Test case design--Boundary value method

Reproduced

Boundary value analysis is also a black box test method, a supplement of the moderately equivalent class analysis method is learned from long-term test work experience that a large number of errors occur on the input or output boundary. Therefore, to design test cases for various boundary conditions, more errors can be detected.
such as: X>8, then the boundary value can be {8,9}, or {7,8,9}
If the program is written in X>=8, 8 can be measured to
If the program is written in X<8, it can be measured by 7,9.
If the program is written in X<>8, it can be measured by 7.

principles for selecting test Cases
First, if the input condition specifies the range of values, then the boundary value that has just reached this range should be taken, and the value just above the bounds of the range as the test input number.
such as: an input file should include 1~255 records, the test case should be 1 and 255, should also take 0, 2 and 254, 256, etc.;
Three, according to the specification of each output condition, the use of rule I.
Four, according to the specification of each output condition, the use of rule two.
If the program specification indicates that the input field or output field is an ordered set (such as ordered table, sequential file, etc.), then the first and last element of the collection should be selected as the test case;
Steps for boundary value analysis
Boundary value analysis uses the same division as the equivalence class partitioning method, except that the boundary value analysis assumes that the error is more on the dividing boundary, so the test case is designed on the boundary of the equivalence class and on both sides of the case;
1. Divide the input or output parameters of the software into equivalent classes;
2. Boundary value analysis is performed on the basis of equivalence class. In general, if the boundary value is already covered by the equivalence class, it can not be considered;
3. Combining the boundary values as input data for the test case;

Integrated practice of equivalence class + boundary value

Test case design--Boundary value method