Electrified vehicle drivetrains mainly use three motor types: induction machines, permanently excited synchronous machines, and externally excited synchronous machines (EESM). The latter offers advantages specifically for passenger car applications. It also doesn’t need permanent magnets. A key technical challenge of EESMs is supplying current to the rotating rotor windings, traditionally achieved using slip rings and brushes. MAHLE’s Contactless Transmitter (MCT) provides a wear free alternative, avoiding friction, brush wear, and contamination. Functional validation of the MCT is performed at MAHLE’s e mobility test facility across multiple system integration levels. Signal level hardware in the loop benches allow early testing of rotor current control algorithms before target hardware exists. Higher integration levels are addressed through component and subsystem test benches, and final validation occurs on the electric motor test bench. Functional validation of the MCT is performed at MAHLE’s e mobility test facility across multiple system integration levels. Signal level hardware in the loop benches allow early testing of rotor current control algorithms before target hardware exists. Higher integration levels are addressed through component and subsystem test benches, and final validation occurs on the electric motor test bench. Development speed is significantly improved by this multi stage approach through parallelization. It also enables focused root cause analysis by isolating deviations to specific interfaces. Consistency of models and test cases across all test environments is essential. To ensure comparability, all test benches access a centralized model library — the Digital Model Master — which provides uniform functional parameters for residual system simulation. Additionally, automated test execution ensures that discrepancies between integration levels are caused by interface changes, not procedural differences. The paper presents the novel methodology, describes the testing infrastructure used and highlights for the first time results at component and subsystem levels.