For a single Photon , you really can't perform two tests.
If you perform a test that fixes the position of the photon at a point you cannot also perform a test that finds a diffraction pattern , you may choose either one but never both .
Very simple , the photon is destroyed by the first test so it cannot be tested again.
For slightly larger particles or waves two tests can be performed , but the accuracy of one is affected by the other.
Heisenburg proved that there is a minimum energy required for any test , so there is a directly related limit on precision in very small measurements. at the tinyness of a single photon , the minimum energy is near the size of the photon itself.
I wonder if there might be a dodge for sidestepping the Heisenburg limits on precision? Experiments like this bring us close.