custom unit tests for HTA models
using testthat custom expectations
https://testthat.r-lib.org/articles/custom-expectation.html
You don't have to understand all the code to know if works so you don't need to be an expert R programmer. Just like in industry, the quality of the code is determined by the testing. I think that all you need is to be sure that it passed a defined set of tests. This ideas has been started here [1] and here [5].
They make suggestions like:
- Life expectancy test sets
- the discount rate for QALYs to zero
- all dis-utilities to zero
- disease-specific mortality rates to the all-cause mortality rates.
- Quality-Adjusted Life Expectancy
- Total undiscounted intervention costs
- Changes in intervention cost
- Cohort size
- total remains constant
- number of patients in each health state in all cycles >=0.
- Sample PSA input means
Testing validity has been discussed in [3].
The collection of test are recorded in a document similar to this example.
Then these are translated to actual tests in the target language, such as the testthat packages examples here.
For tests using random numbers the same seed must be used.
[1]: Dasbach, E.J., Elbasha, E.H. Verification of Decision-Analytic Models for Health Economic Evaluations: An Overview. PharmacoEconomics 35, 673–683 (2017). https://doi.org/10.1007/s40273-017-0508-2
[2]: Alarid-Escudero, F., Krijkamp, E. M., Pechlivanoglou, P., Jalal, H., Kao, S. Y. Z., Yang, A., & Enns, E. A. (2019). A Need for Change! A Coding Framework for Improving Transparency in Decision Modeling. PharmacoEconomics, 37(11), 1329–1339. https://doi.org/10.1007/s40273-019-00837-x
[3]: McCabe, C., & Dixon, S. (2000). Testing the validity of cost-effectiveness models. PharmacoEconomics, 17(5), 501–513. https://doi.org/10.2165/00019053-200017050-00007
[4]: Husereau, D., Drummond, M., Petrou, S., Carswell, C., Moher, D., Greenberg, D., … Loder, E. (2013). Consolidated Health Economic Evaluation Reporting Standards (CHEERS) statement. European Journal of Health Economics, 14(3), 367–372. https://doi.org/10.1007/s10198-013-0471-6
[5] Tappenden, P., Chilcott, J.B. Avoiding and Identifying Errors and Other Threats to the Credibility of Health Economic Models. PharmacoEconomics 32, 967–979 (2014). https://doi.org/10.1007/s40273-014-0186-2