Due to the coronavirus crisis, there are an indefinite postpone of the start of new term and cancelation of IELTS and TOEFL exams in China, Admission Office of University of Twente confirmed that application deadline is still 1 May for a completed application with all the required documents submitted via Osiris. However, Admission Office understands the current situation; if students don’t have at the moment he/she is uploading their documents (IELTS or TOEFL), then a pdf (word) can be uploaded which explains why they don’t have at the moment such a document, and that they will upload it after.
For example, the student can mention that as prevention and control measure of the coronavirus outbreak, the IELTS, TOEFL or GMAT tests have been canceled during February (some in March too) by China's Ministry of Education - according to the documents they need to upload. And that they are planning on taking them somewhere in April or May, as soon as the test dates get restored.
So the deadline (May 1) is to have completed their application, with the explanation letter as attachment instead of IELTS or TOEFL, at this moment.