Two different things sit in this family, and confusing them is the usual mistake.
Language proficiency
Tests in Dutch, English, French, German, Italian, Mandarin, Portuguese and Spanish. Each asks about understanding and use of that language.
Use one when the role genuinely requires working in that language: a support role for a market, a sales role in a territory, a team whose working language is not English.
English grammar and spelling
Different tests, with a different job. These are about written accuracy in English: grammar, and spelling.
Use one when the role produces writing that customers or regulators will read. Do not use one as a general intelligence proxy, which is what they most often get used for.
The care these need
Language tests screen on a characteristic closely tied to nationality and national origin, and in most jurisdictions that makes them higher risk than any other test in the library.
Three rules that keep you on solid ground:
- Only test a language the job actually requires. If the role can be done in English, do not test another language. If the role does not involve writing, do not test spelling.
- Match the level to the job, not to a native speaker. A support role needs to be understood, not to pass an exam. Choose the Foundation level where it exists.
- Write down why before you send it. "This role answers written complaints from customers in German" is a reason. "It is good to have" is not.
This is not legal advice, and if you are unsure about a specific role, take proper advice for your jurisdiction.
Reading a score
A percentage with a test average, the same as the other scored tests. Remember that a test of written English measures written English. It does not measure how well someone will speak to a customer, and it certainly does not measure how clever they are.
A candidate whose written accuracy is imperfect and whose reasoning scores are strong is very often exactly the person you want, working in their second or third language.
Pairing language tests with others
A language test tells you about the language. Pair it with something that tells you about the work, such as a workplace skills test for a customer-facing role.