CEFR or Common European Framework of Reference for Languages is a standard acknowledged internationally for defining language proficiency. CEFR is widely recognized throughout Europe and is increasingly common worldwide. That is why the UK government also apply one of the CEFR tests, which is the B1 English test to assess those applying for the citizenship of the country. The applier can book the test on two approved institutions through websites such as the one on britishlifeskills.com.
Other standard English tests may assess some level of proficiency, but not the entire CEFR scale. The CEFR was drafted by the Council of Europe in 1990 as part of a broader effort to promote cooperation among language teachers in all countries in Europe. The Council of Europe also wants to increase the clarity for entrepreneurs and educational institutions that need to evaluate the language skills of prospective employees/students. This framework is intended for use in teaching and assessment.