I read this in an article online about evolution and intelligent design theory.

'Evolutionary theory - first proposed by Charles Darwin in 1859 - explains the diversity of plants and animals as the result of natural selection. It is based on observations of the natural world and can be tested.'

No. It cant be tested. Natural selection can be observed and tested.
Micro-Evolution (Loss of Genetic code from mutation) causing variation within the same species can be observed.
Macro-Evolution (Addition of Genetic code - change from one species to another) has never been observed, and as such, can never be tested.

The 'Missing Link' is missing for a reason.