testing stage; test phase
Refers to a phase in development or evaluation where something is being tested, such as a product, system, or process.
The new product is still in the testing stage.
Many problems were found during the test phase.
Similar meaning, but 試験段階 is slightly more formal and often used in technical or engineering contexts.
Compound of 試験 (test, examination) and 段階 (stage, phase).