Test for knitr issue on include_graphics (https://github.com/yihui/knitr/pull/1776)

manual-test.Rmd

# one graphic

```{r, fig.cap = "This is a caption for unique figure"}
knitr::include_graphics("test-1.png")
```


# Three graphics in the same chunk

Using three times `include_graphics`

```{r, fig.cap = "This is a caption", out.width = "33%", fig.show = "hold"}
knitr::include_graphics("test-1.png")
knitr::include_graphics("test-2.png")
knitr::include_graphics("test-3.png")
```

```{r, fig.cap = "This is another caption", out.width = "33%", fig.show = "hold"}
knitr::include_graphics(c("test-1.png", "test-2.png", "test-3.png"))
```

# mixing with plot

```{r, fig.cap = "This is a caption", out.width = "33%", fig.show = "hold"}
knitr::include_graphics("test-1.png")
plot(iris)
knitr::include_graphics("test-2.png")
1+1
knitr::include_graphics("test-3.png")
```

```{r, fig.cap = c("This is a caption", "This is another", "this is a plot", "And a last"), out.width = "33%"}
knitr::include_graphics(c("test-1.png", "test-2.png"))
plot(iris)
1+1
knitr::include_graphics("test-3.png")
```

# Placing on top

```{r, fig.cap = "This is a caption", out.width = "33%", fig.show = "hold", fig.topcaption = TRUE}
knitr::include_graphics("test-1.png")
knitr::include_graphics("test-2.png")
knitr::include_graphics("test-3.png")
```

```{r, fig.cap = "This is another caption", out.width = "33%", fig.show = "hold", fig.topcaption = TRUE}
knitr::include_graphics(c("test-1.png", "test-2.png", "test-3.png"))
```