public IsJson(Matcher<? super ReadContext> jsonMatcher) {
        this.jsonMatcher = jsonMatcher;
    }
@Test
    public void shouldNotMatchInvalidJson() {
        assertThat(INVALID_JSON, not(isJson()));
        assertThat(new Object(), not(isJson()));
        assertThat(new Object[]{}, not(isJson()));
        assertThat("hi there", not(isJson()));
        assertThat(new Integer(42), not(isJson()));
        assertThat(Boolean.TRUE, not(isJson()));
        assertThat(false, not(isJson()));
        assertThat(null, not(isJson()));
    }