fix: NPE in BrokersServiceImplTest (#518)

Signed-off-by: tison <wander4096@gmail.com>

Author: tisonkun

src/test/java/org/apache/pulsar/manager/service/BrokersServiceImplTest.java

@@ -48,6 +48,9 @@ public class BrokersServiceImplTest {
     @MockBean
     private PulsarAdminService pulsarAdminService;
 
+    @MockBean
+    private EnvironmentCacheService environmentCacheService;
+
     @Autowired
     private BrokersService brokersService;
 
@@ -71,6 +74,9 @@ public void brokersServiceTest() throws Exception{
         Mockito.when(brokers.getActiveBrokers("standalone"))
                 .thenReturn(Arrays.asList("broker-1:8080"));
 
+        Mockito.when(environmentCacheService.getEnvironment("http://localhost:8080"))
+                .thenReturn("env");
+
         Map<String, Object> result = brokersService.getBrokersList(
                 1, 1, "standalone", "http://localhost:8080");
         Assert.assertEquals(1, result.get("total"));