Testing students' knowledge whether a teacher-made test or a standardized test can cause anxiety for students. This is a difficult question not knowing exactly what your child experiences when he/she knows there is a test. So if you could give us a little more information that would be helpful. Answers to questions like:
How old is your child?
What type of tests does your child have difficulty with (subject area)?
Does your child have trouble learning the information in the first place?
Is the problem not understanding the directions?
Does your child have anxiety before a test?
How does your child feel after the test?
Any information you can give us will allow us to give you better advice.