Is it Important to Test Students?

In my opinion testing is very important, because depending on the type of test the students take you can tell their level of English, ho much have they learned, etc.

Tests are usually made up of two types of questions:
 Discrete questions-Where the test focuses on a specific language point.
Integrative questions-Where different skills are tested at the same time.

There two ways to mark these types of questions:
Objectively-There is only one correct answer.
Subjectively-The answer depends on the person marking the exam.

Also on the other hand there are three criteria to make sure a test is well made:
The test has to be fair and appropriate to the students level.
The test will be easy to mark.
The test will give clear results to serve the purpose for which it was made.

Some students may become stressed if they know a test is coming, so some teacher like to test students without them even realizing they're being tested. For this teachers will run the activities as they usually do but pay special attention to a group of students and do the same thing for the next classes with different group until they have "tested" the whole class.
The teacher can then see if students surpass his expectations, meet his expectations, have problems meeting his expectations, or if students don't meet expectations at all.
Some activities teachers use to test students without them knowing are:
Gap-fills
Sentence Transformations
Sentence Construction and Deconstruction
Two-Option Answers
Matching

Here we have some examples of different types of tests:
Placement:Aims to sort new students into teaching groups of same level
Diagnostic: Aims to tell a student how well he/she has learned a particular course element.
Achievement: Aims to measure what has been learned over a long period of time.
Proficiency: Aims to see the student's ability to apply what they have learned.

In conclusion testing is very important for both students and teachers alike, students will know their mistakes and should focus on improving them and teachers will know where most of his students have problems.