let sys = DenseSystem(test_params...),
    beta = 12.34,
    P = 256,
    sampling_sys = DiagonalSystem(test_params_sampling...)

    @test isapprox(ground_pes(sys, (-1.0, 2.0, -3.0, 4.0); lengths=(2, 3)), [11.73057536 14.61381238; -1.50969268 1.59347336; 22.29332112 25.61509171])

    @test isapprox(path_mean_std(sampling_sys, beta, P, 1, 1), 0.201370345)
    @test isapprox(path_mean_std(sampling_sys, beta, P, test_S_sampling, test_M), 0.108103579)
end
