### Question:
K8sMetricsAutoConfiguration implements MeterRegistryCustomizer { @Override public void customize(MeterRegistry registry) { String commonTagNameValuePair = metricsProperties.getCommonTagNameValuePairs(); if (commonTagNameValuePair != null && !commonTagNameValuePair.isEmpty()) { String[] pairs = commonTagNameValuePair.split(","); for(String p : pairs) { String[] nameAndValue = p.split(":"); if (nameAndValue == null || nameAndValue.length != 2) { throw new IllegalStateException("Invalid common tag name value pair:" + p); } String valuePattern = nameAndValue[1]; int sepIndex = valuePattern.indexOf('|'); String[] patterns = null; if (sepIndex > 0) { patterns = valuePattern.split(Pattern.quote("|")); } else { patterns = new String[] { valuePattern }; } for(int i = 0; i < patterns.length; i ++) { String value = null; if (patterns[i].startsWith("ENV.")) { value = System.getenv(patterns[i].substring(4)); } else { value = System.getProperty(patterns[i]); if ((value == null || value.isEmpty()) && appContext != null) { value = appContext.getEnvironment().getProperty(patterns[i]); } } if (value != null && !value.isEmpty()) { registry.config().commonTags(nameAndValue[0], value); break; } } } } String statuses = metricsProperties.getInitializeForStatuses(); if (statuses != null || !statuses.isEmpty()) { String[] statusCodes = statuses.split(","); for(String code: statusCodes) { if (metricsProperties.hasCaller()) { registry.timer(HTTP_SERVER_REQUESTS, "exception", "None", "method", "GET", "status", code, "uri", "/**", "caller", "*", "outcome", "SERVER_ERROR"); } else { registry.timer(HTTP_SERVER_REQUESTS, "exception", "None", "method", "GET", "status", code, "uri", "/**", "outcome", "SERVER_ERROR"); } } } }  @Bean CommonMetricsFilter commonMetricsFilter(MetricsProperties properties); @Override void customize(MeterRegistry registry);  }### Answer:
@Test public void customize() { MeterRegistry registry = new CompositeMeterRegistry(); K8sMetricsAutoConfiguration k8sMetricsAutoConfiguration = new K8sMetricsAutoConfiguration(); k8sMetricsAutoConfiguration.metricsProperties = new K8sMetricsProperties(); k8sMetricsAutoConfiguration.customize(registry); }