diff --git a/tests/Functional/Schema/AlterTableTest.php b/tests/Functional/Schema/AlterTableTest.php
new file mode 100644
index 00000000000..9dbf1554216
--- /dev/null
+++ b/tests/Functional/Schema/AlterTableTest.php
@@ -0,0 +1,218 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\DBAL\Tests\Functional\Schema;
+
+use Doctrine\DBAL\Platforms\AbstractMySQLPlatform;
+use Doctrine\DBAL\Platforms\DB2Platform;
+use Doctrine\DBAL\Platforms\OraclePlatform;
+use Doctrine\DBAL\Platforms\SQLitePlatform;
+use Doctrine\DBAL\Platforms\SQLServerPlatform;
+use Doctrine\DBAL\Schema\Table;
+use Doctrine\DBAL\Tests\FunctionalTestCase;
+use Doctrine\DBAL\Types\Types;
+
+class AlterTableTest extends FunctionalTestCase
+{
+    public function testAddPrimaryKeyOnExistingColumn(): void
+    {
+        if ($this->connection->getDatabasePlatform() instanceof SQLitePlatform) {
+            self::markTestSkipped(
+                'SQLite will automatically set up auto-increment behavior on the primary key column, which this test'
+                    . ' does not expect.',
+            );
+        }
+
+        $table = new Table('alter_pk');
+        $table->addColumn('id', Types::INTEGER);
+        $table->addColumn('val', Types::INTEGER);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->setPrimaryKey(['id']);
+        });
+    }
+
+    public function testAddPrimaryKeyOnNewAutoIncrementColumn(): void
+    {
+        if ($this->connection->getDatabasePlatform() instanceof DB2Platform) {
+            self::markTestSkipped(
+                'IBM DB2 LUW does not support adding identity columns to an existing table.',
+            );
+        }
+
+        $table = new Table('alter_pk');
+        $table->addColumn('val', Types::INTEGER);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->addColumn('id', Types::INTEGER, ['autoincrement' => true]);
+            $table->setPrimaryKey(['id']);
+        });
+    }
+
+    public function testAlterPrimaryKeyFromAutoincrementToNonAutoincrementColumn(): void
+    {
+        $platform = $this->connection->getDatabasePlatform();
+
+        if ($platform instanceof AbstractMySQLPlatform) {
+            self::markTestIncomplete(
+                'DBAL should not allow this migration on MySQL because an auto-increment column must be part of the'
+                    . ' primary key constraint.',
+            );
+        }
+
+        if ($platform instanceof SQLitePlatform) {
+            self::markTestSkipped(
+                'SQLite does not support auto-increment columns that are not part the primary key constraint',
+            );
+        }
+
+        $this->ensureDroppingPrimaryKeyConstraintIsSupported();
+
+        $table = new Table('alter_pk');
+        $table->addColumn('id1', Types::INTEGER, ['autoincrement' => true]);
+        $table->addColumn('id2', Types::INTEGER);
+        $table->setPrimaryKey(['id1']);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->dropPrimaryKey();
+            $table->setPrimaryKey(['id2']);
+        });
+    }
+
+    public function testDropPrimaryKeyWithAutoincrementColumn(): void
+    {
+        $platform = $this->connection->getDatabasePlatform();
+
+        if ($platform instanceof AbstractMySQLPlatform) {
+            self::markTestIncomplete(
+                'DBAL should not allow this migration on MySQL because an auto-increment column must be part of the'
+                    . ' primary key constraint.',
+            );
+        }
+
+        if ($platform instanceof SQLitePlatform) {
+            self::markTestSkipped(
+                'SQLite does not support auto-increment columns as part of composite primary key constraint',
+            );
+        }
+
+        $this->ensureDroppingPrimaryKeyConstraintIsSupported();
+
+        $table = new Table('alter_pk');
+        $table->addColumn('id1', Types::INTEGER, ['autoincrement' => true]);
+        $table->addColumn('id2', Types::INTEGER);
+        $table->setPrimaryKey(['id1', 'id2']);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->dropPrimaryKey();
+        });
+    }
+
+    public function testDropNonAutoincrementColumnFromCompositePrimaryKeyWithAutoincrementColumn(): void
+    {
+        if ($this->connection->getDatabasePlatform() instanceof AbstractMySQLPlatform) {
+            self::markTestIncomplete(
+                'DBAL does not restore the auto-increment attribute after dropping and adding the constraint,'
+                    . ' which is a bug.',
+            );
+        }
+
+        $this->ensureDroppingPrimaryKeyConstraintIsSupported();
+
+        $table = new Table('alter_pk');
+        $table->addColumn('id1', Types::INTEGER, ['autoincrement' => true]);
+        $table->addColumn('id2', Types::INTEGER);
+        $table->setPrimaryKey(['id1', 'id2']);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->dropPrimaryKey();
+            $table->setPrimaryKey(['id1']);
+        });
+    }
+
+    public function testAddNonAutoincrementColumnToPrimaryKeyWithAutoincrementColumn(): void
+    {
+        $platform = $this->connection->getDatabasePlatform();
+
+        if ($platform instanceof AbstractMySQLPlatform) {
+            self::markTestIncomplete(
+                'DBAL does not restore the auto-increment attribute after dropping and adding the constraint,'
+                    . ' which is a bug.',
+            );
+        }
+
+        if ($platform instanceof SQLitePlatform) {
+            self::markTestSkipped(
+                'SQLite does not support auto-increment columns as part of composite primary key constraint',
+            );
+        }
+
+        $this->ensureDroppingPrimaryKeyConstraintIsSupported();
+
+        $table = new Table('alter_pk');
+        $table->addColumn('id1', Types::INTEGER, ['autoincrement' => true]);
+        $table->addColumn('id2', Types::INTEGER);
+        $table->setPrimaryKey(['id1']);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->dropPrimaryKey();
+            $table->setPrimaryKey(['id1', 'id2']);
+        });
+    }
+
+    public function testAddNewColumnToPrimaryKey(): void
+    {
+        $this->ensureDroppingPrimaryKeyConstraintIsSupported();
+
+        $table = new Table('alter_pk');
+        $table->addColumn('id1', Types::INTEGER);
+        $table->setPrimaryKey(['id1']);
+
+        $this->testMigration($table, static function (Table $table): void {
+            $table->addColumn('id2', Types::INTEGER);
+            $table->dropPrimaryKey();
+            $table->setPrimaryKey(['id1', 'id2']);
+        });
+    }
+
+    private function ensureDroppingPrimaryKeyConstraintIsSupported(): void
+    {
+        $platform = $this->connection->getDatabasePlatform();
+
+        if (
+            ! ($platform instanceof DB2Platform)
+            && ! ($platform instanceof OraclePlatform)
+            && ! ($platform instanceof SQLServerPlatform)
+        ) {
+            return;
+        }
+
+        self::markTestIncomplete(
+            'Dropping primary key constraint on the currently used database platform is not implemented.',
+        );
+    }
+
+    private function testMigration(Table $oldTable, callable $migration): void
+    {
+        $this->dropAndCreateTable($oldTable);
+
+        $newTable = clone $oldTable;
+
+        $migration($newTable);
+
+        $schemaManager = $this->connection->createSchemaManager();
+
+        $diff = $schemaManager->createComparator()
+            ->compareTables($oldTable, $newTable);
+
+        $schemaManager->alterTable($diff);
+
+        $introspectedTable = $schemaManager->introspectTable($newTable->getName());
+
+        $diff = $schemaManager->createComparator()
+            ->compareTables($newTable, $introspectedTable);
+
+        self::assertTrue($diff->isEmpty());
+    }
+}
diff --git a/tests/Platforms/AbstractMySQLPlatformTestCase.php b/tests/Platforms/AbstractMySQLPlatformTestCase.php
index 266fa2c48b5..59c4aac1152 100644
--- a/tests/Platforms/AbstractMySQLPlatformTestCase.php
+++ b/tests/Platforms/AbstractMySQLPlatformTestCase.php
@@ -282,172 +282,6 @@ public function testBlobTypeDeclarationSQL(): void
         self::assertEquals('LONGBLOB', $this->platform->getBlobTypeDeclarationSQL([]));
     }
 
-    public function testAlterTableAddPrimaryKey(): void
-    {
-        $table = new Table('alter_table_add_pk');
-        $table->addColumn('id', Types::INTEGER);
-        $table->addColumn('foo', Types::INTEGER);
-        $table->addIndex(['id'], 'idx_id');
-
-        $diffTable = clone $table;
-
-        $diffTable->dropIndex('idx_id');
-        $diffTable->setPrimaryKey(['id']);
-
-        $diff = $this->createComparator()
-            ->compareTables($table, $diffTable);
-
-        self::assertEquals(
-            ['DROP INDEX idx_id ON alter_table_add_pk', 'ALTER TABLE alter_table_add_pk ADD PRIMARY KEY (id)'],
-            $this->platform->getAlterTableSQL($diff),
-        );
-    }
-
-    public function testAlterPrimaryKeyWithAutoincrementColumn(): void
-    {
-        $table = new Table('alter_primary_key');
-        $table->addColumn('id', Types::INTEGER, ['autoincrement' => true]);
-        $table->addColumn('foo', Types::INTEGER);
-        $table->setPrimaryKey(['id']);
-
-        $diffTable = clone $table;
-
-        $diffTable->dropPrimaryKey();
-        $diffTable->setPrimaryKey(['foo']);
-
-        $diff = $this->createComparator()
-            ->compareTables($table, $diffTable);
-
-        self::assertEquals(
-            [
-                'ALTER TABLE alter_primary_key MODIFY id INT NOT NULL',
-                'DROP INDEX `primary` ON alter_primary_key',
-                'ALTER TABLE alter_primary_key ADD PRIMARY KEY (foo)',
-            ],
-            $this->platform->getAlterTableSQL($diff),
-        );
-    }
-
-    public function testDropPrimaryKeyWithAutoincrementColumn(): void
-    {
-        $table = new Table('drop_primary_key');
-        $table->addColumn('id', Types::INTEGER, ['autoincrement' => true]);
-        $table->addColumn('foo', Types::INTEGER);
-        $table->addColumn('bar', Types::INTEGER);
-        $table->setPrimaryKey(['id', 'foo']);
-
-        $diffTable = clone $table;
-
-        $diffTable->dropPrimaryKey();
-
-        $diff = $this->createComparator()
-            ->compareTables($table, $diffTable);
-
-        self::assertEquals(
-            [
-                'ALTER TABLE drop_primary_key MODIFY id INT NOT NULL',
-                'DROP INDEX `primary` ON drop_primary_key',
-            ],
-            $this->platform->getAlterTableSQL($diff),
-        );
-    }
-
-    public function testDropNonAutoincrementColumnFromCompositePrimaryKeyWithAutoincrementColumn(): void
-    {
-        $table = new Table('tbl');
-        $table->addColumn('id', Types::INTEGER, ['autoincrement' => true]);
-        $table->addColumn('foo', Types::INTEGER);
-        $table->addColumn('bar', Types::INTEGER);
-        $table->setPrimaryKey(['id', 'foo']);
-
-        $diffTable = clone $table;
-
-        $diffTable->dropPrimaryKey();
-        $diffTable->setPrimaryKey(['id']);
-
-        $diff = $this->createComparator()
-            ->compareTables($table, $diffTable);
-
-        self::assertSame(
-            [
-                'ALTER TABLE tbl MODIFY id INT NOT NULL',
-                'DROP INDEX `primary` ON tbl',
-                'ALTER TABLE tbl ADD PRIMARY KEY (id)',
-            ],
-            $this->platform->getAlterTableSQL($diff),
-        );
-    }
-
-    public function testAddNonAutoincrementColumnToPrimaryKeyWithAutoincrementColumn(): void
-    {
-        $table = new Table('tbl');
-        $table->addColumn('id', Types::INTEGER, ['autoincrement' => true]);
-        $table->addColumn('foo', Types::INTEGER);
-        $table->addColumn('bar', Types::INTEGER);
-        $table->setPrimaryKey(['id']);
-
-        $diffTable = clone $table;
-
-        $diffTable->dropPrimaryKey();
-        $diffTable->setPrimaryKey(['id', 'foo']);
-
-        $diff = $this->createComparator()
-            ->compareTables($table, $diffTable);
-
-        self::assertSame(
-            [
-                'ALTER TABLE tbl MODIFY id INT NOT NULL',
-                'DROP INDEX `primary` ON tbl',
-                'ALTER TABLE tbl ADD PRIMARY KEY (id, foo)',
-            ],
-            $this->platform->getAlterTableSQL($diff),
-        );
-    }
-
-    public function testAddAutoIncrementPrimaryKey(): void
-    {
-        $keyTable = new Table('foo');
-        $keyTable->addColumn('id', Types::INTEGER, ['autoincrement' => true]);
-        $keyTable->addColumn('baz', Types::STRING, ['length' => 32]);
-        $keyTable->setPrimaryKey(['id']);
-
-        $oldTable = new Table('foo');
-        $oldTable->addColumn('baz', Types::STRING, ['length' => 32]);
-
-        $diff = $this->createComparator()
-            ->compareTables($oldTable, $keyTable);
-
-        $sql = $this->platform->getAlterTableSQL($diff);
-
-        self::assertEquals(['ALTER TABLE foo ADD id INT AUTO_INCREMENT NOT NULL, ADD PRIMARY KEY (id)'], $sql);
-    }
-
-    public function testAlterPrimaryKeyWithNewColumn(): void
-    {
-        $table = new Table('yolo');
-        $table->addColumn('pkc1', Types::INTEGER);
-        $table->addColumn('col_a', Types::INTEGER);
-        $table->setPrimaryKey(['pkc1']);
-
-        $diffTable = clone $table;
-
-        $diffTable->addColumn('pkc2', Types::INTEGER);
-        $diffTable->dropPrimaryKey();
-        $diffTable->setPrimaryKey(['pkc1', 'pkc2']);
-
-        $diff = $this->createComparator()
-            ->compareTables($table, $diffTable);
-
-        self::assertSame(
-            [
-                'DROP INDEX `primary` ON yolo',
-                'ALTER TABLE yolo ADD pkc2 INT NOT NULL',
-                'ALTER TABLE yolo ADD PRIMARY KEY (pkc1, pkc2)',
-            ],
-            $this->platform->getAlterTableSQL($diff),
-        );
-    }
-
     public function testInitializesDoctrineTypeMappings(): void
     {
         self::assertTrue($this->platform->hasDoctrineTypeMappingFor('binary'));