               expect(wave.frequency) ≈ ($0.frequency, 0.1)
               expect(wave.wavelength) ≈ ($0.wavelength, 0.01)
               expect(wave.period) ≈ ($0.period, 0.01)
+
+              for (index, value) in wave.harmonics.enumerate() {
+                expect(value.frequency) ≈ (Double(index + 1) * $0.frequency, 1)
+              }
             }
           }
         }

              expect(wave.frequency) ≈ ($0.frequency, 0.1)
              expect(wave.wavelength) ≈ ($0.wavelength, 0.01)
              expect(wave.period) ≈ ($0.period, 0.01)
            }
          }
        }

              expect(wave.frequency) ≈ ($0.frequency, 0.01)
              expect(wave.wavelength) ≈ ($0.wavelength, 0.01)
              expect(wave.period) ≈ ($0.period, 0.01)

              for (index, value) in wave.harmonics.enumerate() {
                expect(value.frequency) ≈ (Double(index + 1) * $0.frequency, 0.01)
              }
            }
          }
        }
