i.evapo.mh: add test file (#5519)

* add test file

* modify docstrings and make edits

* modify existing test to fail because of bug

* changed the stats after bug fix

Author: jayneel-shah18

imagery/i.evapo.mh/testsuite/test_i_evapo_mh.py

@@ -0,0 +1,193 @@
+import grass.script as gs
+from grass.gunittest.case import TestCase
+from grass.gunittest.main import test
+import math
+
+
+class TestEvapotranspirationMH(TestCase):
+    """Regression tests for i.evapo.mh module"""
+
+    tmp_rasters = []
+    netradiation_diurnal = "netrad"
+    average_temperature = "avg_temp"
+    minimum_temperature = "min_temp"
+    maximum_temperature = "max_temp"
+    precipitation = "precipitation"
+    output_map = "et_output"
+
+    @classmethod
+    def setUpClass(cls):
+        """Setup input rasters and configure test environment."""
+        seed = 43
+        cls.use_temp_region()
+        gs.run_command("g.region", n=10, s=0, e=10, w=0, rows=10, cols=10)
+        cls.runModule(
+            "r.mapcalc",
+            expression=f"{cls.netradiation_diurnal} = rand(0, 160)",
+            seed=seed,
+            overwrite=True,
+        )
+        cls.runModule(
+            "r.mapcalc",
+            expression=f"{cls.minimum_temperature} = rand(0, 15)",
+            seed=seed,
+            overwrite=True,
+        )
+        cls.runModule(
+            "r.mapcalc",
+            expression=f"{cls.maximum_temperature} = rand(25, 40)",
+            seed=seed,
+            overwrite=True,
+        )
+        cls.runModule(
+            "r.mapcalc",
+            expression=f"{cls.average_temperature} = ({cls.minimum_temperature}+{cls.maximum_temperature})/2",
+            overwrite=True,
+        )
+        cls.runModule(
+            "r.mapcalc",
+            expression=f"{cls.precipitation} = rand(50, 130)",
+            seed=seed,
+            overwrite=True,
+        )
+        cls.tmp_rasters.extend(
+            [
+                cls.netradiation_diurnal,
+                cls.average_temperature,
+                cls.minimum_temperature,
+                cls.maximum_temperature,
+                cls.precipitation,
+            ]
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        """Remove generated rasters and reset test environment."""
+        gs.run_command("g.remove", type="raster", name=cls.tmp_rasters, flags="f")
+        cls.del_temp_region()
+
+    def create_raster(self, name, expression, seed=None):
+        """Create temporary raster map and register it for cleanup."""
+        self.runModule(
+            "r.mapcalc",
+            expression=f"{name} = {expression}",
+            seed=seed,
+            overwrite=True,
+        )
+        self.tmp_rasters.append(name)
+
+    def run_evapo(self, output, flags="", overwrite=True, **kwargs):
+        """Execute the i.evapo.mh module with standardized parameters."""
+        self.assertModule(
+            "i.evapo.mh",
+            flags=flags,
+            output=output,
+            overwrite=overwrite,
+            **kwargs,
+        )
+        self.tmp_rasters.append(output)
+
+    def test_z_flag_negative_values(self):
+        """Verify -z flag clamps negative output values to zero."""
+        self.create_raster("netrad_z", "10")
+        self.create_raster("min_temp_z", "0")
+        self.create_raster("max_temp_z", "10")
+        self.create_raster("avg_temp_z", "(min_temp_z + max_temp_z)/2")
+
+        self.run_evapo(
+            flags="z",
+            netradiation_diurnal="netrad_z",
+            average_temperature="avg_temp_z",
+            minimum_temperature="min_temp_z",
+            maximum_temperature="max_temp_z",
+            precipitation=self.precipitation,
+            output=self.output_map,
+        )
+        stats = gs.parse_command(
+            "r.univar", map=self.output_map, flags="g", format="json"
+        )[0]
+        self.assertGreaterEqual(stats["min"], 0)
+
+    def test_h_flag_precipitation_ignored(self):
+        """Confirm -h flag makes precipitation input irrelevant."""
+        self.run_evapo(
+            flags="h",
+            netradiation_diurnal=self.netradiation_diurnal,
+            average_temperature=self.average_temperature,
+            minimum_temperature=self.minimum_temperature,
+            maximum_temperature=self.maximum_temperature,
+            precipitation=self.precipitation,
+            output=f"{self.output_map}_h",
+        )
+        self.run_evapo(
+            flags="h",
+            netradiation_diurnal=self.netradiation_diurnal,
+            average_temperature=self.average_temperature,
+            minimum_temperature=self.minimum_temperature,
+            maximum_temperature=self.maximum_temperature,
+            output=f"{self.output_map}_h_noprecip",
+        )
+        self.assertRastersNoDifference(
+            f"{self.output_map}_h",
+            f"{self.output_map}_h_noprecip",
+            precision=1e-6,
+        )
+
+    def test_s_flag_different_output(self):
+        """Check -s flag produces different results from default method."""
+        self.run_evapo(
+            netradiation_diurnal=self.netradiation_diurnal,
+            average_temperature=self.average_temperature,
+            minimum_temperature=self.minimum_temperature,
+            maximum_temperature=self.maximum_temperature,
+            precipitation=self.precipitation,
+            output=f"{self.output_map}_default",
+        )
+        self.run_evapo(
+            flags="s",
+            netradiation_diurnal=self.netradiation_diurnal,
+            average_temperature=self.average_temperature,
+            minimum_temperature=self.minimum_temperature,
+            maximum_temperature=self.maximum_temperature,
+            precipitation=self.precipitation,
+            output=f"{self.output_map}_s",
+        )
+        self.create_raster(
+            "diff_map", f"{self.output_map}_default - {self.output_map}_s"
+        )
+        stats = {"min": 0, "max": 2.276227, "mean": 0.985087}
+        self.assertRasterFitsUnivar(raster="diff_map", reference=stats, precision=1e-6)
+
+    def test_hargreaves_formula(self):
+        """Validate Hargreaves formula implementation matches reference."""
+        self.create_raster("netrad_test", "0.1446759")
+        self.create_raster("tmin_test", "10")
+        self.create_raster("tmax_test", "30")
+        self.create_raster("tavg_test", "20")
+
+        ra_input_w = 0.1446759
+        tmin = 10
+        tmax = 30
+        tavg = 20
+
+        ra_mj = ra_input_w * 0.0864
+        td = tmax - tmin
+
+        expected_et = 0.0023 * 0.408 * ra_mj * (tavg + 17.8) * math.sqrt(td)
+
+        self.run_evapo(
+            flags="h",
+            netradiation_diurnal="netrad_test",
+            average_temperature="tavg_test",
+            minimum_temperature="tmin_test",
+            maximum_temperature="tmax_test",
+            output="et_const",
+        )
+        stats = gs.parse_command("r.univar", map="et_const", flags="g", format="json")[
+            0
+        ]
+        self.assertAlmostEqual(stats["mean"], expected_et)
+
+
+if __name__ == "__main__":
+    test()