problem: sporadic unit-test failure

src/test/groovy/io/emeraldpay/dshackle/rpc/TrackEthereumAddressSpec.groovy

@@ -113,6 +113,6 @@ class TrackEthereumAddressSpec extends Specification {
                 }
                 .expectNext(exp2).as("Second block")
                 .thenCancel()
-                .verify(Duration.ofSeconds(1))
+                .verify(Duration.ofSeconds(2))
     }
 }

src/test/groovy/io/emeraldpay/dshackle/test/EthereumHeadMock.groovy

@@ -31,6 +31,7 @@ class EthereumHeadMock implements Head {
 
     void nextBlock(BlockContainer block) {
         assert block != null
+        println("New block: ${block.height} / ${block.hash}")
         latest = block
         bus.onNext(block)
     }

src/test/groovy/io/emeraldpay/dshackle/test/EthereumUpstreamMock.groovy

@@ -65,6 +65,7 @@ class EthereumUpstreamMock extends EthereumUpstream {
                 methods, TestingCommons.objectMapper())
         setLag(0)
         setStatus(UpstreamAvailability.OK)
+        start()
     }
 
     void nextBlock(BlockContainer block) {

src/test/groovy/io/emeraldpay/dshackle/test/TestingCommons.groovy

@@ -76,7 +76,9 @@ class TestingCommons {
     }
 
     static Multistream aggregatedUpstream(EthereumUpstream up) {
-        return new EthereumMultistream(Chain.ETHEREUM, [up], Caches.default(objectMapper()), objectMapper())
+        return new EthereumMultistream(Chain.ETHEREUM, [up], Caches.default(objectMapper()), objectMapper()).tap {
+            start()
+        }
     }
 
     static CachesFactory emptyCaches() {