class DriverSpecificSchemaTestBase

abstract class DriverSpecificSchemaTestBase extends DriverSpecificKernelTestBase {
  use SchemaIntrospectionTestTrait;
  
  /**
   * Database schema instance.
   */
  protected Schema $schema;
  
  /**
   * A global counter for table and field creation.
   */
  protected int $counter = 0;
  
  /**
   * Connection to the database.
   */
  protected Connection $connection;
  
  /**
   * {@inheritdoc}
   */
  protected function setUp() : void {
    parent::setUp();
    $this->schema = $this->connection
      ->schema();
  }
  
  /**
   * Checks that a table or column comment matches a given description.
   *
   * @param string|false $description
   *   The asserted description. Use FALSE to assert there is no description.
   * @param string $table
   *   The table to test.
   * @param string|null $column
   *   Optional column to test.
   */
  abstract public function checkSchemaComment(string|false $description, string $table, ?string $column = NULL) : void;
  
  /**
   * Tests inserting data into an existing table.
   *
   * @param string $table
   *   The database table to insert data into.
   *
   * @return bool
   *   TRUE if the insert succeeded, FALSE otherwise.
   */
  public function tryInsert(string $table = 'test_table') : bool {
    try {
      $this->connection
        ->insert($table)
        ->fields([
        'id' => mt_rand(10, 20),
      ])
        ->execute();
      return TRUE;
    } catch (\Exception) {
      return FALSE;
    }
  }
  
  /**
   * Tries to insert a negative value into columns defined as unsigned.
   *
   * @param string $table_name
   *   The table to insert.
   * @param string $column_name
   *   The column to insert.
   *
   * @return bool
   *   TRUE if the insert succeeded, FALSE otherwise.
   */
  public function tryUnsignedInsert(string $table_name, string $column_name) : bool {
    try {
      $this->connection
        ->insert($table_name)
        ->fields([
        $column_name => -1,
      ])
        ->execute();
      return TRUE;
    } catch (\Exception) {
      return FALSE;
    }
  }
  
  /**
   * Tries to insert a value that throws an IntegrityConstraintViolationException.
   *
   * @param string $tableName
   *   The table to insert.
   */
  protected function tryInsertExpectsIntegrityConstraintViolationException(string $tableName) : void {
    try {
      $this->connection
        ->insert($tableName)
        ->fields([
        'test_field_string' => 'test',
      ])
        ->execute();
      $this->fail('Expected IntegrityConstraintViolationException not thrown');
    } catch (IntegrityConstraintViolationException) {
      // Do nothing, it's the expected behavior.
    }
  }
  
  /**
   * Asserts that fields have the correct collation, if supported.
   */
  protected function assertCollation() : void {
    // Driver specific tests should implement this when appropriate.
  }
  
  /**
   * Check that the ID sequence gets renamed when the table is renamed.
   *
   * @param string $tableName
   *   The table to rename.
   */
  protected function checkSequenceRenaming(string $tableName) : void {
    // Driver specific tests should implement this when appropriate.
  }
  
  /**
   * Tests database interactions.
   */
  public function testSchema() : void {
    // Try creating a table.
    $table_specification = [
      'description' => 'Schema table description may contain "quotes" and could be long—very long indeed.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'default' => NULL,
        ],
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
          'description' => 'Schema table description may contain "quotes" and could be long—very long indeed. There could be "multiple quoted regions".',
        ],
        'test_field_string' => [
          'type' => 'varchar',
          'length' => 20,
          'not null' => TRUE,
          'default' => "'\"funky default'\"",
          'description' => 'Schema column description for string.',
        ],
        'test_field_string_ascii' => [
          'type' => 'varchar_ascii',
          'length' => 255,
          'description' => 'Schema column description for ASCII string.',
        ],
      ],
    ];
    $this->schema
      ->createTable('test_table', $table_specification);
    // Assert that the table exists.
    $this->assertTrue($this->schema
      ->tableExists('test_table'), 'The table exists.');
    // Assert that the table comment has been set.
    $this->checkSchemaComment($table_specification['description'], 'test_table');
    // Assert that the column comment has been set.
    $this->checkSchemaComment($table_specification['fields']['test_field']['description'], 'test_table', 'test_field');
    // Make sure that fields have the correct collation, if supported.
    $this->assertCollation();
    // An insert without a value for the column 'test_table' should fail.
    $this->assertFalse($this->tryInsert(), 'Insert without a default failed.');
    // Add a default value to the column.
    $this->schema
      ->changeField('test_table', 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
      'default' => 0,
    ]);
    // The insert should now succeed.
    $this->assertTrue($this->tryInsert(), 'Insert with a default succeeded.');
    // Remove the default.
    $this->schema
      ->changeField('test_table', 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
    ]);
    // The insert should fail again.
    $this->assertFalse($this->tryInsert(), 'Insert without a default failed.');
    // Test for fake index and test for the boolean result of indexExists().
    $index_exists = $this->schema
      ->indexExists('test_table', 'test_field');
    $this->assertFalse($index_exists, 'Fake index does not exist');
    // Add index.
    $this->schema
      ->addIndex('test_table', 'test_field', [
      'test_field',
    ], $table_specification);
    // Test for created index and test for the boolean result of indexExists().
    $index_exists = $this->schema
      ->indexExists('test_table', 'test_field');
    $this->assertTrue($index_exists, 'Index created.');
    // Rename the table.
    $this->assertNull($this->schema
      ->renameTable('test_table', 'test_table2'));
    // Index should be renamed.
    $index_exists = $this->schema
      ->indexExists('test_table2', 'test_field');
    $this->assertTrue($index_exists, 'Index was renamed.');
    // We need the default so that we can insert after the rename.
    $this->schema
      ->changeField('test_table2', 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
      'default' => 0,
    ]);
    $this->assertFalse($this->tryInsert(), 'Insert into the old table failed.');
    $this->assertTrue($this->tryInsert('test_table2'), 'Insert into the new table succeeded.');
    // We should have successfully inserted exactly two rows.
    $count = $this->connection
      ->query('SELECT COUNT(*) FROM {test_table2}')
      ->fetchField();
    $this->assertEquals(2, $count, 'Two fields were successfully inserted.');
    // Try to drop the table.
    $this->schema
      ->dropTable('test_table2');
    $this->assertFalse($this->schema
      ->tableExists('test_table2'), 'The dropped table does not exist.');
    // Recreate the table.
    $this->schema
      ->createTable('test_table', $table_specification);
    $this->schema
      ->changeField('test_table', 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
      'default' => 0,
    ]);
    $this->schema
      ->addField('test_table', 'test_serial', [
      'type' => 'int',
      'not null' => TRUE,
      'default' => 0,
      'description' => 'Added column description.',
    ]);
    // Assert that the column comment has been set.
    $this->checkSchemaComment('Added column description.', 'test_table', 'test_serial');
    // Change the new field to a serial column.
    $this->schema
      ->changeField('test_table', 'test_serial', 'test_serial', [
      'type' => 'serial',
      'not null' => TRUE,
      'description' => 'Changed column description.',
    ], [
      'primary key' => [
        'test_serial',
      ],
    ]);
    // Assert that the column comment has been set.
    $this->checkSchemaComment('Changed column description.', 'test_table', 'test_serial');
    $this->assertTrue($this->tryInsert(), 'Insert with a serial succeeded.');
    $max1 = $this->connection
      ->query('SELECT MAX([test_serial]) FROM {test_table}')
      ->fetchField();
    $this->assertTrue($this->tryInsert(), 'Insert with a serial succeeded.');
    $max2 = $this->connection
      ->query('SELECT MAX([test_serial]) FROM {test_table}')
      ->fetchField();
    $this->assertTrue($max2 > $max1, 'The serial is monotone.');
    $count = $this->connection
      ->query('SELECT COUNT(*) FROM {test_table}')
      ->fetchField();
    $this->assertEquals(2, $count, 'There were two rows.');
    // Test adding a serial field to an existing table.
    $this->schema
      ->dropTable('test_table');
    $this->schema
      ->createTable('test_table', $table_specification);
    $this->schema
      ->changeField('test_table', 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
      'default' => 0,
    ]);
    $this->schema
      ->addField('test_table', 'test_serial', [
      'type' => 'serial',
      'not null' => TRUE,
    ], [
      'primary key' => [
        'test_serial',
      ],
    ]);
    // Test the primary key columns.
    $method = new \ReflectionMethod(get_class($this->schema), 'findPrimaryKeyColumns');
    $this->assertSame([
      'test_serial',
    ], $method->invoke($this->schema, 'test_table'));
    $this->assertTrue($this->tryInsert(), 'Insert with a serial succeeded.');
    $max1 = $this->connection
      ->query('SELECT MAX([test_serial]) FROM {test_table}')
      ->fetchField();
    $this->assertTrue($this->tryInsert(), 'Insert with a serial succeeded.');
    $max2 = $this->connection
      ->query('SELECT MAX([test_serial]) FROM {test_table}')
      ->fetchField();
    $this->assertTrue($max2 > $max1, 'The serial is monotone.');
    $count = $this->connection
      ->query('SELECT COUNT(*) FROM {test_table}')
      ->fetchField();
    $this->assertEquals(2, $count, 'There were two rows.');
    // Test adding a new column and form a composite primary key with it.
    $this->schema
      ->addField('test_table', 'test_composite_primary_key', [
      'type' => 'int',
      'not null' => TRUE,
      'default' => 0,
    ], [
      'primary key' => [
        'test_serial',
        'test_composite_primary_key',
      ],
    ]);
    // Test the primary key columns.
    $this->assertSame([
      'test_serial',
      'test_composite_primary_key',
    ], $method->invoke($this->schema, 'test_table'));
    // Test adding and removing JSON column.
    $this->schema
      ->addField('test_table', 'test_json', [
      'description' => 'I heard you liked JSON.',
      'type' => 'json',
      'pgsql_type' => 'jsonb',
      'mysql_type' => 'json',
      'sqlite_type' => 'json',
    ]);
    $this->schema
      ->dropField('test_table', 'test_json');
    // Test renaming of keys and constraints.
    $this->schema
      ->dropTable('test_table');
    $table_specification = [
      'fields' => [
        'id' => [
          'type' => 'serial',
          'not null' => TRUE,
        ],
        'test_field' => [
          'type' => 'int',
          'default' => 0,
        ],
      ],
      'primary key' => [
        'id',
      ],
      'unique keys' => [
        'test_field' => [
          'test_field',
        ],
      ],
    ];
    // PostgreSQL has a max identifier length of 63 characters, MySQL has 64 and
    // SQLite does not have any limit. Use the lowest common value and create a
    // table name as long as possible in order to cover edge cases around
    // identifier names for the table's primary or unique key constraints.
    $table_name = strtolower($this->getRandomGenerator()
      ->name(63 - strlen($this->getDatabasePrefix())));
    $this->schema
      ->createTable($table_name, $table_specification);
    $this->assertIndexOnColumns($table_name, [
      'id',
    ], 'primary');
    $this->assertIndexOnColumns($table_name, [
      'test_field',
    ], 'unique');
    $new_table_name = strtolower($this->getRandomGenerator()
      ->name(63 - strlen($this->getDatabasePrefix())));
    $this->assertNull($this->schema
      ->renameTable($table_name, $new_table_name));
    // Test for renamed primary and unique keys.
    $this->assertIndexOnColumns($new_table_name, [
      'id',
    ], 'primary');
    $this->assertIndexOnColumns($new_table_name, [
      'test_field',
    ], 'unique');
    // Check that the ID sequence gets renamed when the table is renamed.
    $this->checkSequenceRenaming($new_table_name);
  }
  
  /**
   * Tests creating a table with database specific data type.
   */
  abstract public function testTableWithSpecificDataType() : void;
  
  /**
   * Tests creating unsigned columns and data integrity thereof.
   */
  public function testUnsignedColumns() : void {
    // First create the table with just a serial column.
    $table_name = 'unsigned_table';
    $table_spec = [
      'fields' => [
        'serial_column' => [
          'type' => 'serial',
          'unsigned' => TRUE,
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'serial_column',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    // Now set up columns for the other types.
    $types = [
      'int',
      'float',
      'numeric',
    ];
    foreach ($types as $type) {
      $column_spec = [
        'type' => $type,
        'unsigned' => TRUE,
      ];
      if ($type == 'numeric') {
        $column_spec += [
          'precision' => 10,
          'scale' => 0,
        ];
      }
      $column_name = $type . '_column';
      $table_spec['fields'][$column_name] = $column_spec;
      $this->schema
        ->addField($table_name, $column_name, $column_spec);
    }
    // Finally, check each column and try to insert invalid values into them.
    foreach ($table_spec['fields'] as $column_name => $column_spec) {
      $this->assertTrue($this->schema
        ->fieldExists($table_name, $column_name), "Unsigned {$column_spec['type']} column was created.");
      $this->assertFalse($this->tryUnsignedInsert($table_name, $column_name), "Unsigned {$column_spec['type']} column rejected a negative value.");
    }
  }
  
  /**
   * Tests adding columns to an existing table with default and initial value.
   */
  public function testSchemaAddFieldDefaultInitial() : void {
    // Test varchar types.
    foreach ([
      1,
      32,
      128,
      256,
      512,
    ] as $length) {
      $base_field_spec = [
        'type' => 'varchar',
        'length' => $length,
      ];
      $variations = [
        [
          'not null' => FALSE,
        ],
        [
          'not null' => FALSE,
          'default' => '7',
        ],
        [
          'not null' => FALSE,
          'default' => substr('"thing"', 0, $length),
        ],
        [
          'not null' => FALSE,
          'default' => substr("\"'hing", 0, $length),
        ],
        [
          'not null' => TRUE,
          'initial' => 'd',
        ],
        [
          'not null' => FALSE,
          'default' => NULL,
        ],
        [
          'not null' => TRUE,
          'initial' => 'd',
          'default' => '7',
        ],
      ];
      foreach ($variations as $variation) {
        $field_spec = $variation + $base_field_spec;
        $this->assertFieldAdditionRemoval($field_spec);
      }
    }
    // Test int and float types.
    foreach ([
      'int',
      'float',
    ] as $type) {
      foreach ([
        'tiny',
        'small',
        'medium',
        'normal',
        'big',
      ] as $size) {
        $base_field_spec = [
          'type' => $type,
          'size' => $size,
        ];
        $variations = [
          [
            'not null' => FALSE,
          ],
          [
            'not null' => FALSE,
            'default' => 7,
          ],
          [
            'not null' => TRUE,
            'initial' => 1,
          ],
          [
            'not null' => TRUE,
            'initial' => 1,
            'default' => 7,
          ],
          [
            'not null' => TRUE,
            'initial_from_field' => 'serial_column',
          ],
          [
            'not null' => TRUE,
            'initial_from_field' => 'test_nullable_field',
            'initial' => 100,
          ],
        ];
        foreach ($variations as $variation) {
          $field_spec = $variation + $base_field_spec;
          $this->assertFieldAdditionRemoval($field_spec);
        }
      }
    }
    // Test numeric types.
    foreach ([
      1,
      5,
      10,
      40,
      65,
    ] as $precision) {
      foreach ([
        0,
        2,
        10,
        30,
      ] as $scale) {
        // Skip combinations where precision is smaller than scale.
        if ($precision <= $scale) {
          continue;
        }
        $base_field_spec = [
          'type' => 'numeric',
          'scale' => $scale,
          'precision' => $precision,
        ];
        $variations = [
          [
            'not null' => FALSE,
          ],
          [
            'not null' => FALSE,
            'default' => 7,
          ],
          [
            'not null' => TRUE,
            'initial' => 1,
          ],
          [
            'not null' => TRUE,
            'initial' => 1,
            'default' => 7,
          ],
          [
            'not null' => TRUE,
            'initial_from_field' => 'serial_column',
          ],
        ];
        foreach ($variations as $variation) {
          $field_spec = $variation + $base_field_spec;
          $this->assertFieldAdditionRemoval($field_spec);
        }
      }
    }
  }
  
  /**
   * Asserts that a given field can be added and removed from a table.
   *
   * The addition test covers both defining a field of a given specification
   * when initially creating at table and extending an existing table.
   *
   * @param array $field_spec
   *   The schema specification of the field.
   *
   * @internal
   */
  protected function assertFieldAdditionRemoval(array $field_spec) : void {
    // Try creating the field on a new table.
    $table_name = 'test_table_' . $this->counter++;
    $table_spec = [
      'fields' => [
        'serial_column' => [
          'type' => 'serial',
          'unsigned' => TRUE,
          'not null' => TRUE,
        ],
        'test_nullable_field' => [
          'type' => 'int',
          'not null' => FALSE,
        ],
        'test_field' => $field_spec,
      ],
      'primary key' => [
        'serial_column',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    // Check the characteristics of the field.
    $this->assertFieldCharacteristics($table_name, 'test_field', $field_spec);
    // Clean-up.
    $this->schema
      ->dropTable($table_name);
    // Try adding a field to an existing table.
    $table_name = 'test_table_' . $this->counter++;
    $table_spec = [
      'fields' => [
        'serial_column' => [
          'type' => 'serial',
          'unsigned' => TRUE,
          'not null' => TRUE,
        ],
        'test_nullable_field' => [
          'type' => 'int',
          'not null' => FALSE,
        ],
      ],
      'primary key' => [
        'serial_column',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    // Insert some rows to the table to test the handling of initial values.
    for ($i = 0; $i < 3; $i++) {
      $this->connection
        ->insert($table_name)
        ->useDefaults([
        'serial_column',
      ])
        ->fields([
        'test_nullable_field' => 100,
      ])
        ->execute();
    }
    // Add another row with no value for the 'test_nullable_field' column.
    $this->connection
      ->insert($table_name)
      ->useDefaults([
      'serial_column',
    ])
      ->execute();
    $this->schema
      ->addField($table_name, 'test_field', $field_spec);
    // Check the characteristics of the field.
    $this->assertFieldCharacteristics($table_name, 'test_field', $field_spec);
    // Clean-up.
    $this->schema
      ->dropField($table_name, 'test_field');
    // Add back the field and then try to delete a field which is also a primary
    // key.
    $this->schema
      ->addField($table_name, 'test_field', $field_spec);
    $this->schema
      ->dropField($table_name, 'serial_column');
    $this->schema
      ->dropTable($table_name);
  }
  
  /**
   * Asserts that a newly added field has the correct characteristics.
   *
   * @internal
   */
  protected function assertFieldCharacteristics(string $table_name, string $field_name, array $field_spec) : void {
    // Check that the initial value has been registered.
    if (isset($field_spec['initial'])) {
      // There should be no row with a value different then
      // $field_spec['initial'].
      $count = $this->connection
        ->select($table_name)
        ->fields($table_name, [
        'serial_column',
      ])
        ->condition($field_name, $field_spec['initial'], '<>')
        ->countQuery()
        ->execute()
        ->fetchField();
      $this->assertEquals(0, $count, 'Initial values filled out.');
    }
    // Check that the initial value from another field has been registered.
    if (isset($field_spec['initial_from_field']) && !isset($field_spec['initial'])) {
      // There should be no row with a value different than
      // $field_spec['initial_from_field'].
      $count = $this->connection
        ->select($table_name)
        ->fields($table_name, [
        'serial_column',
      ])
        ->where("[{$table_name}].[{$field_spec['initial_from_field']}] <> [{$table_name}].[{$field_name}]")
        ->countQuery()
        ->execute()
        ->fetchField();
      $this->assertEquals(0, $count, 'Initial values from another field filled out.');
    }
    elseif (isset($field_spec['initial_from_field']) && isset($field_spec['initial'])) {
      // There should be no row with a value different than '100'.
      $count = $this->connection
        ->select($table_name)
        ->fields($table_name, [
        'serial_column',
      ])
        ->condition($field_name, 100, '<>')
        ->countQuery()
        ->execute()
        ->fetchField();
      $this->assertEquals(0, $count, 'Initial values from another field or a default value filled out.');
    }
    // Check that the default value has been registered.
    if (isset($field_spec['default'])) {
      // Try inserting a row, and check the resulting value of the new column.
      $id = $this->connection
        ->insert($table_name)
        ->useDefaults([
        'serial_column',
      ])
        ->execute();
      $field_value = $this->connection
        ->select($table_name)
        ->fields($table_name, [
        $field_name,
      ])
        ->condition('serial_column', $id)
        ->execute()
        ->fetchField();
      $this->assertEquals($field_spec['default'], $field_value, 'Default value registered.');
    }
  }
  
  /**
   * Tests various schema changes' effect on the table's primary key.
   *
   * @param array $initial_primary_key
   *   The initial primary key of the test table.
   * @param array $renamed_primary_key
   *   The primary key of the test table after renaming the test field.
   *
   * @legacy-covers ::addField
   * @legacy-covers ::changeField
   * @legacy-covers ::dropField
   * @legacy-covers ::findPrimaryKeyColumns
   */
  public function testSchemaChangePrimaryKey(array $initial_primary_key, array $renamed_primary_key) : void {
    $find_primary_key_columns = new \ReflectionMethod(get_class($this->schema), 'findPrimaryKeyColumns');
    // Test making the field the primary key of the table upon creation.
    $table_name = 'test_table';
    $table_spec = [
      'fields' => [
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'other_test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => $initial_primary_key,
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals($initial_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
    // Change the field type and make sure the primary key stays in place.
    $this->schema
      ->changeField($table_name, 'test_field', 'test_field', [
      'type' => 'varchar',
      'length' => 32,
      'not null' => TRUE,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals($initial_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
    // Add some data and change the field type back, to make sure that changing
    // the type leaves the primary key in place even with existing data.
    $this->connection
      ->insert($table_name)
      ->fields([
      'test_field' => 1,
      'other_test_field' => 2,
    ])
      ->execute();
    $this->schema
      ->changeField($table_name, 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals($initial_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
    // Make sure that adding the primary key can be done as part of changing
    // a field, as well.
    $this->schema
      ->dropPrimaryKey($table_name);
    $this->assertEquals([], $find_primary_key_columns->invoke($this->schema, $table_name));
    $this->schema
      ->changeField($table_name, 'test_field', 'test_field', [
      'type' => 'int',
      'not null' => TRUE,
    ], [
      'primary key' => $initial_primary_key,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals($initial_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
    // Rename the field and make sure the primary key was updated.
    $this->schema
      ->changeField($table_name, 'test_field', 'test_field_renamed', [
      'type' => 'int',
      'not null' => TRUE,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field_renamed'));
    $this->assertEquals($renamed_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
    // Drop the field and make sure the primary key was dropped, as well.
    $this->schema
      ->dropField($table_name, 'test_field_renamed');
    $this->assertFalse($this->schema
      ->fieldExists($table_name, 'test_field_renamed'));
    $this->assertEquals([], $find_primary_key_columns->invoke($this->schema, $table_name));
    // Add the field again and make sure adding the primary key can be done at
    // the same time.
    $this->schema
      ->addField($table_name, 'test_field', [
      'type' => 'int',
      'default' => 0,
      'not null' => TRUE,
    ], [
      'primary key' => $initial_primary_key,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals($initial_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
    // Drop the field again and explicitly add a primary key.
    $this->schema
      ->dropField($table_name, 'test_field');
    $this->schema
      ->addPrimaryKey($table_name, [
      'other_test_field',
    ]);
    $this->assertFalse($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals([
      'other_test_field',
    ], $find_primary_key_columns->invoke($this->schema, $table_name));
    // Test that adding a field with a primary key will work even with a
    // pre-existing primary key.
    $this->schema
      ->addField($table_name, 'test_field', [
      'type' => 'int',
      'default' => 0,
      'not null' => TRUE,
    ], [
      'primary key' => $initial_primary_key,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name, 'test_field'));
    $this->assertEquals($initial_primary_key, $find_primary_key_columns->invoke($this->schema, $table_name));
  }
  
  /**
   * Provides test cases for SchemaTest::testSchemaCreateTablePrimaryKey().
   *
   * @return array
   *   An array of test cases for SchemaTest::testSchemaCreateTablePrimaryKey().
   */
  public static function providerTestSchemaCreateTablePrimaryKey() {
    $tests = [];
    $tests['simple_primary_key'] = [
      'initial_primary_key' => [
        'test_field',
      ],
      'renamed_primary_key' => [
        'test_field_renamed',
      ],
    ];
    $tests['composite_primary_key'] = [
      'initial_primary_key' => [
        'test_field',
        'other_test_field',
      ],
      'renamed_primary_key' => [
        'test_field_renamed',
        'other_test_field',
      ],
    ];
    $tests['composite_primary_key_different_order'] = [
      'initial_primary_key' => [
        'other_test_field',
        'test_field',
      ],
      'renamed_primary_key' => [
        'other_test_field',
        'test_field_renamed',
      ],
    ];
    return $tests;
  }
  
  /**
   * Tests an invalid field specification as a primary key on table creation.
   */
  public function testInvalidPrimaryKeyOnTableCreation() : void {
    // Test making an invalid field the primary key of the table upon creation.
    $table_name = 'test_table';
    $table_spec = [
      'fields' => [
        'test_field' => [
          'type' => 'int',
        ],
      ],
      'primary key' => [
        'test_field',
      ],
    ];
    $this->expectException(SchemaException::class);
    $this->expectExceptionMessage("The 'test_field' field specification does not define 'not null' as TRUE.");
    $this->schema
      ->createTable($table_name, $table_spec);
  }
  
  /**
   * Tests converting an int to a serial when the int column has data.
   */
  public function testChangePrimaryKeyToSerial() : void {
    // Test making an invalid field the primary key of the table upon creation.
    $table_name = 'test_table';
    $table_spec = [
      'fields' => [
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field_string' => [
          'type' => 'varchar',
          'length' => 20,
        ],
      ],
      'primary key' => [
        'test_field',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    $this->tryInsertExpectsIntegrityConstraintViolationException($table_name);
    // @todo https://www.drupal.org/project/drupal/issues/3222127 Change the
    //   first item to 0 to test changing a field with 0 to a serial.
    // Create 8 rows in the table. Note that the 5 value is deliberately
    // omitted.
    foreach ([
      1,
      2,
      3,
      4,
      6,
      7,
      8,
      9,
    ] as $value) {
      $this->connection
        ->insert($table_name)
        ->fields([
        'test_field' => $value,
      ])
        ->execute();
    }
    $this->schema
      ->changeField($table_name, 'test_field', 'test_field', [
      'type' => 'serial',
      'not null' => TRUE,
    ]);
    $data = $this->connection
      ->select($table_name)
      ->fields($table_name, [
      'test_field',
    ])
      ->execute()
      ->fetchCol();
    $this->assertEquals([
      1,
      2,
      3,
      4,
      6,
      7,
      8,
      9,
    ], array_values($data));
    try {
      $this->connection
        ->insert($table_name)
        ->fields([
        'test_field' => 1,
      ])
        ->execute();
      $this->fail('Expected IntegrityConstraintViolationException not thrown');
    } catch (IntegrityConstraintViolationException) {
    }
    // Ensure auto numbering now works.
    // We use a >= assertion to allow non-core drivers, that may have specific
    // strategies on automatic incrementing, to run core tests. For example,
    // Oracle will allocate a 10 id with the previous insert that was meant to
    // fail; that id will be discarded, and the insert here will get a new 11
    // id instead.
    $id = $this->connection
      ->insert($table_name)
      ->fields([
      'test_field_string' => 'test',
    ])
      ->execute();
    $this->assertGreaterThanOrEqual(10, $id);
  }
  
  /**
   * Tests adding an invalid field specification as a primary key.
   */
  public function testInvalidPrimaryKeyAddition() : void {
    // Test adding a new invalid field to the primary key.
    $table_name = 'test_table';
    $table_spec = [
      'fields' => [
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'test_field',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    $this->expectException(SchemaException::class);
    $this->expectExceptionMessage("The 'new_test_field' field specification does not define 'not null' as TRUE.");
    $this->schema
      ->addField($table_name, 'new_test_field', [
      'type' => 'int',
    ], [
      'primary key' => [
        'test_field',
        'new_test_field',
      ],
    ]);
  }
  
  /**
   * Tests changing the primary key with an invalid field specification.
   */
  public function testInvalidPrimaryKeyChange() : void {
    // Test adding a new invalid field to the primary key.
    $table_name = 'test_table';
    $table_spec = [
      'fields' => [
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'test_field',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    $this->expectException(SchemaException::class);
    $this->expectExceptionMessage("The 'changed_test_field' field specification does not define 'not null' as TRUE.");
    $this->schema
      ->dropPrimaryKey($table_name);
    $this->schema
      ->changeField($table_name, 'test_field', 'changed_test_field', [
      'type' => 'int',
    ], [
      'primary key' => [
        'changed_test_field',
      ],
    ]);
  }
  
  /**
   * Tests changing columns between types with default and initial values.
   */
  public function testSchemaChangeFieldDefaultInitial() : void {
    $field_specs = [
      [
        'type' => 'int',
        'size' => 'normal',
        'not null' => FALSE,
      ],
      [
        'type' => 'int',
        'size' => 'normal',
        'not null' => TRUE,
        'initial' => 1,
        'default' => 17,
      ],
      [
        'type' => 'float',
        'size' => 'normal',
        'not null' => FALSE,
      ],
      [
        'type' => 'float',
        'size' => 'normal',
        'not null' => TRUE,
        'initial' => 1,
        'default' => 7.3,
      ],
      [
        'type' => 'numeric',
        'scale' => 2,
        'precision' => 10,
        'not null' => FALSE,
      ],
      [
        'type' => 'numeric',
        'scale' => 2,
        'precision' => 10,
        'not null' => TRUE,
        'initial' => 1,
        'default' => 7,
      ],
    ];
    foreach ($field_specs as $i => $old_spec) {
      foreach ($field_specs as $j => $new_spec) {
        if ($i === $j) {
          // Do not change a field into itself.
          continue;
        }
        $this->assertFieldChange($old_spec, $new_spec);
      }
    }
    $field_specs = [
      [
        'type' => 'varchar_ascii',
        'length' => '255',
      ],
      [
        'type' => 'varchar',
        'length' => '255',
      ],
      [
        'type' => 'text',
      ],
      [
        'type' => 'blob',
        'size' => 'big',
      ],
    ];
    foreach ($field_specs as $i => $old_spec) {
      foreach ($field_specs as $j => $new_spec) {
        if ($i === $j) {
          // Do not change a field into itself.
          continue;
        }
        // Note if the serialized data contained an object this would fail on
        // Postgres.
        // @see https://www.drupal.org/node/1031122
        $this->assertFieldChange($old_spec, $new_spec, serialize([
          'string' => "This \n has \\\\ some backslash \"*string action.\\n",
        ]));
      }
    }
  }
  
  /**
   * Asserts that a field can be changed from one spec to another.
   *
   * @param array $old_spec
   *   The beginning field specification.
   * @param array $new_spec
   *   The ending field specification.
   * @param mixed $test_data
   *   (optional) A test value to insert and test, if specified.
   *
   * @internal
   */
  protected function assertFieldChange(array $old_spec, array $new_spec, $test_data = NULL) : void {
    $table_name = 'test_table_' . $this->counter++;
    $table_spec = [
      'fields' => [
        'serial_column' => [
          'type' => 'serial',
          'unsigned' => TRUE,
          'not null' => TRUE,
        ],
        'test_field' => $old_spec,
      ],
      'primary key' => [
        'serial_column',
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_spec);
    // Check the characteristics of the field.
    $this->assertFieldCharacteristics($table_name, 'test_field', $old_spec);
    // Remove inserted rows.
    $this->connection
      ->truncate($table_name)
      ->execute();
    if ($test_data) {
      $id = $this->connection
        ->insert($table_name)
        ->fields([
        'test_field',
      ], [
        $test_data,
      ])
        ->execute();
    }
    // Change the field.
    $this->schema
      ->changeField($table_name, 'test_field', 'test_field', $new_spec);
    if ($test_data) {
      $field_value = $this->connection
        ->select($table_name)
        ->fields($table_name, [
        'test_field',
      ])
        ->condition('serial_column', $id)
        ->execute()
        ->fetchField();
      $this->assertSame($test_data, $field_value);
    }
    // Check the field was changed.
    $this->assertFieldCharacteristics($table_name, 'test_field', $new_spec);
    // Clean-up.
    $this->schema
      ->dropTable($table_name);
  }
  
  /**
   * Tests find primary key columns.
   */
  public function testFindPrimaryKeyColumns() : void {
    $method = new \ReflectionMethod(get_class($this->schema), 'findPrimaryKeyColumns');
    // Test with single column primary key.
    $this->schema
      ->createTable('table_with_pk_0', [
      'description' => 'Table with primary key.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'id',
      ],
    ]);
    $this->assertSame([
      'id',
    ], $method->invoke($this->schema, 'table_with_pk_0'));
    // Test with multiple column primary key.
    $this->schema
      ->createTable('table_with_pk_1', [
      'description' => 'Table with primary key with multiple columns.',
      'fields' => [
        'id0' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'id1' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'id0',
        'id1',
      ],
    ]);
    $this->assertSame([
      'id0',
      'id1',
    ], $method->invoke($this->schema, 'table_with_pk_1'));
    // Test with multiple column primary key and not being the first column of
    // the table definition.
    $this->schema
      ->createTable('table_with_pk_2', [
      'description' => 'Table with primary key with multiple columns at the end and in reverted sequence.',
      'fields' => [
        'test_field_1' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field_2' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'id3' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'id4' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'id4',
        'id3',
      ],
    ]);
    $this->assertSame([
      'id4',
      'id3',
    ], $method->invoke($this->schema, 'table_with_pk_2'));
    // Test with multiple column primary key in a different order. For the
    // PostgreSQL and the SQLite drivers is sorting used to get the primary key
    // columns in the right order.
    $this->schema
      ->createTable('table_with_pk_3', [
      'description' => 'Table with primary key with multiple columns at the end and in reverted sequence.',
      'fields' => [
        'test_field_1' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field_2' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'id3' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'id4' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [
        'id3',
        'test_field_2',
        'id4',
      ],
    ]);
    $this->assertSame([
      'id3',
      'test_field_2',
      'id4',
    ], $method->invoke($this->schema, 'table_with_pk_3'));
    // Test with table without a primary key.
    $this->schema
      ->createTable('table_without_pk_1', [
      'description' => 'Table without primary key.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
    ]);
    $this->assertSame([], $method->invoke($this->schema, 'table_without_pk_1'));
    // Test with table with an empty primary key.
    $this->schema
      ->createTable('table_without_pk_2', [
      'description' => 'Table without primary key.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
        'test_field' => [
          'type' => 'int',
          'not null' => TRUE,
        ],
      ],
      'primary key' => [],
    ]);
    $this->assertSame([], $method->invoke($this->schema, 'table_without_pk_2'));
    // Test with non existing table.
    $this->assertFalse($method->invoke($this->schema, 'non_existing_table'));
  }
  
  /**
   * Tests the findTables() method.
   */
  public function testFindTables() : void {
    // We will be testing with three tables.
    $test_schema = Database::getConnection()->schema();
    // Create the tables.
    $table_specification = [
      'description' => 'Test table.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'default' => NULL,
        ],
      ],
    ];
    $test_schema->createTable('test_1_table', $table_specification);
    $test_schema->createTable('test_2_table', $table_specification);
    $test_schema->createTable('the_third_table', $table_specification);
    // Check the "all tables" syntax.
    $tables = $test_schema->findTables('%');
    sort($tables);
    $expected = [
      // The 'config' table is added by
      // \Drupal\KernelTests\KernelTestBase::containerBuild().
'config',
      'test_1_table',
      // This table uses a per-table prefix, yet it is returned as un-prefixed.
'test_2_table',
      'the_third_table',
    ];
    $this->assertEquals($expected, $tables, 'All tables were found.');
    // Check the restrictive syntax.
    $tables = $test_schema->findTables('test_%');
    sort($tables);
    $expected = [
      'test_1_table',
      'test_2_table',
    ];
    $this->assertEquals($expected, $tables, 'Two tables were found.');
    // Check '_' and '%' wildcards.
    $test_schema->createTable('test3table', $table_specification);
    $test_schema->createTable('test4', $table_specification);
    $test_schema->createTable('testTable', $table_specification);
    $test_schema->createTable('test', $table_specification);
    $tables = $test_schema->findTables('test%');
    sort($tables);
    $expected = [
      'test',
      'test3table',
      'test4',
      'testTable',
      'test_1_table',
      'test_2_table',
    ];
    $this->assertEquals($expected, $tables, 'All "test" prefixed tables were found.');
    $tables = $test_schema->findTables('test_%');
    sort($tables);
    $expected = [
      'test3table',
      'test4',
      'testTable',
      'test_1_table',
      'test_2_table',
    ];
    $this->assertEquals($expected, $tables, 'All "/^test..*?/" tables were found.');
    $tables = $test_schema->findTables('test%table');
    sort($tables);
    $expected = [
      'test3table',
      'testTable',
      'test_1_table',
      'test_2_table',
    ];
    $this->assertEquals($expected, $tables, 'All "/^test.*?table/" tables were found.');
    $tables = $test_schema->findTables('test_%table');
    sort($tables);
    $expected = [
      'test3table',
      'test_1_table',
      'test_2_table',
    ];
    $this->assertEquals($expected, $tables, 'All "/^test..*?table/" tables were found.');
    $tables = $test_schema->findTables('test_');
    sort($tables);
    $expected = [
      'test4',
    ];
    $this->assertEquals($expected, $tables, 'All "/^test./" tables were found.');
  }
  
  /**
   * Tests handling of uppercase table names.
   */
  public function testUpperCaseTableName() : void {
    $table_name = 'A_UPPER_CASE_TABLE_NAME';
    // Create the tables.
    $table_specification = [
      'description' => 'Test table.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'default' => NULL,
        ],
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_specification);
    $this->assertTrue($this->schema
      ->tableExists($table_name), 'Table with uppercase table name exists');
    $this->assertContains($table_name, $this->schema
      ->findTables('%'));
    $this->assertTrue($this->schema
      ->dropTable($table_name), 'Table with uppercase table name dropped');
  }
  
  /**
   * Tests table schema methods when a view exists.
   */
  public function testSchemaMethodsWithView() : void {
    // We will be testing with three tables.
    $test_schema = Database::getConnection()->schema();
    // Create the tables.
    $table_specification = [
      'description' => 'Test table.',
      'fields' => [
        'id' => [
          'type' => 'int',
          'default' => NULL,
          'description' => 'Test field.',
        ],
      ],
    ];
    $test_schema->createTable('test_table', $table_specification);
    // Create a view to ensure it is not found.
    Database::getConnection()->query('create view {test_view} as select * from {test_table}');
    // Test \Drupal\Core\Database\Schema::tableExists().
    $this->assertTrue($this->schema
      ->tableExists('test_table'), 'Table exists');
    $this->assertFalse($this->schema
      ->tableExists('test_view'), 'View is not checked by tableExists() method');
    // Test \Drupal\Core\Database\Schema::findTables().
    $tables = array_values($test_schema->findTables('t%'));
    $this->assertEquals([
      'test_table',
    ], $tables, 'All tables were found.');
    // Test \Drupal\Core\Database\Schema::getComment().
    $this->checkSchemaComment('Test table.', 'test_table');
    $this->checkSchemaComment('Test field.', 'test_table', 'id');
    $this->checkSchemaComment(FALSE, 'test_view');
    $this->checkSchemaComment(FALSE, 'test_view', 'id');
    $this->checkSchemaComment(FALSE, 'does_not_exist');
    $this->checkSchemaComment(FALSE, 'does_not_exist', 'id');
    // Clean up the view.
    Database::getConnection()->query('drop view {test_view}');
  }
  
  /**
   * Tests default values after altering table.
   */
  public function testDefaultAfterAlter() : void {
    $table_name = 'test_table';
    // Create the table.
    $table_specification = [
      'description' => 'Test table.',
      'fields' => [
        'column1' => [
          'type' => 'int',
          'default' => NULL,
        ],
        'column2' => [
          'type' => 'varchar',
          'length' => 20,
          'default' => NULL,
        ],
        'column3' => [
          'type' => 'int',
          'default' => 200,
        ],
        'column4' => [
          'type' => 'float',
          'default' => 1.23,
        ],
        'column5' => [
          'type' => 'varchar',
          'length' => 20,
          'default' => "'s o'clock'",
        ],
        'column6' => [
          'type' => 'varchar',
          'length' => 20,
          'default' => "o'clock",
        ],
        'column7' => [
          'type' => 'varchar',
          'length' => 20,
          'default' => 'default value',
        ],
      ],
    ];
    $this->schema
      ->createTable($table_name, $table_specification);
    // Insert a row and check that columns have the expected default values.
    $this->connection
      ->insert($table_name)
      ->fields([
      'column1' => 1,
    ])
      ->execute();
    $result = $this->connection
      ->select($table_name, 't')
      ->fields('t', [
      'column2',
      'column3',
      'column4',
      'column5',
      'column6',
      'column7',
    ])
      ->condition('column1', 1)
      ->execute()
      ->fetchObject();
    $this->assertNull($result->column2);
    $this->assertSame('200', $result->column3);
    $this->assertSame('1.23', $result->column4);
    $this->assertSame("'s o'clock'", $result->column5);
    $this->assertSame("o'clock", $result->column6);
    $this->assertSame('default value', $result->column7);
    // Force SQLite schema to create a new table and copy data by adding a not
    // field with an initial value.
    $this->schema
      ->addField('test_table', 'new_column', [
      'type' => 'varchar',
      'length' => 20,
      'not null' => TRUE,
      'description' => 'Added new column',
      'initial' => 'test',
    ]);
    // Test that the columns default values are still correct.
    $this->connection
      ->insert($table_name)
      ->fields([
      'column1' => 2,
      'new_column' => 'value',
    ])
      ->execute();
    $result = $this->connection
      ->select($table_name, 't')
      ->fields('t', [
      'column2',
      'column3',
      'column4',
      'column5',
      'column6',
      'column7',
    ])
      ->condition('column1', 2)
      ->execute()
      ->fetchObject();
    $this->assertNull($result->column2);
    $this->assertSame('200', $result->column3);
    $this->assertSame('1.23', $result->column4);
    $this->assertSame("'s o'clock'", $result->column5);
    $this->assertSame("o'clock", $result->column6);
    $this->assertSame('default value', $result->column7);
  }
  
  /**
   * Tests handling with reserved keywords for naming tables, fields and more.
   */
  public function testReservedKeywordsForNaming() : void {
    $table_specification = [
      'description' => 'A test table with an ANSI reserved keywords for naming.',
      'fields' => [
        'primary' => [
          'description' => 'Simple unique ID.',
          'type' => 'int',
          'not null' => TRUE,
        ],
        'update' => [
          'description' => 'A column with reserved name.',
          'type' => 'varchar',
          'length' => 255,
        ],
      ],
      'primary key' => [
        'primary',
      ],
      'unique keys' => [
        'having' => [
          'update',
        ],
      ],
      'indexes' => [
        'in' => [
          'primary',
          'update',
        ],
      ],
    ];
    // Creating a table.
    $table_name = 'select';
    $this->schema
      ->createTable($table_name, $table_specification);
    $this->assertTrue($this->schema
      ->tableExists($table_name));
    // Finding all tables.
    $tables = $this->schema
      ->findTables('%');
    sort($tables);
    $this->assertEquals([
      'config',
      'select',
    ], $tables);
    // Renaming a table.
    $table_name_new = 'from';
    $this->schema
      ->renameTable($table_name, $table_name_new);
    $this->assertFalse($this->schema
      ->tableExists($table_name));
    $this->assertTrue($this->schema
      ->tableExists($table_name_new));
    // Adding a field.
    $field_name = 'delete';
    $this->schema
      ->addField($table_name_new, $field_name, [
      'type' => 'int',
      'not null' => TRUE,
    ]);
    $this->assertTrue($this->schema
      ->fieldExists($table_name_new, $field_name));
    // Dropping a primary key.
    $this->schema
      ->dropPrimaryKey($table_name_new);
    // Adding a primary key.
    $this->schema
      ->addPrimaryKey($table_name_new, [
      $field_name,
    ]);
    // Check the primary key columns.
    $find_primary_key_columns = new \ReflectionMethod(get_class($this->schema), 'findPrimaryKeyColumns');
    $this->assertEquals([
      $field_name,
    ], $find_primary_key_columns->invoke($this->schema, $table_name_new));
    // Dropping a primary key.
    $this->schema
      ->dropPrimaryKey($table_name_new);
    // Changing a field.
    $field_name_new = 'where';
    $this->schema
      ->changeField($table_name_new, $field_name, $field_name_new, [
      'type' => 'int',
      'not null' => FALSE,
    ]);
    $this->assertFalse($this->schema
      ->fieldExists($table_name_new, $field_name));
    $this->assertTrue($this->schema
      ->fieldExists($table_name_new, $field_name_new));
    // Adding an unique key.
    $unique_key_name = $unique_key_introspect_name = 'unique';
    $this->schema
      ->addUniqueKey($table_name_new, $unique_key_name, [
      $field_name_new,
    ]);
    // Check the unique key columns.
    $introspect_index_schema = new \ReflectionMethod(get_class($this->schema), 'introspectIndexSchema');
    $this->assertEquals([
      $field_name_new,
    ], $introspect_index_schema->invoke($this->schema, $table_name_new)['unique keys'][$unique_key_introspect_name]);
    // Dropping an unique key.
    $this->schema
      ->dropUniqueKey($table_name_new, $unique_key_name);
    // Dropping a field.
    $this->schema
      ->dropField($table_name_new, $field_name_new);
    $this->assertFalse($this->schema
      ->fieldExists($table_name_new, $field_name_new));
    // Adding an index.
    $index_name = $index_introspect_name = 'index';
    $this->schema
      ->addIndex($table_name_new, $index_name, [
      'update',
    ], $table_specification);
    $this->assertTrue($this->schema
      ->indexExists($table_name_new, $index_name));
    // Check the index columns.
    $this->assertEquals([
      'update',
    ], $introspect_index_schema->invoke($this->schema, $table_name_new)['indexes'][$index_introspect_name]);
    // Dropping an index.
    $this->schema
      ->dropIndex($table_name_new, $index_name);
    $this->assertFalse($this->schema
      ->indexExists($table_name_new, $index_name));
    // Dropping a table.
    $this->schema
      ->dropTable($table_name_new);
    $this->assertFalse($this->schema
      ->tableExists($table_name_new));
  }
  
  /**
   * Tests changing a field length.
   */
  public function testChangeSerialFieldLength() : void {
    $specification = [
      'fields' => [
        'id' => [
          'type' => 'serial',
          'not null' => TRUE,
          'description' => 'Primary Key: Unique ID.',
        ],
        'text' => [
          'type' => 'text',
          'description' => 'A text field',
        ],
      ],
      'primary key' => [
        'id',
      ],
    ];
    $this->schema
      ->createTable('change_serial_to_big', $specification);
    // Increase the size of the field.
    $new_specification = [
      'size' => 'big',
      'type' => 'serial',
      'not null' => TRUE,
      'description' => 'Primary Key: Unique ID.',
    ];
    $this->schema
      ->changeField('change_serial_to_big', 'id', 'id', $new_specification);
    $this->assertTrue($this->schema
      ->fieldExists('change_serial_to_big', 'id'));
    // Test if we can actually add a big int.
    $id = $this->connection
      ->insert('change_serial_to_big')
      ->fields([
      'id' => 21474836470,
    ])
      ->execute();
    $id_two = $this->connection
      ->insert('change_serial_to_big')
      ->fields([
      'text' => 'Testing for ID generation',
    ])
      ->execute();
    $this->assertEquals($id + 1, $id_two);
  }

}