Any samples to unit test fallback using Hystrix Spring Cloud - spring

Question

I wish to test the following scenarios:
Set the hystrix.command.default.execution.isolation.thread.timeoutInMillisecond value to a low value, and see how my application behaves.
Check my fallback method is called using Unit test.
Please can someone provide me with link to samples.

Answer 1

A real usage can be found bellow. The key to enable Hystrix in the test class are these two annotations:
#EnableCircuitBreaker
#EnableAspectJAutoProxy
class ClipboardService {
#HystrixCommand(fallbackMethod = "getNextClipboardFallback")
public Task getNextClipboard(int numberOfTasks) {
doYourExternalSystemCallHere....
}
public Task getNextClipboardFallback(int numberOfTasks) {
return null;
}
}
#RunWith(SpringRunner.class)
#EnableCircuitBreaker
#EnableAspectJAutoProxy
#TestPropertySource("classpath:test.properties")
#ContextConfiguration(classes = {ClipboardService.class})
public class ClipboardServiceIT {
private MockRestServiceServer mockServer;
#Autowired
private ClipboardService clipboardService;
#Before
public void setUp() {
this.mockServer = MockRestServiceServer.createServer(restTemplate);
}
#Test
public void testGetNextClipboardWithBadRequest() {
mockServer.expect(ExpectedCount.once(), requestTo("https://getDocument.com?task=1")).andExpect(method(HttpMethod.GET))
.andRespond(MockRestResponseCreators.withStatus(HttpStatus.BAD_REQUEST));
Task nextClipboard = clipboardService.getNextClipboard(1);
assertNull(nextClipboard); // this should be answered by your fallBack method
}
}

Answer 2

Fore open the circuit in your unit test case just before you call the client. Make sure fall back is called. You can have a constant returned from fallback or add some log statements.
Reset the circuit.
#Test
public void testSendOrder_openCircuit() {
String order = null;
ServiceResponse response = null;
order = loadFile("/order.json");
// use this in case of feign hystrix
ConfigurationManager.getConfigInstance()
.setProperty("hystrix.command.default.circuitBreaker.forceOpen", "true");
// use this in case of just hystrix
System.setProperty("hystrix.command.default.circuitBreaker.forceOpen", "true");
response = client.sendOrder(order);
assertThat(response.getResultStatus()).isEqualTo("Fallback");
// DONT forget to reset
ConfigurationManager.getConfigInstance()
.setProperty("hystrix.command.default.circuitBreaker.forceOpen", "false");
// use this in case of just hystrix
System.setProperty("hystrix.command.default.circuitBreaker.forceOpen", "false");
}