15. A wine storage system uses a control device that measures the wine cell temperature T (measured in °C, rounded to the nearest degree) and alarms the user if it deviates from the optimal value of 12, according to the following rules:

- if T = 12, the system says, “optimal temperature”
- if T < 12, the system says, “temperature is too low!”
- if T > 12, the system says, “temperature is too high!”

You want to use the 3-point boundary value analysis (BVA) to verify the behavior of the control device. A test input is a temperature in °C provided by the device.

What is the MINIMAL set of test inputs that achieves 100% of the desired coverage?

Explanation / Rationale

There are three equivalence partitions: {..., 10, 11}, {12}, and {13, 14, ...}.

The boundary values are 11, 12 and 13. In the three-point boundary value analysis for each boundary, we need to test the boundary and both its neighbors, so:

- for 11 we test 10, 11, 12
- for 12 we test 11, 12, 13
- for 13 we test 12, 13, 14

Altogether we need to test 10, 11, 12, 13, and 14

Thus:

a) Is not correct

b) Is not correct

c) Is correct

d) Is not correct