r.buffer: Added test script (OSGeo#4482)

* Added test script for r.buffer

* Corrected input map and added tearDown method to delete temp maps

* Added pre commit fixes

* Added resolution for feedback

* Tweaked the last test and used f string

* Update raster/r.buffer/testsuite/test_buffer.py

Reduced the region of the test

Co-authored-by: Anna Petrasova <[email protected]>

* Corrected redudancy

* Streamlined output map initialization

---------

Co-authored-by: Anna Petrasova <[email protected]>

raster/r.buffer/testsuite/test_buffer.py

@@ -0,0 +1,99 @@
+from grass.gunittest.case import TestCase
+from grass.gunittest.main import test
+from grass.gunittest.gmodules import SimpleModule
+import grass.script as gs
+
+
+class TestRBuffer(TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        """Set up a temporary region for testing."""
+        cls.output = "test_buffer"
+        cls.use_temp_region()
+        cls.runModule("g.region", n=223000, s=220000, w=640000, e=643000, nsres=100)
+
+    @classmethod
+    def tearDownClass(cls):
+        """Clean up after tests."""
+        cls.del_temp_region()
+
+    def tearDown(self):
+        """Remove temporary maps created during tests"""
+        gs.run_command(
+            "g.remove",
+            type="raster",
+            name="test_buffer,zero_map,null_map",
+            flags="f",
+        )
+
+    def test_buffer_creation(self):
+        """Test creating a buffer around roadsmajor with multiple distances."""
+        distances = [100, 200, 300, 400, 500]
+
+        module = SimpleModule(
+            "r.buffer",
+            input="roadsmajor",
+            output=self.output,
+            distances=distances,
+            overwrite=True,
+        )
+        self.assertModule(module)
+
+        self.assertRasterExists(self.output)
+
+        expected_categories = [i + 1 for i in range(len(distances) + 1)]
+
+        self.assertRasterMinMax(
+            map=self.output,
+            refmin=min(expected_categories),
+            refmax=max(expected_categories),
+            msg=f"Buffer zones should have category values from 1 to {max(expected_categories)}",
+        )
+
+    def test_no_non_null_values(self):
+        """Test r.buffer with null input raster resulting in an empty output."""
+        null_map = "null_map"
+        self.runModule("r.mapcalc", expression=f"{null_map} = null()")
+
+        distances = [100, 200, 300]
+
+        module = SimpleModule(
+            "r.buffer",
+            input=null_map,
+            output=self.output,
+            distances=distances,
+            overwrite=True,
+        )
+        self.assertModule(module)
+
+        self.assertRasterExists(self.output)
+
+        expected_stats = {"n": 0}
+        self.assertRasterFitsUnivar(self.output, reference=expected_stats)
+
+    def test_ignore_zero_values(self):
+        """Test r.buffer with input raster of only zero values using -z flag."""
+        zero_map = "zero_map"
+        self.runModule("r.mapcalc", expression=f"{zero_map} = 0")
+
+        distances = [100]
+
+        module = SimpleModule(
+            "r.buffer",
+            input=zero_map,
+            output=self.output,
+            distances=distances,
+            flags="z",
+            overwrite=True,
+        )
+        self.assertModule(module)
+
+        self.assertRasterExists(self.output)
+
+        expected_stats = {"n": 0}
+        self.assertRasterFitsUnivar(self.output, reference=expected_stats)
+
+
+if __name__ == "__main__":
+    test()