This has several practical advantages; the more grades a student gets throughout the term, the more objective the final evaluation is likely to be. Also, if a student does not do very well in one test, she knows she will be given many other chances to improve her overall score. I believe that this type of continuous assessment motivates students to work systematically and incessantly, which is highly beneficial, especially in an L2 classroom, where sporadic bursts of cramming would not suffice.
My philosophy is that the final grade should be as objective as possible. I suppose that this can be easily achieved if it includes evaluation of various language areas, such as vocabulary and grammar, and skills, i.e. listening, speaking, writing and reading. I find it useful if each of these areas and skills is further dissected into sub-areas and sub-skills during the evaluation process. So when I distribute corrected essays, for example, my students know what the final mark consists of; there is a separate score for vocabulary (which includes categories such as spelling, accuracy, relevance and range), a score for grammar (this is comprised of accuracy and range), and separate scores for cohesion, coherence, content etc. That said, when two students get the same mark, it does not mean that their achievement is identical; each of them has different strengths and struggles with specific areas of the target language.
To assess my students, I use short tests as well as progress tests on a regular basis. Once in a while I also use proficiency tests to discover what their current level is as described by the CEFR (The Common European Framework of Reference). I am aware of the fact that this can be somewhat demotivating for weaker students. However, this approach is a must in my teaching context as upon finishing secondary education, all our students will take a B1-B2 English exam. That is why they need to know which areas to work on.
Nevertheless, there are students who do their best to succeed, but in the end they often fail to get a decent grade. On that account, I also consider participation and effort when evaluating my students. For example, with young learners, I regularly do project work. The students are asked to write a coherent piece text on a specific topic (a poster, leaflet, comic), which they illustrate, colour, etc. As long as they manage to get the message across, I never subtract points for incorrect use of grammar or vocabulary. My main criterion is the effort they put into their work. This is highly motivating and enables weaker students to improve their existing score.
To conclude, I believe that assessment should not be used to threaten or discourage students. On the contrary, it should motivate them to improve their language abilities and to make visible progress. Through continuous assessment, the teacher can highlight students' strengths as well as help them work on their current weaknesses and problems.