     # The mock scan has one registration.
     mock =
       scan:
-        volumes: ({averageIntensity: 30 - Math.abs(10 - i)} for i in [1..32])
+        volumes:
+          images: ({averageIntensity: 30 - Math.abs(10 - i)} for i in [1..32])
         registrations: [
           {
             # Dampen the registration intensity a bit.
-            volumes: ({averageIntensity: 30 - Math.abs(10 - i) * 1.2} for i in [1..32])
+            volumes:
+              images: ({averageIntensity: 30 - Math.abs(10 - i) * 1.2} for i in [1..32])
           }
         ]
 

          .to.eql(expectedX)
        regY = (coord[1] for coord in regConfig.values)
        mockReg = mock.scan.registrations[0]
        expectedY = (vol.averageIntensity for vol in mockReg.volumes)
        expect(regY, "The registration Y coordinate is incorrect")
          .to.eql(expectedY)

        scanX = (coord[0] for coord in scanConfig.values)
        expect(scanX, "The scan X coordinate is incorrect")
          .to.eql(expectedX)
        expectedY = (img.averageIntensity for img in mock.scan.volumes.images)
        scanY = (coord[1] for coord in scanConfig.values)
        expect(scanY, "The scan Y coordinate is incorrect").to.eql(expectedY)

