ENH: first version of tests for 3dof rocketpy

- ENH: added first versions of tests using python assert statements for pointmassmotor, pointmassrocket and 3dof segments of flight.

Author: aZira371

tests/unit/motors/test_point_mass_motor.py

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+import pytest
+from rocketpy.motors.point_mass_motor import PointMassMotor
+
+def test_init_required_args():
+    m = PointMassMotor(thrust_source=10, dry_mass=1.0, propellant_initial_mass=0.5, burn_time=1.2)
+    assert isinstance(m, PointMassMotor)
+    assert m.dry_mass == 1.0
+    assert m.propellant_initial_mass == 0.5
+
+def test_missing_required_args_raises():
+    with pytest.raises(ValueError):
+        PointMassMotor(10, 1.0, None, 1)
+    with pytest.raises(ValueError):
+        PointMassMotor(10, 1.0, 1.2)
+    with pytest.raises(TypeError):
+        PointMassMotor([], 1.0, 1.2, 1)
+
+def test_exhaustvelocity_and_totalmassflowrate():
+    m = PointMassMotor(thrust_source=10, dry_mass=1.0, propellant_initial_mass=1.0, burn_time=2.0)
+    ev_func = m.exhaustvelocity()
+    assert hasattr(ev_func, 'getValue')
+    tmf_func = m.totalmassflowrate
+    assert hasattr(tmf_func, 'getValue')
+
+def test_zero_inertias():
+    m = PointMassMotor(thrust_source=10, dry_mass=1.0, propellant_initial_mass=1.0, burn_time=2.0)
+    assert m.propellantI11().getValue(0) == 0
+    assert m.propellantI22().getValue(0) == 0
+    assert m.propellantI33().getValue(0) == 0
+
+def test_callable_thrust():
+    m = PointMassMotor(thrust_source=lambda t: 100*t, dry_mass=2, propellant_initial_mass=2, burn_time=4)
+    assert m.thrust_source(0.5) == 50

tests/unit/rocket/test_point_mass_rocket.py

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+from rocketpy.rocket.rocket import PointMassRocket
+from rocketpy.motors.point_mass_motor import PointMassMotor
+
+def test_point_mass_rocket_basic_properties():
+    motor = PointMassMotor(10, 1.0, 0.5, 1.0)
+    rocket = PointMassRocket(
+        radius=0.05,
+        mass=2.0,
+        center_of_mass_without_motor=0.1,
+        power_off_drag=0.7,
+        power_on_drag=0.8
+    )
+    rocket.addmotor(motor, 0)
+    assert rocket.radius == 0.05
+    assert rocket.mass == 2.0
+    assert rocket.motor is motor
+    assert rocket.dryI11 == 0.0  # 3-DOF: inertias are forced zero
+
+def test_structural_and_total_mass():
+    """Test structural and total mass properties of point mass rocket."""
+    motor = PointMassMotor(10, 1.0, 1.1, 2.0)
+    rocket = PointMassRocket(
+        radius=0.03,
+        mass=2.5,
+        center_of_mass_without_motor=0,
+        power_off_drag=0.3,
+        power_on_drag=0.4
+    )
+    rocket.addmotor(motor, 0)
+    
+    # Test that structural mass and total mass are calculated correctly
+    assert rocket.mass == 2.5
+    expected_total_mass = rocket.mass + motor.propellant_initial_mass
+    assert abs(rocket.total_mass(0) - expected_total_mass) < 1e-6
+
+def test_add_motor_overwrites():
+    """Test that adding a motor overwrites the previous motor."""
+    motor1 = PointMassMotor(10, 1, 1.1, 2.0)
+    motor2 = PointMassMotor(20, 2, 1.5, 3.0)
+    rocket = PointMassRocket(0.02, 1.0, 0.0, 0.2, 0.5)
+    rocket.addmotor(motor1, position=0)
+    rocket.addmotor(motor2, position=0)
+    assert rocket.motor == motor2

tests/unit/simulation/test_flight_3dof.py

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+import pytest
+import numpy as np
+from rocketpy.simulation.flight import Flight
+from rocketpy.rocket.rocket import PointMassRocket
+from rocketpy.motors.point_mass_motor import PointMassMotor
+
+class DummyEnv:
+    # Minimal stub, adapt with real Environment in your RocketPy setup
+    windvelocityx = windvelocityy = speedofsound = pressure = density = dynamicviscosity = lambda self: 0
+    gravity = lambda self: 9.81
+    elevation = 0
+    def __getattr__(self, name):
+        return lambda *a, **k: 0
+
+def make_simple_3dof_components():
+    env = DummyEnv()
+    motor = PointMassMotor(10, dry_mass=1.0, propellant_initial_mass=0.5, burn_time=2.2)
+    rocket = PointMassRocket(0.05, 2.0, 0.1, 0.5, 0.6)
+    rocket.addmotor(motor, 0)
+    return env, rocket
+
+def test_3dof_simulation_mode_autoset():
+    env, rocket = make_simple_3dof_components()
+    flight = Flight(rocket=rocket, environment=env, rail_length=1, simulation_mode="3 DOF")
+    assert flight.simulation_mode == "3 DOF"
+
+def test_3dof_simulation_mode_warning(monkeypatch):
+    env, rocket = make_simple_3dof_components()
+    monkeypatch.setattr("warnings.warn", lambda *a, **k: None)
+    f = Flight(rocket=rocket, environment=env, rail_length=1, simulation_mode="6 DOF")
+    assert f.simulation_mode == "3 DOF"
+
+def test_3dof_equations_of_motion_functions():
+    env, rocket = make_simple_3dof_components()
+    flight = Flight(rocket=rocket, environment=env, rail_length=1, simulation_mode="3 DOF")
+    u = [0]*13  # Proper size for generalized state for 3/6 DOF probably
+    result = flight.udotgeneralized3dof(0, u)
+    assert isinstance(result, list) or isinstance(result, np.ndarray)
+
+def test_invalid_simulation_mode():
+    env, rocket = make_simple_3dof_components()
+    with pytest.raises(ValueError):
+        Flight(rocket=rocket, environment=env, rail_length=1, simulation_mode="2 DOF")