test: add test for Fore::modifyColumn() and null

Author: kenjis

tests/system/Database/Live/ForgeTest.php

@@ -17,6 +17,7 @@
 use CodeIgniter\Test\DatabaseTestTrait;
 use Config\Database;
 use RuntimeException;
+use stdClass;
 use Tests\Support\Database\Seeds\CITestSeeder;
 
 /**
@@ -1281,6 +1282,46 @@ public function testModifyColumnRename()
         $this->forge->dropTable('forge_test_three', true);
     }
 
+    public function testModifyColumnNull()
+    {
+        $this->forge->dropTable('forge_test_modify', true);
+
+        $this->forge->addField([
+            'col1' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => true],
+            'col2' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => true],
+            'col3' => ['type' => 'VARCHAR', 'constraint' => 255, 'null' => true],
+        ]);
+        $this->forge->createTable('forge_test_modify');
+
+        $this->forge->modifyColumn('forge_test_modify', [
+            'col1' => ['type' => 'VARCHAR', 'constraint' => 1],
+            'col2' => ['type' => 'VARCHAR', 'constraint' => 1, 'null' => true],
+            'col3' => ['type' => 'VARCHAR', 'constraint' => 1, 'null' => false],
+        ]);
+
+        $this->db->resetDataCache();
+
+        $col1 = $this->getMetaData('col1');
+        $this->assertTrue($col1->nullable);
+        $col2 = $this->getMetaData('col2');
+        $this->assertTrue($col2->nullable);
+        $col3 = $this->getMetaData('col3');
+        $this->assertFalse($col3->nullable);
+
+        $this->forge->dropTable('forge_test_modify', true);
+    }
+
+    private function getMetaData(string $column): stdClass
+    {
+        $fields = $this->db->getFieldData('forge_test_modify');
+
+        return $fields[array_search(
+            $column,
+            array_column($fields, 'name'),
+            true
+        )];
+    }
+
     public function testConnectWithArrayGroup()
     {
         $group = config('Database');