On metrics

Some examples of wrong metrics

Code coverage

@Test
public void dummy_test_to_improve_coverage() {
Math.add(1, 1); // 1
// Oops, no assertion... // 2
}
  1. Math.add() will be executed
  2. But there’s no assertion on the result

Docker image size

Application startup time

Measuring influences the measured metric

Measuring is challenging

Measuring narrows down your perspective

Conclusion

  • Good metrics require an understanding of the context
  • The act of measuring itself will change the context, whether you like or not
  • The more relevant the metric, the harder it will be to measure correctly
  • Whatever the metric, it doesn’t reflect reality

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