I have implemented Micrometer Prometheus counter in my service by injecting `MeterRegistry` and incrementing the count as shown below, and I have written a test case as well, but when I am running the test case, I am getting:

> 
> "java.lang.NullPointerException: Cannot invoke
> "io.micrometer.core.instrument.MeterRegistry.counter(String,
> String[])" because "this.meterRegistry" is null".
> 
> 
> 

Service file:

```java
@Autowired
private MeterRegistry meterRegistry;

public void counterIncrement() { 
    meterRegistry.counter("test_count").increment();
}

```

Test case file:

```java
@MockBean
private MeterRegistry registry;

@Test
void testCounter() {
    //  invoking counterIncrement();
}

```