TestGSLIntegration.cpp

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#include <gtest/gtest.h>
#include <cmath>
#include "Utilities/GSLIntegration.h"
 
class GSLIntegrationTest : public ::testing::Test {
protected:
    void SetUp() override {
        // Test setup
    }
};
 
// Test function: f(x) = x
double linear_func(double x, void* /* params */) { return x; }
 
// Test function: f(x) = x^2
double quadratic_func(double x, void* /* params */) { return x * x; }
 
// Test function: f(x) = sin(x)
double sin_func(double x, void* /* params */) { return std::sin(x); }
 
// Test function: f(x) = exp(x)
double exp_func(double x, void* /* params */) { return std::exp(x); }
 
TEST_F(GSLIntegrationTest, LinearFunction) {
    gsl_function F;
    F.function = linear_func;
    F.params   = nullptr;
 
    gsl_integration_workspace* w = gsl_integration_workspace_alloc(1000);
 
    double result, error;
    int status = gsl_integration_qag(
            &F, 0.0, 1.0, 1e-10, 1e-10, 1000, GSL_INTEG_GAUSS15, w, &result, &error);
 
    EXPECT_EQ(status, 0);
    EXPECT_NEAR(result, 0.5, 1e-6);  // ∫x dx from 0 to 1 = 0.5
 
    gsl_integration_workspace_free(w);
}
 
TEST_F(GSLIntegrationTest, QuadraticFunction) {
    gsl_function F;
    F.function = quadratic_func;
    F.params   = nullptr;
 
    gsl_integration_workspace* w = gsl_integration_workspace_alloc(1000);
 
    double result, error;
    int status = gsl_integration_qag(
            &F, 0.0, 2.0, 1e-10, 1e-10, 1000, GSL_INTEG_GAUSS15, w, &result, &error);
 
    EXPECT_EQ(status, 0);
    EXPECT_NEAR(result, 8.0 / 3.0, 1e-6);  // ∫x^2 dx from 0 to 2 = 8/3
 
    gsl_integration_workspace_free(w);
}
 
TEST_F(GSLIntegrationTest, SinFunction) {
    gsl_function F;
    F.function = sin_func;
    F.params   = nullptr;
 
    gsl_integration_workspace* w = gsl_integration_workspace_alloc(1000);
 
    double result, error;
    int status = gsl_integration_qag(
            &F, 0.0, M_PI, 1e-10, 1e-10, 1000, GSL_INTEG_GAUSS15, w, &result, &error);
 
    EXPECT_EQ(status, 0);
    EXPECT_NEAR(result, 2.0, 1e-6);  // ∫sin(x) dx from 0 to π = 2
 
    gsl_integration_workspace_free(w);
}
 
TEST_F(GSLIntegrationTest, ExpFunction) {
    gsl_function F;
    F.function = exp_func;
    F.params   = nullptr;
 
    gsl_integration_workspace* w = gsl_integration_workspace_alloc(1000);
 
    double result, error;
    int status = gsl_integration_qag(
            &F, 0.0, 1.0, 1e-10, 1e-10, 1000, GSL_INTEG_GAUSS15, w, &result, &error);
 
    EXPECT_EQ(status, 0);
    EXPECT_NEAR(result, std::exp(1.0) - 1.0, 1e-6);  // ∫e^x dx from 0 to 1 = e - 1
 
    gsl_integration_workspace_free(w);
}
 
TEST_F(GSLIntegrationTest, NegativeRange) {
    gsl_function F;
    F.function = linear_func;
    F.params   = nullptr;
 
    gsl_integration_workspace* w = gsl_integration_workspace_alloc(1000);
 
    double result, error;
    int status = gsl_integration_qag(
            &F, -1.0, 1.0, 1e-10, 1e-10, 1000, GSL_INTEG_GAUSS15, w, &result, &error);
 
    EXPECT_EQ(status, 0);
    EXPECT_NEAR(result, 0.0, 1e-6);  // ∫x dx from -1 to 1 = 0
 
    gsl_integration_workspace_free(w);
}
 
TEST_F(GSLIntegrationTest, SmallRange) {
    gsl_function F;
    F.function = quadratic_func;
    F.params   = nullptr;
 
    gsl_integration_workspace* w = gsl_integration_workspace_alloc(1000);
 
    double result, error;
    int status = gsl_integration_qag(
            &F, 0.0, 0.1, 1e-10, 1e-10, 1000, GSL_INTEG_GAUSS15, w, &result, &error);
 
    EXPECT_EQ(status, 0);
    EXPECT_NEAR(result, 0.1 * 0.1 * 0.1 / 3.0, 1e-6);
 
    gsl_integration_workspace_free(w);
}