Should QA test strictly in terms of a black box?

Question

Assuming unit tests are handled by development, is there any reason QA needs to know information about how the product works? By this, I mean, do they need to know what is going on in the background, and should they test product segments without using the normal user interface? For example, it would be advisable for the tester to enter the database and manually change the values ​​to find out what will happen?

EDIT:
Suppose we are working with an application that will not be used by developers, we are not working on something with an attached API.

Answer 1

, . . , QA . , , , QA .

, , , QA . , , , , .

Answer 2

, . , db , . QA , , , .. .

, : , QA ( ), QA, : , . , QA , . , , , , . .

Answer 3

, . .

Black-box test - , , , .

, , , .

Answer 4

, , QA , . . . , - QA . dev.

Answer 5

, , QA . , , , , , , , ( ) .

, QA - . , , , , , QA " ", .

Answer 6

, , QA , . , .

: QA , , , .

QA - , . , , , .

UPDATE
, .

@testerab.

QA , -; 2. . " ". , , , QA, - .

-, , - ( ). QA, . QA, , . , , QA, , .

. , . , , . / , . MS Word CRM .

QA , . . . . , , .

, QA .

. , QA . - EDI, .

API. QA, , API-, , . , QA , .

, , . . , "ABC" , .

---

"" , , , , . , , .. QA , , - .

---

SDET: API , , , , QA. , .

, , API. , , . . , , , . , , , "" .

, , , , . , . QA, , .

---

, QA. , , , , .

: 1. ; 2. ; 3. , . 4. , .

: 1. , ; 2. ; 3. ; 4. ""; 5. , , .

Answer 7

I think the hybrid approach works well. If you use a combination of white box testing (unit tests) and black box testing, you get better coverage. Each has its pros and cons, but they partially cover the shortcomings in the other.

Understanding the inner workings of the code will lead you to test in a certain way, which is not always the best way to identify specific problems.