[market] Require a storage contract with a signer

dagger/contracts/market.nim

@@ -1,5 +1,6 @@
 import pkg/ethers
 import pkg/upraises
+import pkg/questionable
 import ../market
 import ./storage
 
@@ -15,7 +16,9 @@ type
 export market
 
 func new*(_: type OnChainMarket, contract: Storage): OnChainMarket =
-  OnChainMarket(contract: contract, signer: !contract.signer)
+  without signer =? contract.signer:
+    raiseAssert("Storage contract should have a signer")
+  OnChainMarket(contract: contract, signer: signer)
 
 method subscribeRequests(market: OnChainMarket,
                          callback: OnRequest):

tests/contracts/testMarket.nim

@@ -16,6 +16,11 @@ ethersuite "On-Chain Market":
     await token.mint(accounts[0], 1000.u256)
     market = OnChainMarket.new(storage)
 
+  test "fails to instantiate when contract does not have a signer":
+    let storageWithoutSigner = storage.connect(provider)
+    expect AssertionError:
+      discard OnChainMarket.new(storageWithoutSigner)
+
   test "supports storage requests":
     var submitted: seq[StorageRequest]
     proc onRequest(request: StorageRequest) =