builder = new DefaultMessageBuilder();
        format.formatRate(builder, 5500.0); // 5.5 kB/s
        assertEquals("5.5 kB/s", builder.build());

        // Test exact unit thresholds
        builder = new DefaultMessageBuilder();
        format.formatRate(builder, 1000.0); // 1 kB/s
        assertEquals("1.0 kB/s", builder.build());

        builder = new DefaultMessageBuilder();