i.spectral: fix text output to write band values

scripts/i.spectral/i.spectral.py

@@ -89,11 +89,8 @@ def cleanup():
 
 
 def write2textf(what, output):
-    i = 0
-    with open(output, "w") as outf:
-        for row in enumerate(what):
-            i += 1
-            outf.write("%d, %s\n" % (i, row))
+    with open(output, "w", encoding="utf-8") as outf:
+        outf.writelines("%d, %s\n" % (i + 1, row[3:]) for i, row in enumerate(what))
 
 
 def draw_gnuplot(what, xlabels, output, img_format, coord_legend):

scripts/i.spectral/tests/i_spectral_test.py

@@ -0,0 +1,34 @@
+"""Tests of i.spectral"""
+
+import ast
+
+from grass.tools import Tools
+
+
+def test_text_output_writes_band_values_per_pick(
+    xy_raster_dataset_session_mapset, tmp_path
+):
+    """The -t text output lists each pick's band values, numbered per pick.
+
+    Regression test: write2textf iterated with `for row in enumerate(what)`, so
+    it wrote the `(index, row)` tuple verbatim instead of the band values. Two
+    coordinate pairs also check the per-pick numbering.
+    """
+    tools = Tools(session=xy_raster_dataset_session_mapset)
+    tools.g_region(n=10, s=0, w=0, e=10, res=1)
+    tools.r_mapcalc(expression="b1 = 10")
+    tools.r_mapcalc(expression="b2 = 20")
+    tools.r_mapcalc(expression="b3 = 30")
+    output = tmp_path / "spectrum.txt"
+    tools.i_spectral(
+        raster="b1,b2,b3",
+        coordinates=(5, 5, 2, 2),
+        output=str(output),
+        flags="t",
+    )
+    lines = output.read_text(encoding="utf-8").splitlines()
+    assert len(lines) == 2
+    for expected_index, line in enumerate(lines, start=1):
+        index_str, _, values_str = line.partition(", ")
+        assert int(index_str) == expected_index
+        assert ast.literal_eval(values_str) == [10.0, 20.0, 30.0]