Grid-forming battery energy storage systems (GFM-BESS) are crucial for enhancing grid stability and enabling black start capabilities. This study examines the black start performance and fault response of a GFM-BESS within a Wind-BESS hybrid power plant through multi-scenario field tests. The first phase validates the soft start-up capability on a 35kV bus, achieving voltage buildup within 10 seconds, with steady-state voltage maintained at 1.06–1.08 p.u. and frequency deviation within ±0.2 Hz. The second phase demonstrates plant-level black start and load operation, where the GFM-BESS sustains bus voltage between 0.9–1.0 p.u., with transient peaks under 1.35 p.u. during transformer switching or line energization, and transient durations below 7 ms. The third phase involves a three-phase short-circuit test: during a 250-ms fault, terminal voltage drops to 0.3 p.u. with a peak fault current of 2.97 p.u., followed by rapid recovery. Results confirm the exceptional voltage and frequency regulation, transient stability, and fault resilience of GFM-BESS, providing vital insights for improving grid reliability in systems with high inverter-based resource penetration.