diff --git a/.gitignore b/.gitignore
index 57dfc22..332b1f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ nimble.develop
 nimble.paths
 .idea
 .nimble
+.envrc
diff --git a/Readme.md b/Readme.md
index 2581e2b..df34b0c 100644
--- a/Readme.md
+++ b/Readme.md
@@ -202,6 +202,9 @@ $ npm ci
 $ npm start
 ```
 
+If you need to use different port for the RPC node, then you can start with `npm start -- --port 1111` and
+then run the tests with `ETHERS_TEST_PROVIDER=1111 nimble test`.
+
 Thanks
 ------
 
diff --git a/ethers/providers/jsonrpc/subscriptions.nim b/ethers/providers/jsonrpc/subscriptions.nim
index e2bc6cb..d9ea1dd 100644
--- a/ethers/providers/jsonrpc/subscriptions.nim
+++ b/ethers/providers/jsonrpc/subscriptions.nim
@@ -17,6 +17,7 @@ type
     methodHandlers: Table[string, MethodHandler]
   MethodHandler* = proc (j: JsonNode) {.gcsafe, raises: [].}
   SubscriptionCallback = proc(id, arguments: JsonNode) {.gcsafe, raises:[].}
+  SubscriptionError* = object of EthersError
 
 {.push raises:[].}
 
@@ -130,7 +131,7 @@ method unsubscribe*(subscriptions: WebSocketSubscriptions,
 # Polling
 
 type
-  PollingSubscriptions = ref object of JsonRpcSubscriptions
+  PollingSubscriptions* = ref object of JsonRpcSubscriptions
     polling: Future[void]
 
     # We need to keep around the filters that are used to create log filters on the RPC node
@@ -151,14 +152,24 @@ proc new*(_: type JsonRpcSubscriptions,
   proc getChanges(originalId: JsonNode): Future[JsonNode] {.async.} =
     try:
       let mappedId = subscriptions.subscriptionMapping[originalId]
-      return await subscriptions.client.eth_getFilterChanges(mappedId)
+      let changes = await subscriptions.client.eth_getFilterChanges(mappedId)
+      if changes.kind == JNull:
+        return newJArray()
+      elif changes.kind != JArray:
+        raise newException(SubscriptionError,
+          "HTTP polling: unexpected value returned from eth_getFilterChanges." &
+          " Expected: JArray, got: " & $changes.kind)
+      return changes
+    except CancelledError as e:
+      raise e
     except CatchableError as e:
       if "filter not found" in e.msg:
         let filter = subscriptions.filters[originalId]
         let newId = await subscriptions.client.eth_newFilter(filter)
         subscriptions.subscriptionMapping[originalId] = newId
-
-      return newJArray()
+        return await getChanges(originalId)
+      else:
+        raise e
 
   proc poll(id: JsonNode) {.async.} =
     for change in await getChanges(id):
@@ -218,7 +229,17 @@ method subscribeLogs(subscriptions: PollingSubscriptions,
 method unsubscribe*(subscriptions: PollingSubscriptions,
                    id: JsonNode)
                   {.async.} =
-  discard await subscriptions.client.eth_uninstallFilter(subscriptions.subscriptionMapping[id])
   subscriptions.filters.del(id)
   subscriptions.callbacks.del(id)
+  let sub = subscriptions.subscriptionMapping[id]
   subscriptions.subscriptionMapping.del(id)
+  try:
+    discard await subscriptions.client.eth_uninstallFilter(sub)
+  except CancelledError as e:
+    raise e
+  except CatchableError:
+    # Ignore if uninstallation of the filter fails. If it's the last step in our
+    # cleanup, then filter changes for this filter will no longer be polled so
+    # if the filter continues to live on in geth for whatever reason then it
+    # doesn't matter.
+    discard
diff --git a/testmodule/providers/jsonrpc/rpc_mock.nim b/testmodule/providers/jsonrpc/rpc_mock.nim
index d9cae74..5142a82 100644
--- a/testmodule/providers/jsonrpc/rpc_mock.nim
+++ b/testmodule/providers/jsonrpc/rpc_mock.nim
@@ -3,40 +3,39 @@ import ../../../ethers/provider
 import ../../../ethers/providers/jsonrpc/conversions
 
 import std/tables
+import std/sequtils
 import pkg/stew/byteutils
 import pkg/json_rpc/rpcserver except `%`, `%*`
 import pkg/json_rpc/errors
 
-
 type MockRpcHttpServer* = ref object
-  filters*: Table[string, bool]
-  newFilterCounter*: int
+  filters*: seq[string]
   srv: RpcHttpServer
 
 proc new*(_: type MockRpcHttpServer): MockRpcHttpServer =
-  MockRpcHttpServer(filters: initTable[string, bool](), newFilterCounter: 0, srv: newRpcHttpServer(["127.0.0.1:0"]))
+  let srv = newRpcHttpServer(["127.0.0.1:0"])
+  MockRpcHttpServer(filters: @[], srv: srv)
 
-proc invalidateFilter*(server: MockRpcHttpServer, id: string) =
-  server.filters[id] = false
+proc invalidateFilter*(server: MockRpcHttpServer, jsonId: JsonNode) =
+  server.filters.keepItIf it != jsonId.getStr
 
 proc start*(server: MockRpcHttpServer) =
   server.srv.router.rpc("eth_newFilter") do(filter: EventFilter) -> string:
     let filterId = "0x" & (array[16, byte].example).toHex
-    server.filters[filterId] = true
-    server.newFilterCounter += 1
+    server.filters.add filterId
     return filterId
 
   server.srv.router.rpc("eth_getFilterChanges") do(id: string) -> seq[string]:
-    if(not hasKey(server.filters, id) or not server.filters[id]):
+    if id notin server.filters:
       raise (ref ApplicationError)(code: -32000, msg: "filter not found")
 
     return @[]
 
   server.srv.router.rpc("eth_uninstallFilter") do(id: string) -> bool:
-    if(not hasKey(server.filters, id)):
+    if id notin server.filters:
       raise (ref ApplicationError)(code: -32000, msg: "filter not found")
 
-    server.filters.del(id)
+    server.invalidateFilter(%id)
     return true
 
   server.srv.start()
@@ -45,6 +44,5 @@ proc stop*(server: MockRpcHttpServer) {.async.} =
   await server.srv.stop()
   await server.srv.closeWait()
 
-
 proc localAddress*(server: MockRpcHttpServer): seq[TransportAddress] =
   return server.srv.localAddress()
diff --git a/testmodule/providers/jsonrpc/testJsonRpcProvider.nim b/testmodule/providers/jsonrpc/testJsonRpcProvider.nim
index 0a3620f..0f6e435 100644
--- a/testmodule/providers/jsonrpc/testJsonRpcProvider.nim
+++ b/testmodule/providers/jsonrpc/testJsonRpcProvider.nim
@@ -1,3 +1,4 @@
+import std/os
 import pkg/asynctest
 import pkg/chronos
 import pkg/ethers
@@ -6,7 +7,8 @@ import pkg/stew/byteutils
 import ../../examples
 import ../../miner
 
-for url in ["ws://localhost:8545", "http://localhost:8545"]:
+let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
+for url in ["ws://" & providerUrl, "http://"  & providerUrl]:
 
   suite "JsonRpcProvider (" & url & ")":
 
diff --git a/testmodule/providers/jsonrpc/testJsonRpcSigner.nim b/testmodule/providers/jsonrpc/testJsonRpcSigner.nim
index 34d78ea..e63a9a3 100644
--- a/testmodule/providers/jsonrpc/testJsonRpcSigner.nim
+++ b/testmodule/providers/jsonrpc/testJsonRpcSigner.nim
@@ -1,3 +1,4 @@
+import std/os
 import pkg/asynctest
 import pkg/ethers
 import pkg/stew/byteutils
@@ -7,9 +8,10 @@ suite "JsonRpcSigner":
 
   var provider: JsonRpcProvider
   var accounts: seq[Address]
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new()
+    provider = JsonRpcProvider.new("http://" & providerUrl)
     accounts = await provider.listAccounts()
 
   teardown:
diff --git a/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim b/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim
index d26f8d8..d0e2fff 100644
--- a/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim
+++ b/testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim
@@ -1,5 +1,7 @@
 import std/json
+import std/os
 import std/sequtils
+import std/importutils
 import pkg/asynctest
 import pkg/serde
 import pkg/json_rpc/rpcclient
@@ -68,7 +70,7 @@ suite "Web socket subscriptions":
 
   setup:
     client = newRpcWebSocketClient()
-    await client.connect("ws://localhost:8545")
+    await client.connect("ws://"  & getEnv("ETHERS_TEST_PROVIDER", "localhost:8545"))
     subscriptions = JsonRpcSubscriptions.new(client)
     subscriptions.start()
 
@@ -85,7 +87,7 @@ suite "HTTP polling subscriptions":
 
   setup:
     client = newRpcHttpClient()
-    await client.connect("http://localhost:8545")
+    await client.connect("http://" & getEnv("ETHERS_TEST_PROVIDER", "localhost:8545"))
     subscriptions = JsonRpcSubscriptions.new(client,
                                              pollingInterval = 100.millis)
     subscriptions.start()
@@ -98,10 +100,12 @@ suite "HTTP polling subscriptions":
 
 suite "HTTP polling subscriptions - filter not found":
 
-  var subscriptions: JsonRpcSubscriptions
+  var subscriptions: PollingSubscriptions
   var client: RpcHttpClient
   var mockServer: MockRpcHttpServer
 
+  privateAccess(PollingSubscriptions)
+
   setup:
     mockServer = MockRpcHttpServer.new()
     mockServer.start()
@@ -109,8 +113,10 @@ suite "HTTP polling subscriptions - filter not found":
     client = newRpcHttpClient()
     await client.connect("http://" & $mockServer.localAddress()[0])
 
-    subscriptions = JsonRpcSubscriptions.new(client,
-                                             pollingInterval = 15.millis)
+    subscriptions = PollingSubscriptions(
+                      JsonRpcSubscriptions.new(
+                        client,
+                        pollingInterval = 1.millis))
     subscriptions.start()
 
   teardown:
@@ -122,35 +128,28 @@ suite "HTTP polling subscriptions - filter not found":
     let filter = EventFilter(address: Address.example, topics: @[array[32, byte].example])
     let emptyHandler = proc(log: Log) = discard
 
-    check mockServer.newFilterCounter == 0
-    let jsonId = await subscriptions.subscribeLogs(filter, emptyHandler)
-    let id = string.fromJson(jsonId).tryGet
-    check mockServer.newFilterCounter == 1
+    check subscriptions.filters.len == 0
+    check subscriptions.subscriptionMapping.len == 0
+
+    let id = await subscriptions.subscribeLogs(filter, emptyHandler)
+
+    check subscriptions.filters[id] == filter
+    check subscriptions.subscriptionMapping[id] == id
+    check subscriptions.filters.len == 1
+    check subscriptions.subscriptionMapping.len == 1
 
-    await sleepAsync(50.millis)
     mockServer.invalidateFilter(id)
-    await sleepAsync(50.millis)
-    check mockServer.newFilterCounter == 2
+
+    check eventually subscriptions.subscriptionMapping[id] != id
 
   test "recreated filter can be still unsubscribed using the original id":
     let filter = EventFilter(address: Address.example, topics: @[array[32, byte].example])
     let emptyHandler = proc(log: Log) = discard
-
-    check mockServer.newFilterCounter == 0
-    let jsonId = await subscriptions.subscribeLogs(filter, emptyHandler)
-    let id = string.fromJson(jsonId).tryGet
-    check mockServer.newFilterCounter == 1
-
-    await sleepAsync(50.millis)
+    let id = await subscriptions.subscribeLogs(filter, emptyHandler)
     mockServer.invalidateFilter(id)
-    check eventually mockServer.newFilterCounter == 2
-    check mockServer.filters[id] == false
-    check mockServer.filters.len() == 2
-    await subscriptions.unsubscribe(jsonId)
-    check mockServer.filters.len() == 1
+    check eventually subscriptions.subscriptionMapping[id] != id
 
-    # invalidateFilter sets the filter's value to false which will return the "filter not found"
-    # unsubscribing will actually delete the key from filters table
-    # hence after unsubscribing the only key left in the table should be the original id
-    for key in mockServer.filters.keys():
-      check key == id
+    await subscriptions.unsubscribe(id)
+
+    check not subscriptions.filters.hasKey id
+    check not subscriptions.subscriptionMapping.hasKey id
diff --git a/testmodule/testContracts.nim b/testmodule/testContracts.nim
index 86079fa..ed2158a 100644
--- a/testmodule/testContracts.nim
+++ b/testmodule/testContracts.nim
@@ -1,4 +1,5 @@
 import std/json
+import std/os
 import std/options
 import pkg/asynctest
 import pkg/questionable
@@ -16,7 +17,8 @@ type
 method mint(token: TestToken, holder: Address, amount: UInt256): Confirmable {.base, contract.}
 method myBalance(token: TestToken): UInt256 {.base, contract, view.}
 
-for url in ["ws://localhost:8545", "http://localhost:8545"]:
+let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
+for url in ["ws://"  & providerUrl, "http://"  & providerUrl]:
 
   suite "Contracts (" & url & ")":
 
diff --git a/testmodule/testCustomErrors.nim b/testmodule/testCustomErrors.nim
index 2347d7d..e03ed95 100644
--- a/testmodule/testCustomErrors.nim
+++ b/testmodule/testCustomErrors.nim
@@ -1,3 +1,4 @@
+import std/os
 import std/json
 import pkg/asynctest
 import pkg/ethers
@@ -22,9 +23,10 @@ suite "Contract custom errors":
   var contract: TestCustomErrors
   var provider: JsonRpcProvider
   var snapshot: JsonNode
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new()
+    provider = JsonRpcProvider.new("http://" & providerUrl)
     snapshot = await provider.send("evm_snapshot")
     let deployment = readDeployment()
     let address = !deployment.address(TestCustomErrors)
diff --git a/testmodule/testEnums.nim b/testmodule/testEnums.nim
index 3686b93..50da630 100644
--- a/testmodule/testEnums.nim
+++ b/testmodule/testEnums.nim
@@ -1,3 +1,4 @@
+import std/os
 import pkg/asynctest
 import pkg/ethers
 import pkg/serde
@@ -14,9 +15,10 @@ suite "Contract enum parameters and return values":
   var contract: TestEnums
   var provider: JsonRpcProvider
   var snapshot: JsonNode
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new()
+    provider = JsonRpcProvider.new("http://" & providerUrl)
     snapshot = await provider.send("evm_snapshot")
     let deployment = readDeployment()
     contract = TestEnums.new(!deployment.address(TestEnums), provider)
diff --git a/testmodule/testErc20.nim b/testmodule/testErc20.nim
index 7f597f6..2eea2f7 100644
--- a/testmodule/testErc20.nim
+++ b/testmodule/testErc20.nim
@@ -1,3 +1,4 @@
+import std/os
 import std/json
 import pkg/asynctest
 import pkg/questionable
@@ -11,7 +12,8 @@ type
 
 method mint(token: TestToken, holder: Address, amount: UInt256): Confirmable {.base, contract.}
 
-for url in ["ws://localhost:8545", "http://localhost:8545"]:
+let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
+for url in ["ws://" & providerUrl, "http://"  & providerUrl]:
 
   suite "ERC20 (" & url & ")":
 
diff --git a/testmodule/testGasEstimation.nim b/testmodule/testGasEstimation.nim
index 5ee69c3..7c5001e 100644
--- a/testmodule/testGasEstimation.nim
+++ b/testmodule/testGasEstimation.nim
@@ -1,3 +1,4 @@
+import std/os
 import pkg/asynctest
 import pkg/ethers
 import pkg/serde
@@ -14,9 +15,10 @@ suite "gas estimation":
   var contract: TestGasEstimation
   var provider: JsonRpcProvider
   var snapshot: JsonNode
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new()
+    provider = JsonRpcProvider.new("http://" & providerUrl)
     snapshot = await provider.send("evm_snapshot")
     let deployment = readDeployment()
     let signer = provider.getSigner()
diff --git a/testmodule/testReturns.nim b/testmodule/testReturns.nim
index 2893f33..e4bab94 100644
--- a/testmodule/testReturns.nim
+++ b/testmodule/testReturns.nim
@@ -1,3 +1,4 @@
+import std/os
 import pkg/asynctest
 import pkg/ethers
 import pkg/serde
@@ -13,9 +14,10 @@ suite "Contract return values":
   var contract: TestReturns
   var provider: JsonRpcProvider
   var snapshot: JsonNode
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new()
+    provider = JsonRpcProvider.new("http://" & providerUrl)
     snapshot = await provider.send("evm_snapshot")
     let deployment = readDeployment()
     contract = TestReturns.new(!deployment.address(TestReturns), provider)
diff --git a/testmodule/testTesting.nim b/testmodule/testTesting.nim
index b5d80bd..30d95e9 100644
--- a/testmodule/testTesting.nim
+++ b/testmodule/testTesting.nim
@@ -1,3 +1,4 @@
+import std/os
 import std/strformat
 import pkg/asynctest
 import pkg/chronos
@@ -92,9 +93,10 @@ suite "Testing helpers - contracts":
   var snapshot: JsonNode
   var accounts: seq[Address]
   let revertReason = "revert reason"
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new("ws://127.0.0.1:8545")
+    provider = JsonRpcProvider.new("ws://" & providerUrl)
     snapshot = await provider.send("evm_snapshot")
     accounts = await provider.listAccounts()
     helpersContract = TestHelpers.new(provider.getSigner())
diff --git a/testmodule/testWallet.nim b/testmodule/testWallet.nim
index a3cdf2d..271cdd9 100644
--- a/testmodule/testWallet.nim
+++ b/testmodule/testWallet.nim
@@ -1,3 +1,4 @@
+import std/os
 import pkg/asynctest
 import pkg/serde
 import pkg/stew/byteutils
@@ -12,9 +13,10 @@ proc transfer*(erc20: Erc20, recipient: Address, amount: UInt256) {.contract.}
 suite "Wallet":
   var provider: JsonRpcProvider
   var snapshot: JsonNode
+  let providerUrl = getEnv("ETHERS_TEST_PROVIDER", "localhost:8545")
 
   setup:
-    provider = JsonRpcProvider.new()
+    provider = JsonRpcProvider.new("http://" & providerUrl)
     snapshot = await provider.send("evm_snapshot")
 
   teardown: