public IsJson(Matcher<? super ReadContext> jsonMatcher) {
        this.jsonMatcher = jsonMatcher;
    }
@Test
    public void shouldDescribeMismatchOfInvalidJson() {
        Matcher<Object> matcher = isJson(withPathEvaluatedTo(true));
        Description description = new StringDescription();
        matcher.describeMismatch("invalid-json", description);
        assertThat(description.toString(), containsString("\"invalid-json\""));
    }