I love how stupid this project is

si units and redefining speed metric as thrust/weight ratio

tests/test_units.py

@@ -0,0 +1,102 @@
+"""Tests for the unit-aware formatter."""
+
+from physcom.units import format_quantity
+
+
+class TestFormatQuantity:
+    def test_speed_km_h(self):
+        """33.33 m/s should display as ~120 km/h."""
+        result = format_quantity(33.33, "m/s")
+        assert "km/h" in result
+        assert "120" in result
+
+    def test_speed_km_s(self):
+        """10000 m/s should display as 10 km/s."""
+        result = format_quantity(10000, "m/s")
+        assert "km/s" in result
+
+    def test_distance_km(self):
+        """5000 m should display as 5 km."""
+        result = format_quantity(5000, "m")
+        assert "km" in result
+        assert "5" in result
+
+    def test_distance_ly(self):
+        """9.461e15 m should display as ~1 ly."""
+        result = format_quantity(9.461e15, "m")
+        assert "ly" in result
+
+    def test_distance_au(self):
+        """1.496e11 m should display as ~1 AU."""
+        result = format_quantity(1.496e11, "m")
+        assert "AU" in result
+
+    def test_mass_tons(self):
+        """5000 kg should display as 5 t."""
+        result = format_quantity(5000, "kg")
+        assert "t" in result
+
+    def test_mass_kg(self):
+        """50 kg should display as 50 kg."""
+        result = format_quantity(50, "kg")
+        assert "kg" in result
+
+    def test_energy_density_wh_kg(self):
+        """720000 J/kg should display as 200 Wh/kg."""
+        result = format_quantity(720000, "J/kg")
+        assert "Wh/kg" in result
+        assert "200" in result
+
+    def test_time_days(self):
+        """86400 s should display as 1 d."""
+        result = format_quantity(86400, "s")
+        assert "d" in result
+
+    def test_time_years(self):
+        """3.156e7 s should display as ~1 yr."""
+        result = format_quantity(3.156e7, "s")
+        assert "yr" in result
+
+    def test_cost_per_km(self):
+        """$/m always displays as $/km."""
+        result = format_quantity(0.001, "$/m")
+        assert "$/km" in result
+
+    def test_cost_per_ton_km(self):
+        """$/(kg·m) always displays as $/t·km."""
+        result = format_quantity(1e-6, "$/(kg\u00b7m)")
+        assert "$/t\u00b7km" in result
+
+    def test_emissions_g_per_km(self):
+        """kg/m always displays as g/km."""
+        result = format_quantity(1e-4, "kg/m")
+        assert "g/km" in result
+
+    def test_none_returns_dash(self):
+        assert format_quantity(None, "m/s") == "\u2014"
+
+    def test_dimensionless(self):
+        """0-1 unit should just return the number."""
+        result = format_quantity(0.75, "0-1")
+        assert result == "0.75"
+
+    def test_string_input(self):
+        """String values should be converted to float."""
+        result = format_quantity("5000", "m")
+        assert "km" in result
+
+    def test_non_numeric_string(self):
+        """Non-numeric string values returned as-is."""
+        assert format_quantity("true", "m") == "true"
+
+    def test_zero(self):
+        result = format_quantity(0, "m/s")
+        assert "m/s" in result
+
+    def test_area_m2(self):
+        result = format_quantity(50, "m\u00b2")
+        assert "m\u00b2" in result
+
+    def test_power_density(self):
+        result = format_quantity(5000, "W/kg")
+        assert "kW/kg" in result