Add unittesting

[adeeconometrics]

Function	Forward Mode	Reverse Mode	Scalar	Vector	Matrix
arithmetic	- [x]	- [x]	- [x]	- [ ]	- [ ]
exp	- [x]	- [x]	- [x]	- [ ]	- [ ]
pow	- [x]	- [x]	- [x]	- [ ]	- [ ]
ln	- [x]	- [x]	- [x]	- [ ]	- [ ]
sin	- [x]	- [x]	- [x]	- [ ]	- [ ]
cos	- [x]	- [x]	- [x]	- [ ]	- [ ]
tan	- [x]	- [x]	- [x]	- [ ]	- [ ]
cot	- [x]	- [x]	- [x]	- [ ]	- [ ]
sec	- [x]	- [x]	- [x]	- [ ]	- [ ]
csc	- [x]	- [x]	- [x]	- [ ]	- [ ]
asin	- [x]	- [x]	- [x]	- [ ]	- [ ]
acos	- [x]	- [x]	- [x]	- [ ]	- [ ]
atan	- [x]	- [x]	- [x]	- [ ]	- [ ]
acot	- [x]	- [x]	- [x]	- [ ]	- [ ]
asec	- [x]	- [x]	- [x]	- [ ]	- [ ]
acsc	- [x]	- [x]	- [x]	- [ ]	- [ ]
sinh	- [x]	- [x]	- [x]	- [ ]	- [ ]
cosh	- [x]	- [x]	- [x]	- [ ]	- [ ]
tanh	- [x]	- [x]	- [x]	- [ ]	- [ ]
coth	- [x]	- [x]	- [x]	- [ ]	- [ ]
sech	- [x]	- [x]	- [x]	- [ ]	- [ ]
csch	- [x]	- [x]	- [x]	- [ ]	- [ ]
asinh	- [x]	- [x]	- [x]	- [ ]	- [ ]
acosh	- [x]	- [x]	- [x]	- [ ]	- [ ]
atanh	- [x]	- [x]	- [x]	- [ ]	- [ ]
acoth	- [x]	- [x]	- [x]	- [ ]	- [ ]
asech	- [x]	- [x]	- [x]	- [ ]	- [ ]
acsch	- [x]	- [x]	- [x]	- [ ]	- [ ]

[adeeconometrics]

Review for handling domain errors in inverse and inverse hyperbolic derivative rules

• [ ] asin and asinh
• [ ] acos and acosh
• [ ] asec and asech
• [ ] atan and atanh
• [ ] acot and acoth
• [ ] acsc and acsch

Example:

// WARNING: Domain error should be handled in the future
TEST(RSymbol, AcscScalar) {
  ad::RSym a{0.5}; // should include multivariate tests

  auto c = acsc(a);

  const auto df_c = ad::gradient(c);

  EXPECT_DOUBLE_EQ(c.value(), 1.0 / std::asin(0.5));
  EXPECT_DOUBLE_EQ(df_c.at(a),
                   -1.0 / (std::sqrt(1 - std::pow(0.5, 2)) * std::abs(0.5)));
}