# tests/cryo_tank/test_properties.py
"""Tests for CoolProp property wrappers."""
import pytest
import sys
sys.path.insert(0, "src")

from cryo_tank.properties import (
    ln2_rho, ln2_h, ln2_u, ln2_T_from_u,
    n2_vapor_u, n2_sat_pressure,
    he_u, he_h, he_cp, he_cv,
)
from cryo_tank.config import P_WORKING


class TestLN2Properties:
    """Liquid nitrogen properties at P = 0.17 MPa."""

    def test_ln2_density_at_78K(self):
        rho = ln2_rho(78.0, P_WORKING)
        assert 800 < rho < 810  # ~803 kg/m3

    def test_ln2_enthalpy_at_77K(self):
        h = ln2_h(77.0, P_WORKING)
        assert -130000 < h < -110000  # ~-122695 J/kg

    def test_ln2_internal_energy_at_78K(self):
        u = ln2_u(78.0, P_WORKING)
        assert -130000 < u < -110000  # ~-120865 J/kg

    def test_ln2_T_from_u_roundtrip(self):
        T_orig = 78.0
        u = ln2_u(T_orig, P_WORKING)
        T_recovered = ln2_T_from_u(u, P_WORKING)
        assert abs(T_recovered - T_orig) < 0.01


class TestN2VaporProperties:
    """N2 vapor properties."""

    def test_n2_sat_pressure_at_78K(self):
        P_sat = n2_sat_pressure(78.0)
        assert 0.10e6 < P_sat < 0.12e6  # ~0.1093 MPa

    def test_n2_vapor_internal_energy_at_78K(self):
        u = n2_vapor_u(78.0)
        assert 50000 < u < 60000  # ~55547 J/kg


class TestHeliumProperties:
    """Helium (ideal gas) properties."""

    def test_he_cp_near_5196(self):
        cp = he_cp()
        assert abs(cp - 5196.2) < 10  # monatomic ideal gas

    def test_he_cv_near_3117(self):
        cv = he_cv()
        assert abs(cv - 3117.1) < 10

    def test_he_enthalpy_at_100K(self):
        h = he_h(100.0)
        # CoolProp gives ~524762 J/kg at 100K
        assert 500000 < h < 550000

    def test_he_internal_energy_at_78K(self):
        u = he_u(78.0)
        assert 200000 < u < 280000  # ~247932 J/kg