Do I need a corona test to travel to Iran?

If you're over twelve years old, you'll need a test.

But the requirements are much more complicated than that. Look at the IATA Travel Regulations Map, pass the "I Am Not a Robot" challenge, and select Iran on the map. Current entry requirements will appear in a pop up window.

The text can't be copied. In brief:

• Travelers who've been in or transited through specified countries within the last 14 days can't enter Iran unless they are Iranian nationals or residents.
• Arriving passengers need a covid test of specific type with a report that includes specific information (and a QR code if the passenger is traveling to Isfahan) and is in English or is approved by an Iranian consulate. This requirement does not apply to passengers younger than 12 years.
• Travelers (with some exceptions) must have a vaccination certificate in English showing vaccination (types are listed) with an accepted vaccine within the specified time periods. This requirement does not apply to nationals of Iran nor to passengers younger than 12 years.
• Passengers from listed countries could be subject to a covid-19 test on arrival. This requirement does not apply to nationals of Iran nor to passengers younger than 12 years.
• Any passenger could be subject to a Covid-19 test upon arrival, and quarrantine at their own expense.
• Nationals and residents of Iran arriving from or having transited through specified countries in the last 14 days are subject to a Covid-19 test on arrival and quarantine for 14 days at a hotel in the airport.
• Passengers must complete a Self-Declaration form.
• Passengers must obtain an E-Visa and possess an E-visa confirmation.
• Passengers must possess return/onward tickets.

Remember that this is the information I found on 26 February 2022. Requirements change frequently. Pay attention, and check again before you depart.