`collapse = TRUE` will collapse messages into source blocks, too.

```{r, test-a, collapse = TRUE, error = TRUE, strip.white = FALSE}
message("this is a message")

warning("this is a warning")

stop("this is an error")
```

Not collapsing or striping blank lines:

```{r, test-a, error = TRUE}
```

Collapsing without striping blank lines:

```{r, test-a, collapse = TRUE, error = TRUE}
```