSchemaBuilderTest extends DatabaseTestCase
     /**
      * @return array
      */
-    public function typesProvider()
+    public static function typesProvider(): array
     {
         return [
             ['integer NULL DEFAULT NULL', Schema::TYPE_INTEGER, null, [
diff --git a/tests/framework/db/CommandTest.php b/tests/framework/db/CommandTest.php
index 029117c56e..8fb0bdb417 100644
--- a/tests/framework/db/CommandTest.php
+++ b/tests/framework/db/CommandTest.php
@@ -245,7 +245,7 @@ SQL;
         $this->assertEquals('user5@example.com', $command->queryScalar());
     }
 
-    public function paramsNonWhereProvider()
+    public static function paramsNonWhereProvider(): array
     {
         return [
             ['SELECT SUBSTR(name, :len) FROM {{customer}} WHERE [[email]] = :email GROUP BY SUBSTR(name, :len)'],
@@ -380,7 +380,7 @@ SQL;
         setlocale(LC_NUMERIC, $locale);
     }
 
-    public function batchInsertSqlProvider()
+    public static function batchInsertSqlProvider(): array
     {
         return [
             'issue11242' => [
@@ -615,7 +615,7 @@ SQL;
      * Data provider for testInsertSelectFailed.
      * @return array
      */
-    public function invalidSelectColumns()
+    public static function invalidSelectColumns(): array
     {
         return [
             [[]],
@@ -805,7 +805,7 @@ SQL;
         $this->assertNotNull($db->getSchema()->getTableSchema($toTableName, true));
     }
 
-    public function upsertProvider()
+    public static function upsertProvider(): array
     {
         return [
             'regular values' => [
@@ -1343,7 +1343,7 @@ SQL;
      * Data provider for [[testGetRawSql()]].
      * @return array test data
      */
-    public function dataProviderGetRawSql()
+    public static function dataProviderGetRawSql(): array
     {
         return [
             [
diff --git a/tests/framework/db/SchemaTest.php b/tests/framework/db/SchemaTest.php
index 3547ab4e2c..ac722ae062 100644
--- a/tests/framework/db/SchemaTest.php
+++ b/tests/framework/db/SchemaTest.php
@@ -28,7 +28,7 @@ abstract class SchemaTest extends DatabaseTestCase
      */
     protected $expectedSchemas;
 
-    public function pdoAttributesProvider()
+    public static function pdoAttributesProvider(): array
     {
         return [
             [[PDO::ATTR_EMULATE_PREPARES => true]],
@@ -157,7 +157,7 @@ abstract class SchemaTest extends DatabaseTestCase
         $this->assertNotSame($noCacheTable, $refreshedTable);
     }
 
-    public function tableSchemaCachePrefixesProvider()
+    public static function tableSchemaCachePrefixesProvider(): array
     {
         $configs = [
             [
@@ -558,7 +558,7 @@ abstract class SchemaTest extends DatabaseTestCase
         $this->assertSame($expected, $columnSchema->dbTypecast($value));
     }
 
-    public function columnSchemaDbTypecastBooleanPhpTypeProvider()
+    public static function columnSchemaDbTypecastBooleanPhpTypeProvider(): array
     {
         return [
             [1, true],
@@ -646,7 +646,7 @@ abstract class SchemaTest extends DatabaseTestCase
         }
     }
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         return [
             '1: primary key' => ['T_constraints_1', 'primaryKey', new Constraint([
@@ -753,14 +753,14 @@ abstract class SchemaTest extends DatabaseTestCase
         ];
     }
 
-    public function lowercaseConstraintsProvider()
+    public static function lowercaseConstraintsProvider(): array
     {
-        return $this->constraintsProvider();
+        return static::constraintsProvider();
     }
 
-    public function uppercaseConstraintsProvider()
+    public static function uppercaseConstraintsProvider(): array
     {
-        return $this->constraintsProvider();
+        return static::constraintsProvider();
     }
 
     /**
diff --git a/tests/framework/db/cubrid/ColumnSchemaBuilderTest.php b/tests/framework/db/cubrid/ColumnSchemaBuilderTest.php
index 162a655a56..e9b0314c23 100644
--- a/tests/framework/db/cubrid/ColumnSchemaBuilderTest.php
+++ b/tests/framework/db/cubrid/ColumnSchemaBuilderTest.php
@@ -33,7 +33,7 @@ class ColumnSchemaBuilderTest extends \yiiunit\framework\db\ColumnSchemaBuilderT
     /**
      * @return array
      */
-    public function typesProvider()
+    public static function typesProvider(): array
     {
         return [
             ['integer UNSIGNED', Schema::TYPE_INTEGER, null, [
diff --git a/tests/framework/db/cubrid/CommandTest.php b/tests/framework/db/cubrid/CommandTest.php
index 29b2add60f..1087344aed 100644
--- a/tests/framework/db/cubrid/CommandTest.php
+++ b/tests/framework/db/cubrid/CommandTest.php
@@ -85,7 +85,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         $this->assertEquals('SELECT "id", "t"."name" FROM "customer" t', $command->sql);
     }
 
-    public function batchInsertSqlProvider()
+    public static function batchInsertSqlProvider(): array
     {
         $data = parent::batchInsertSqlProvider();
         $data['issue11242']['expected'] = 'INSERT INTO "type" ("int_col", "float_col", "char_col") VALUES (NULL, NULL, \'Kyiv {{city}}, Ukraine\')';
diff --git a/tests/framework/db/cubrid/SchemaTest.php b/tests/framework/db/cubrid/SchemaTest.php
index 23f9a374f9..2855a6733a 100644
--- a/tests/framework/db/cubrid/SchemaTest.php
+++ b/tests/framework/db/cubrid/SchemaTest.php
@@ -87,11 +87,11 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         return $columns;
     }
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         $result = parent::constraintsProvider();
         foreach ($result as $name => $constraints) {
-            $result[$name][2] = $this->convertPropertiesToAnycase($constraints[2]);
+            $result[$name][2] = static::convertPropertiesToAnycase($constraints[2]);
         }
         $result['1: check'][2] = false;
         unset($result['1: index'][2][0]);
@@ -108,27 +108,17 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         return $result;
     }
 
-    public function lowercaseConstraintsProvider(): void
-    {
-        $this->markTestSkipped('This test hangs on CUBRID.');
-    }
-
-    public function uppercaseConstraintsProvider(): void
-    {
-        $this->markTestSkipped('This test hangs on CUBRID.');
-    }
-
     /**
      * @param array|object|string $object
      * @param bool $isProperty
      * @return array|object|string
      */
-    private function convertPropertiesToAnycase($object, $isProperty = false)
+    private static function convertPropertiesToAnycase($object, $isProperty = false)
     {
         if (!$isProperty && \is_array($object)) {
             $result = [];
             foreach ($object as $name => $value) {
-                $result[] = $this->convertPropertiesToAnycase($value);
+                $result[] = static::convertPropertiesToAnycase($value);
             }
 
             return $result;
@@ -136,7 +126,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
 
         if (\is_object($object)) {
             foreach (array_keys((array) $object) as $name) {
-                $object->$name = $this->convertPropertiesToAnycase($object->$name, true);
+                $object->$name = static::convertPropertiesToAnycase($object->$name, true);
             }
         } elseif (\is_array($object) || \is_string($object)) {
             $object = new AnyCaseValue($object);
@@ -144,4 +134,26 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
 
         return $object;
     }
+
+    /**
+     * @dataProvider lowercaseConstraintsProvider
+     * @param string $tableName
+     * @param string $type
+     * @param mixed $expected
+     */
+    public function testTableSchemaConstraintsWithPdoLowercase($tableName, $type, $expected): void
+    {
+        $this->markTestSkipped('This test hangs on CUBRID.');
+    }
+
+    /**
+     * @dataProvider uppercaseConstraintsProvider
+     * @param string $tableName
+     * @param string $type
+     * @param mixed $expected
+     */
+    public function testTableSchemaConstraintsWithPdoUppercase($tableName, $type, $expected): void
+    {
+        $this->markTestSkipped('This test hangs on CUBRID.');
+    }
 }
diff --git a/tests/framework/db/mssql/CommandTest.php b/tests/framework/db/mssql/CommandTest.php
index f161c9c001..9198054fa7 100644
--- a/tests/framework/db/mssql/CommandTest.php
+++ b/tests/framework/db/mssql/CommandTest.php
@@ -90,7 +90,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         $this->assertEquals('user5@example.com', $command->queryScalar());
     }
 
-    public function paramsNonWhereProvider()
+    public static function paramsNonWhereProvider(): array
     {
         return[
             ['SELECT SUBSTRING(name, :len, 6) AS name FROM {{customer}} WHERE [[email]] = :email GROUP BY name'],
@@ -122,7 +122,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         $this->assertEmpty($schema->getTableDefaultValues($tableName, true));
     }
 
-    public function batchInsertSqlProvider()
+    public static function batchInsertSqlProvider(): array
     {
         $data = parent::batchInsertSqlProvider();
         $data['issue11242']['expected'] = 'INSERT INTO [type] ([int_col], [float_col], [char_col]) VALUES (NULL, NULL, \'Kyiv {{city}}, Ukraine\')';
diff --git a/tests/framework/db/mssql/SchemaTest.php b/tests/framework/db/mssql/SchemaTest.php
index 0414abaad5..8c409f9944 100644
--- a/tests/framework/db/mssql/SchemaTest.php
+++ b/tests/framework/db/mssql/SchemaTest.php
@@ -25,7 +25,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         'dbo',
     ];
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         $result = parent::constraintsProvider();
         $result['1: check'][2][0]->expression = '([C_check]<>\'\')';
@@ -100,7 +100,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         $this->assertEquals($expectedName, $quotedName);
     }
 
-    public function quoteTableNameDataProvider()
+    public static function quoteTableNameDataProvider(): array
     {
         return [
             ['test', '[test]'],
@@ -127,7 +127,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         $this->assertEquals($expectedName, $tableSchema->name);
     }
 
-    public function getTableSchemaDataProvider()
+    public static function getTableSchemaDataProvider(): array
     {
         return [
             ['[dbo].[profile]', 'profile'],
diff --git a/tests/framework/db/mysql/ColumnSchemaBuilderTest.php b/tests/framework/db/mysql/ColumnSchemaBuilderTest.php
index d8b99e2fff..b6e31fe57c 100644
--- a/tests/framework/db/mysql/ColumnSchemaBuilderTest.php
+++ b/tests/framework/db/mysql/ColumnSchemaBuilderTest.php
@@ -33,7 +33,7 @@ class ColumnSchemaBuilderTest extends \yiiunit\framework\db\ColumnSchemaBuilderT
     /**
      * @return array
      */
-    public function typesProvider()
+    public static function typesProvider(): array
     {
         return [
             ['integer UNSIGNED', Schema::TYPE_INTEGER, null, [
diff --git a/tests/framework/db/mysql/SchemaTest.php b/tests/framework/db/mysql/SchemaTest.php
index 99352eb9e1..e6c178dad5 100644
--- a/tests/framework/db/mysql/SchemaTest.php
+++ b/tests/framework/db/mysql/SchemaTest.php
@@ -76,7 +76,7 @@ SQL;
         $this->markTestSkipped('Schemas are not supported in MySQL.');
     }
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         $result = parent::constraintsProvider();
 
diff --git a/tests/framework/db/oci/ColumnSchemaBuilderTest.php b/tests/framework/db/oci/ColumnSchemaBuilderTest.php
index 2fdef80b09..2a673fba7d 100644
--- a/tests/framework/db/oci/ColumnSchemaBuilderTest.php
+++ b/tests/framework/db/oci/ColumnSchemaBuilderTest.php
@@ -33,7 +33,7 @@ class ColumnSchemaBuilderTest extends \yiiunit\framework\db\ColumnSchemaBuilderT
     /**
      * @return array
      */
-    public function typesProvider()
+    public static function typesProvider(): array
     {
         return [
             ['integer UNSIGNED', Schema::TYPE_INTEGER, null, [
diff --git a/tests/framework/db/oci/CommandTest.php b/tests/framework/db/oci/CommandTest.php
index d61e79ef24..4d881f9348 100644
--- a/tests/framework/db/oci/CommandTest.php
+++ b/tests/framework/db/oci/CommandTest.php
@@ -42,7 +42,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         $this->assertSame('3', $db->getSchema()->getLastInsertID('profile_SEQ'));
     }
 
-    public function batchInsertSqlProvider()
+    public static function batchInsertSqlProvider(): array
     {
         $data = parent::batchInsertSqlProvider();
         $data['issue11242']['expected'] = 'INSERT ALL  INTO "type" ("int_col", "float_col", "char_col") ' .
@@ -161,7 +161,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         }, 10);
     }
 
-    public function paramsNonWhereProvider()
+    public static function paramsNonWhereProvider(): array
     {
         return [
             ['SELECT SUBSTR([[name]], :len) FROM {{customer}} WHERE [[email]] = :email GROUP BY SUBSTR([[name]], :len)'],
diff --git a/tests/framework/db/oci/SchemaTest.php b/tests/framework/db/oci/SchemaTest.php
index cea1d2e478..d8b41cdb83 100644
--- a/tests/framework/db/oci/SchemaTest.php
+++ b/tests/framework/db/oci/SchemaTest.php
@@ -110,7 +110,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         $this->assertFalse($table->columns['id']->autoIncrement);
     }
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         $result = parent::constraintsProvider();
         $result['1: check'][2][0]->expression = '"C_check" <> \'\'';
diff --git a/tests/framework/db/pgsql/ActiveRecordTest.php b/tests/framework/db/pgsql/ActiveRecordTest.php
index 126489e08c..545b680816 100644
--- a/tests/framework/db/pgsql/ActiveRecordTest.php
+++ b/tests/framework/db/pgsql/ActiveRecordTest.php
@@ -215,7 +215,7 @@ class ActiveRecordTest extends \yiiunit\framework\db\ActiveRecordTest
         $this->assertSame(1, $type->update(), 'The record got updated');
     }
 
-    public function arrayValuesProvider()
+    public static function arrayValuesProvider(): array
     {
         return [
             'simple arrays values' => [[
diff --git a/tests/framework/db/pgsql/ArrayParserTest.php b/tests/framework/db/pgsql/ArrayParserTest.php
index 6aa8d6ba3d..3f23a3530f 100644
--- a/tests/framework/db/pgsql/ArrayParserTest.php
+++ b/tests/framework/db/pgsql/ArrayParserTest.php
@@ -19,7 +19,7 @@ class ArrayParserTest extends TestCase
         $this->arrayParser = new ArrayParser();
     }
 
-    public function convertProvider()
+    public static function convertProvider(): array
     {
         return [
             ['{}', []],
diff --git a/tests/framework/db/pgsql/CommandTest.php b/tests/framework/db/pgsql/CommandTest.php
index 7e28dcfd30..9bad5028aa 100644
--- a/tests/framework/db/pgsql/CommandTest.php
+++ b/tests/framework/db/pgsql/CommandTest.php
@@ -80,7 +80,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         $this->assertSame('3', $db->getSchema()->getLastInsertID('schema1.profile_id_seq'));
     }
 
-    public function dataProviderGetRawSql()
+    public static function dataProviderGetRawSql(): array
     {
         return array_merge(parent::dataProviderGetRawSql(), [
             [
@@ -117,7 +117,7 @@ class CommandTest extends \yiiunit\framework\db\CommandTest
         $this->assertEquals(1, $command->execute());
     }
 
-    public function batchInsertSqlProvider()
+    public static function batchInsertSqlProvider(): array
     {
         $data = parent::batchInsertSqlProvider();
         $data['issue11242']['expected'] = 'INSERT INTO "type" ("int_col", "float_col", "char_col") VALUES (NULL, NULL, \'Kyiv {{city}}, Ukraine\')';
diff --git a/tests/framework/db/pgsql/SchemaTest.php b/tests/framework/db/pgsql/SchemaTest.php
index 1fe2655cd2..0148cee033 100644
--- a/tests/framework/db/pgsql/SchemaTest.php
+++ b/tests/framework/db/pgsql/SchemaTest.php
@@ -261,7 +261,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         $this->assertCount(3, $schema->getSchemaNames());
     }
 
-    public function bigintValueProvider()
+    public static function bigintValueProvider(): array
     {
         return [
             [8817806877],
@@ -402,7 +402,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         $this->assertEquals(new Expression('timezone(\'UTC\'::text, \'1970-01-01 00:00:00+00\'::timestamp with time zone)'), $tableSchema->getColumn('timestamp')->defaultValue);
     }
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         $result = parent::constraintsProvider();
         $result['1: check'][2][0]->expression = 'CHECK ((("C_check")::text <> \'\'::text))';
diff --git a/tests/framework/db/sqlite/ColumnSchemaBuilderTest.php b/tests/framework/db/sqlite/ColumnSchemaBuilderTest.php
index 8373af0ae2..6a0c05c18d 100644
--- a/tests/framework/db/sqlite/ColumnSchemaBuilderTest.php
+++ b/tests/framework/db/sqlite/ColumnSchemaBuilderTest.php
@@ -33,7 +33,7 @@ class ColumnSchemaBuilderTest extends \yiiunit\framework\db\ColumnSchemaBuilderT
     /**
      * @return array
      */
-    public function typesProvider()
+    public static function typesProvider(): array
     {
         return [
             ['integer UNSIGNED', Schema::TYPE_INTEGER, null, [
diff --git a/tests/framework/db/sqlite/CommandTest.php b/tests/framework/db/sqlite/CommandTest.php
index 20ebbf789f..2d697b6b07 100644
--- a/tests/framework/db/sqlite/CommandTest.php
+++ b/tests/framework/db/sqlite/CommandTest.php
@@ -105,7 +105,7 @@ SQL;
         ])->queryAll());
     }
 
-    public function batchInsertSqlProvider()
+    public static function batchInsertSqlProvider(): array
     {
         $parent = parent::batchInsertSqlProvider();
         unset($parent['wrongBehavior']); // Produces SQL syntax error: General error: 1 near ".": syntax error
diff --git a/tests/framework/db/sqlite/SchemaTest.php b/tests/framework/db/sqlite/SchemaTest.php
index 2786e6c110..757add20ab 100644
--- a/tests/framework/db/sqlite/SchemaTest.php
+++ b/tests/framework/db/sqlite/SchemaTest.php
@@ -58,7 +58,7 @@ class SchemaTest extends \yiiunit\framework\db\SchemaTest
         $this->assertEquals('item_id', $table->foreignKeys[0]['item_id']);
     }
 
-    public function constraintsProvider()
+    public static function constraintsProvider(): array
     {
         $result = parent::constraintsProvider();
         $result['1: primary key'][2]->name = null;
diff --git a/tests/framework/db/sqlite/SqlTokenizerTest.php b/tests/framework/db/sqlite/SqlTokenizerTest.php
index f1acd34ef8..62dc506612 100644
--- a/tests/framework/db/sqlite/SqlTokenizerTest.php
+++ b/tests/framework/db/sqlite/SqlTokenizerTest.php
@@ -18,7 +18,7 @@ use yiiunit\TestCase;
  */
 class SqlTokenizerTest extends TestCase
 {
-    public function sqlProvider()
+    public static function sqlProvider(): array
     {
         return [
             'complex' => [