Second checkpoint

internal/parser/parser_test.go

@@ -0,0 +1,48 @@
+package parser
+
+import "testing"
+
+func TestColumns_GeoJSON(t *testing.T) {
+	data := []byte(`{
+		"type": "FeatureCollection",
+		"features": [
+			{"type":"Feature","properties":{"ObjectID":1,"F_2023":100,"D_2025":200,"като":"751010000"},"geometry":null},
+			{"type":"Feature","properties":{"ObjectID":2,"F_2023":150,"D_2025":250,"като":"751020000"},"geometry":null}
+		]
+	}`)
+
+	cols, err := Columns("regions.geojson", data)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	// Order must follow the first feature's properties.
+	wantNames := []string{"ObjectID", "F_2023", "D_2025", "като"}
+	if len(cols) != len(wantNames) {
+		t.Fatalf("want %d columns, got %d (%+v)", len(wantNames), len(cols), cols)
+	}
+	for i, want := range wantNames {
+		if cols[i].Name != want {
+			t.Errorf("column %d = %q, want %q", i, cols[i].Name, want)
+		}
+	}
+
+	// KATO column should carry sample values from both features.
+	kato := cols[3]
+	if len(kato.Samples) != 2 || kato.Samples[0] != "751010000" {
+		t.Errorf("unexpected kato samples: %v", kato.Samples)
+	}
+}
+
+func TestColumns_UnsupportedFormat(t *testing.T) {
+	if _, err := Columns("data.txt", []byte("x")); err == nil {
+		t.Fatal("expected error for unsupported format")
+	}
+}
+
+func TestColumns_GeoJSONNoFeatures(t *testing.T) {
+	_, err := Columns("empty.geojson", []byte(`{"type":"FeatureCollection","features":[]}`))
+	if err == nil {
+		t.Fatal("expected error for empty feature collection")
+	}
+}