### Question:
SystemMetrics implements Serializable { public abstract T sum(@Nullable T b, @Nullable T output);  abstract T sum(@Nullable T b, @Nullable T output); abstract T diff(@Nullable T b, @Nullable T output); abstract T set(T b); T sum(@Nullable T b); T diff(@Nullable T b);  }### Answer:
@Test public void testSum() throws Exception { T a = createInitializedInstance(); int increment = 1; for (Field field : getClazz().getFields()) { if (MetricsUtil.isNumericField(field)) { field.set(a, 2 * increment); increment += 1; } } T b = createInitializedInstance(); T sum = createInstance(); a.sum(b, sum); increment = 1; for (Field field : getClazz().getFields()) { if (MetricsUtil.isNumericField(field)) { MetricsUtil.testValue(sum, field, 3 * increment); increment += 1; } } }