### Question:
ComplexMathUtils { public static ComplexNumber conjugate(ComplexNumber z) { ArgChecker.notNull(z, "z"); return new ComplexNumber(z.getReal(), -z.getImaginary()); } private  ComplexMathUtils(); static ComplexNumber add(ComplexNumber z1, ComplexNumber z2); static ComplexNumber add(ComplexNumber... z); static ComplexNumber add(ComplexNumber z, double x); static ComplexNumber add(double x, ComplexNumber z); static double arg(ComplexNumber z); static ComplexNumber conjugate(ComplexNumber z); static ComplexNumber divide(ComplexNumber z1, ComplexNumber z2); static ComplexNumber divide(ComplexNumber z, double x); static ComplexNumber divide(double x, ComplexNumber z); static ComplexNumber exp(ComplexNumber z); static ComplexNumber inverse(ComplexNumber z); static ComplexNumber log(ComplexNumber z); static double mod(ComplexNumber z); static ComplexNumber square(ComplexNumber z); static ComplexNumber multiply(ComplexNumber z1, ComplexNumber z2); static ComplexNumber multiply(ComplexNumber... z); static ComplexNumber multiply(double x, ComplexNumber... z); static ComplexNumber multiply(ComplexNumber z, double x); static ComplexNumber multiply(double x, ComplexNumber z); static ComplexNumber pow(ComplexNumber z1, ComplexNumber z2); static ComplexNumber pow(ComplexNumber z, double x); static ComplexNumber pow(double x, ComplexNumber z); static ComplexNumber sqrt(ComplexNumber z); static ComplexNumber subtract(ComplexNumber z1, ComplexNumber z2); static ComplexNumber subtract(ComplexNumber z, double x); static ComplexNumber subtract(double x, ComplexNumber z);  }### Answer:
@Test public void testConjugate() { assertComplexEquals(ComplexMathUtils.conjugate(ComplexMathUtils.conjugate(Z1)), Z1); }