Give me a hint. What kind of hassle am I facing if doc suspects esophageal stricture? What is required to diagnose?

Endoscopy. To diagnose an esophageal stricture, one would need an esophagram to characterize a potential stricture. Then an endoscopy to look at the esophagus and stomach, and biopsy any identified strictures.
Swallowing problems. Esophageal strictures often cause trouble swallowing. They are usually from long standing reflux or 'eosinophilic esophagits' caused by certain food allergies. If bothersome they might need to be dilated or stretched through and endoscope by a specialist. You need to see a gastroenterologist if you think you have an esophageal stricture. They will guide you.
Depends on cause. The primary symptom associated with esophageal stricture is difficulty swallowing or food getting stuck. Babies can have this an a congenital anomaly, while the most likely non-malignant cause beyond childhood is probably ge reflux. The diagnosis can be made with a barium swallow. Once this is confirmed, esophagoscopy to biopsy & possibly dilate the stricture is appropriate.
See below. This can be found with either a barium swallow (x-ray while swallowing some oral contrast liquid) or a look down the esophagus with a flexible scope while sedated. This is painless and easy to treat. The most common cause is reflux, however, one of the main reasons to look is to ensure there is no cancer in the esophagus causing the narrowing.