Address review feedback in coverage tests

Agent-Logs-Url: https://github.com/astomodynamics/cddp-cpp/sessions/74fc7104-f2ef-41e6-b9dc-7425d8765f3b

Co-authored-by: astomodynamics <49183997+astomodynamics@users.noreply.github.com>

Author: Copilot

tests/cddp_core/test_finite_difference.cpp

@@ -21,6 +21,10 @@
 
 namespace {
 
+constexpr int kCentralDifference = 0;
+constexpr int kForwardDifference = 1;
+constexpr int kBackwardDifference = 2;
+
 double quadratic_cost(const Eigen::VectorXd &x) {
   return x(0) * x(0) + 3.0 * x(0) * x(1) + std::sin(x(1));
 }
@@ -55,7 +59,9 @@ TEST(FiniteDifferenceTest, GradientMatchesAnalyticForAllModes) {
   const Eigen::Vector2d x(0.4, -0.2);
   const Eigen::Vector2d grad_expected = expected_gradient(x);
 
-  for (const int mode : std::array<int, 3>{0, 1, 2}) {
+  for (const int mode :
+       std::array<int, 3>{kCentralDifference, kForwardDifference,
+                          kBackwardDifference}) {
     const Eigen::VectorXd grad =
         cddp::finite_difference_gradient(quadratic_cost, x, 1e-6, mode);
     EXPECT_TRUE(grad.isApprox(grad_expected, 1e-4)) << "mode=" << mode;
@@ -66,7 +72,9 @@ TEST(FiniteDifferenceTest, JacobianMatchesAnalyticForAllModes) {
   const Eigen::Vector2d x(-0.3, 0.6);
   const Eigen::Matrix2d jac_expected = expected_jacobian(x);
 
-  for (const int mode : std::array<int, 3>{0, 1, 2}) {
+  for (const int mode :
+       std::array<int, 3>{kCentralDifference, kForwardDifference,
+                          kBackwardDifference}) {
     const Eigen::MatrixXd jac =
         cddp::finite_difference_jacobian(vector_function, x, 1e-6, mode);
     EXPECT_TRUE(jac.isApprox(jac_expected, 1e-4)) << "mode=" << mode;
@@ -77,7 +85,9 @@ TEST(FiniteDifferenceTest, HessianMatchesAnalyticForAllModes) {
   const Eigen::Vector2d x(0.4, -0.2);
   const Eigen::Matrix2d hess_expected = expected_hessian(x);
 
-  for (const int mode : std::array<int, 3>{0, 1, 2}) {
+  for (const int mode :
+       std::array<int, 3>{kCentralDifference, kForwardDifference,
+                          kBackwardDifference}) {
     const Eigen::MatrixXd hess =
         cddp::finite_difference_hessian(quadratic_cost, x, 1e-5, mode);
     EXPECT_TRUE(hess.isApprox(hess_expected, 2e-2)) << "mode=" << mode;

tests/cddp_core/test_helper_conversions.cpp

@@ -31,14 +31,14 @@ TEST(HelperConversionTest, EulerRotationRoundTripIsConsistent) {
 }
 
 TEST(HelperConversionTest, RotationMatrixToEulerHandlesGimbalLock) {
-  const double half_pi = std::acos(-1.0) / 2.0;
-  const Eigen::Vector3d euler(0.5, half_pi, -0.2);
+  constexpr double kHalfPi = 1.5707963267948966;
+  const Eigen::Vector3d euler(0.5, kHalfPi, -0.2);
 
   const Eigen::Matrix3d rotation = cddp::helper::eulerZYXToRotationMatrix(euler);
   const Eigen::Vector3d recovered = cddp::helper::rotationMatrixToEulerZYX(rotation);
 
   EXPECT_TRUE(recovered.allFinite());
-  EXPECT_NEAR(recovered(1), half_pi, 1e-9);
+  EXPECT_NEAR(recovered(1), kHalfPi, 1e-9);
   EXPECT_NEAR(recovered(2), 0.0, 1e-12);
 }