@Test
    public void testMetricKeyWithNullMetricName() {
        Exception e = assertThrows(NullPointerException.class, () -> metricNamingStrategy.metricKey(null));
        assertEquals("metric name cannot be null", e.getMessage());
    }
Test metric key with mixed name and mixed tags where mixed represents combination of upper case,
lower case, numbers, hyphen, dot, underscore and special characters.
clients/src/test/java/org/apache/kafka/common/telemetry/internals/TelemetryMetricNamingConventionTest.java