@BeforeEach void init() {
    // We use DirtiesContext, not registry.clear(), as the latter would cause an empty scrape
    storage.clear();
  }
Tests here look at values based on counter values, so need to run independently. It would seem
correct to {@link PrometheusMeterRegistry#clear() clear the registry} to isolate counters
incremented in one test from interfering with another. However, this clears the metrics
themselves, resulting in an empty {@link PrometheusMeterRegistry#scrape()}.

<p>Currently, the only way we know how to reset the whole registry is to recreate the Spring
context, via {@link DirtiesContext} on each test. This is extremely slow, so please only add
tests that require isolation here!
zipkin-server/src/test/java/zipkin2/server/internal/prometheus/ITZipkinMetricsDirty.java