Not true. Fissile products leave very distinct traces of their origins. All you need are trace samples of the material they are enriching, and a knowledge of the weapons' design, both of which Western intelligence agencies already have.
And, when results are back, from Western labs Tehran will decry as lying, what is anyone going to do about it?
Answer: Nothing
Iran has a Uranium based nuke program, very easy to trace as we constantly sample the byproducts of their refining process.
Iran will not attack Israel with nukes as they would be Iraq’d and they know it.
Iran’s threat is the marketing of nuke technology to the Burma’s and Venezuela’s of this world.
Iran could do a lot of posing and strutting and braying like mules.
We talk one thing and do another. This ineffective embargo and sanctions only affects what they buy. If we want to stomp on Iran we have to embargo what they sell.
These constant media reports of Iran the boogeyman are only distractions that pander to our national lack of understanding of Iran and also pander to the Israeli hype program.