Several intervals in a test instruction

In this example 12, 24 and 36 are valid test values or valid equivalence classes. For 2-digit entry fields all other values between 0 and 99 are invalid. This can be expressed by several intervals aligned with one another:

In test cases with invalid entries for this condition LF‑ET first selects one of the aligned intervals at random and calculates a specific test value for this entry, as required, as an average value or a random value of this interval:

For an optional boundary value analysis the lower and upper boundary values of all intervals are used then.

All valid and invalid values between 0 and 99 are determined using the above intervals without gaps and overlaps. If the intervals in rows 1 to 3 are replaced with simple numerical values, e.g. [12:12] with 12, auto­matic interval check produces warnings concerning interval gaps that have thus appeared.