Bound generated text content and diagnostics

internal/generatedtext/today_test.go

@@ -62,7 +62,7 @@ func TestValidateTodayRejectsInvalidInput(t *testing.T) {
 		{
 			name: "unknown field",
 			in:   `{"summary":"Showers are likely today.","forecast_discussion":["A front will keep rain chances elevated."],"extra":"value"}`,
-			want: `unknown field "extra"`,
+			want: "unsupported field",
 		},
 		{
 			name: "missing summary",
@@ -87,7 +87,7 @@ func TestValidateTodayRejectsInvalidInput(t *testing.T) {
 		{
 			name: "forecast discussion wrong type",
 			in:   `{"summary":"Showers are likely today.","forecast_discussion":"A front will keep rain chances elevated."}`,
-			want: "cannot unmarshal string",
+			want: "forecast discussion must be an array",
 		},
 		{
 			name: "multiple values",