@Override
    public void write(int c) {
        mBuffer.append((char) c);
    }
@Test
    void testWrite() {
        UnsafeStringWriter writer = new UnsafeStringWriter();
        writer.write("a");
        writer.write("abc", 1, 1);
        writer.write(99);
        writer.flush();
        writer.close();

        assertThat(writer.toString(), is("abc"));
    }