After measuring the swing speed of a hydraulic shovel during a test, the operator began rotating the bucket to the right to measure the swirl flow. The operator suddenly realized that the other tester, who had become preoccupied with the swing speed measurements, had inadvertently stepped into the turning radius of the shovel. He tried to avoid hitting the other tester by turning the shovel in the other direction, but could not change direction in time. The tester was hit by the bucket.