Really? I would have assumed that resistors are so cheap that testing them is more expensive than designing the process up front around the tolerance.
You'll find that their values are almost exactly: stated_value+/-tolerance rather than a range of values.
i.e a 100k 5% resistor will be almost exactly either 105k or 95k not some number in between.
They're probably batch controlled. There is no way every resistor is being tested for compliance given how cheap SMT resistors are.
Really? I would have assumed that resistors are so cheap that testing them is more expensive than designing the process up front around the tolerance.