@Test
public void variableWrapper() throws Exception {

    VariableWrapper wrapper = (params, prePunct, str, postPunct) -> {
        if (params.getContext() == Context.CITATION &&
                Arrays.asList(params.getVariableNames()).contains("author")) {
            return prePunct + "<strong>" + str + "</strong>" + postPunct;
        }
        return prePunct + str + postPunct;
    };
    try (CSL citeproc = new CSLBuilder()
            .itemDataProvider(new ListItemDataProvider(items))
            .variableWrapper(wrapper)
            .style("chicago-note-bibliography")
            .build()) {
        List<Citation> a = citeproc.makeCitation(items[0].getId());
        assertEquals(0, a.get(0).getIndex());
        assertEquals("<strong>Johnson and Kernighan</strong>, "
                        + "\u201cThe Programming Language B.\u201d",
                a.get(0).getText());
    }
}