## 4 RTC Device Functional Test Determination Method
For each check \(\mathbf{d}_{j}\), there is a set of elementary algorithms \(a_{i}^{K}\). The set of elementary algorithms is the test path \(\mathbf{d}_{j}\);
4. The set of test execution costs \(C=\{c_{j}\}\) is available;
5. A test set \(\mathbf{D}_{\mathbf{opt}}\) that is required and sufficient for the purposes of checking the functional state needs to be determined. This set is optimal for a specified criterion. Determining an optimal check set from the set of all checks is time-consuming and sometimes complicated. This is due to the size of available checks \(\mathbf{D}_{\mathbf{d}}\) and the multitude of target check sets that can be generated. A suboptimal check set can be obtained by determining a subset of target checks \(\mathbf{D}_{\mathbf{c}}\) from a set of available checks \(\mathbf{D}_{\mathbf{d}}\). Hence, tests that do not provide information on the tested configuration elements are eliminated. Next, necessary checks \(\mathbf{D}_{\mathbf{n}}\) should be determined from the set \(\mathbf{D}_{\mathbf{c}}\). The obtained set is checked for being sufficient to inspect the functional state of the devices and whether all tested algorithms are covered by the intended tests. Meeting the condition allows the commencement of test execution. If this set is not a sufficient set, it should be supplemented with additional redundant checks \(\mathbf{D}_{\mathbf{n}\mathbf{d}}\). Simultaneously, a redundant set is optimized in terms of the specific criterion and adopted constraints. According to the assumptions, this criterion is a generalized cost of individual tests, while the constraints are the selection of tests providing the most diagnostic information [49; 50; 51; 52; 53]. The optimization criterion involves selecting checks with the lowest cost. The overall diagram of an algorithm for determining an optimal test set is shown in Figure 1[48]. To sum up, the stages of the method are as follows:  
* Collection of station documentation: schematic diagram, locking sheets, etc. ;
* Development of a modified locking sheet based on the documentation, in the form of control and monitoring algorithms;
* Determination of a set of \(\mathbf{D}_{\mathbf{d}}\) available checks, which is a set of all possible routes to be implemented within a given facility;
* Defining test objective criteria or whether the test will cover individual structural elements or the entire test object;
* Based on the adopted criterion, the determination of a \(\mathbf{D}_{\mathbf{c}}\) target check set, which includes control and monitoring algorithms described in the criterion. This is the first stage of minimizing the check set by eliminating tests that do not provide any information on the studied configuration elements;
* Determination of a set of necessary checks, i.e., checks that must be executed, since they are the only ones that contain algorithms that can be verified using this test and no other test;
* Next, verification of whether the \(\mathbf{D}_{\mathbf{n}}\) set contains all control and monitoring algorithms, and if yes, execution of the tests without the need to minimize the objective function, since necessary checks are checks that have to be executed;
* If the \(\mathbf{D}_{\mathbf{n}}\) set does not contain all algorithms, it is required to determine and add \(\mathbf{D}_{\mathbf{n}\mathbf{d}}\) redundant checks that supplement the \(\mathbf{D}_{\mathbf{n}}\) set with additional tests;
* This is the stage where minimization criteria are defined. These include the test execution cost or the amount