### Question:
AddFixedCurve implements Curve, ImmutableBean, Serializable { public static AddFixedCurve of(Curve fixedCurve, Curve spreadCurve) { return new AddFixedCurve(fixedCurve, spreadCurve); } private  AddFixedCurve(
      Curve fixedCurve,
      Curve spreadCurve); static AddFixedCurve of(Curve fixedCurve, Curve spreadCurve); @Override CurveMetadata getMetadata(); @Override AddFixedCurve withMetadata(CurveMetadata metadata); @Override int getParameterCount(); @Override double getParameter(int parameterIndex); @Override ParameterMetadata getParameterMetadata(int parameterIndex); @Override AddFixedCurve withParameter(int parameterIndex, double newValue); @Override AddFixedCurve withPerturbation(ParameterPerturbation perturbation); @Override double yValue(double x); @Override UnitParameterSensitivity yValueParameterSensitivity(double x); @Override double firstDerivative(double x); @Override ImmutableList<Curve> split(); @Override AddFixedCurve withUnderlyingCurve(int curveIndex, Curve curve); static AddFixedCurve.Meta meta(); @Override AddFixedCurve.Meta metaBean(); Curve getFixedCurve(); Curve getSpreadCurve(); @Override boolean equals(Object obj); @Override int hashCode(); @Override String toString();  }### Answer:
@Test public void test_invalid() { assertThatIllegalArgumentException() .isThrownBy(() -> AddFixedCurve.of(null, SPREAD_CURVE)); assertThatIllegalArgumentException() .isThrownBy(() -> AddFixedCurve.of(FIXED_CURVE, null)); }
@Test public void coverage() { coverImmutableBean(ADD_FIXED_CURVE); coverBeanEquals(ADD_FIXED_CURVE, AddFixedCurve.of(SPREAD_CURVE, FIXED_CURVE)); }