add a few more tests to split function

template/interpolate/funcs_test.go

@@ -204,10 +204,22 @@ func TestFuncSplit(t *testing.T) {
 	cases := []struct {
 		Input         string
 		Output        string
+		ErrorExpected bool
 	}{
 		{
 			`{{split build_name "-" 0}}`,
 			"foo",
+			false,
+		},
+		{
+			`{{split build_name "-" 1}}`,
+			"bar",
+			false,
+		},
+		{
+			`{{split build_name "-" 2}}`,
+			"",
+			true,
 		},
 	}
 
@@ -215,7 +227,7 @@ func TestFuncSplit(t *testing.T) {
 	for _, tc := range cases {
 		i := &I{Value: tc.Input}
 		result, err := i.Render(ctx)
-		if err != nil {
+		if (err == nil) == tc.ErrorExpected {
 			t.Fatalf("Input: %s\n\nerr: %s", tc.Input, err)
 		}