Do I have to take English test for Canada immigration

I mailed out my application fo Canadian immigration in Jan. Today I received a letter from the office saying that The material that I provide does not support the level of proficiency indicated on my form. They suggested me to take official test. I got my mastre degree in USA and have been lived in US for 7 years. I wrote a letter indicating my education and experience in US, but it seems it did not help. At the end of the letter, it says that if you do not provide the results of language testing, an assessment of you proficiency will be made based on the information you have provided. This could result in fewer points being awarded for language ability which will influence your overall assessment as a skilled worker.

Please give me some suggestion! Taking those test not only cost 140 bucks, but alos takes a lot of time. Do I have to or I can just ignore it?

Thank you very much!