### Question:
NetworkUsageMetricsCollector { void addTxBytes(long bytes) { metrics.addTxBytesForType(getActiveNetworkType(), bytes); } NetworkUsageMetricsCollector(Context context, TelemetryMetrics metrics);   }### Answer:
@Test public void addTxBytes() { networkUsageMetricsCollector.addTxBytes(30); verify(metrics).addTxBytesForType(anyInt(), anyLong()); }