"The test today was easy."
Can you please help me understand when to use YASASHII? And when to use KANTAN in this context?
優しい is actually a homophone of 易しい (which has a similar, but distinct, meaning to 簡単) and is usually used to describe people. From my experience, 簡単 tends to be used more in common speech (possibly due to the confusion that might arise between 優しい and 易しい, though context would usually make the intent clear). However, 易しい seems to carry the meaning of "easy to understand" whereas 簡単 tends to mean "simple", though both do translate to "easy" and can be interchangeable.
Literally it does mean today's test but it can be translated to the test today as well. 今日のテスト is perfectly natural in Japanese. Try not to translate so literally between Japanese and English all the time otherwise you will encounter a lot of problems.
Is the 'no' necessary? Doesn't it change the meaning from 'The test today' to 'today's test'?
The particle の indicates possession. It is necessary in this case; you can't make a compound word out of 今日 and テスト. "the test today" and "today's test" would mean the same thing here.
I understand that is necessary, but they should change in Today's test. It means the same semantically, but gramatically in the first sentence (The test today...) "today" is an adverb, in the second (Today's test) "today" is a name. And an adverb is not able to possess something.
I was about to answer KANTAN DESU. but it's KANTAN DESHITA. can someone explain why DeShiTa and not DeSu?