Fix Math Logic in Confirming Assertion By Challenge Win (#602)

challenge-manager/chain-watcher/BUILD.bazel

@@ -30,4 +30,14 @@ go_test(
     name = "chain-watcher_test",
     srcs = ["watcher_test.go"],
     embed = [":chain-watcher"],
+    deps = [
+        "//chain-abstraction:protocol",
+        "//containers/option",
+        "//containers/threadsafe",
+        "//layer2-state-provider",
+        "//solgen/go/challengeV2gen",
+        "//testing/mocks",
+        "@com_github_ethereum_go_ethereum//common",
+        "@com_github_stretchr_testify//require",
+    ],
 )

challenge-manager/chain-watcher/watcher.go

@@ -807,11 +807,12 @@ func (w *Watcher) confirmAssertionByChallengeWinner(ctx context.Context, edge pr
 		log.Error("Could not get parent assertion creation info", log.Ctx{"error": err})
 		return
 	}
-	confirmableAtBlock := assertionCreationInfo.CreationBlock + parentCreationInfo.ConfirmPeriodBlocks
-	if edgeConfirmedAtBlock > confirmableAtBlock {
-		confirmableAtBlock = edgeConfirmedAtBlock
-	}
-	confirmableAtBlock += challengeGracePeriodBlocks
+	confirmableAtBlock := challengedAssertionConfirmableBlock(
+		parentCreationInfo,
+		edgeConfirmedAtBlock,
+		assertionCreationInfo,
+		challengeGracePeriodBlocks,
+	)
 
 	// Compute the number of blocks until we reach the assertion's
 	// deadline for confirmation.
@@ -845,6 +846,19 @@ func (w *Watcher) confirmAssertionByChallengeWinner(ctx context.Context, edge pr
 	}
 }
 
+func challengedAssertionConfirmableBlock(
+	parentInfo *protocol.AssertionCreatedInfo,
+	winningEdgeConfirmationBlock uint64,
+	info *protocol.AssertionCreatedInfo,
+	challengeGracePeriodBlocks uint64,
+) uint64 {
+	confirmableAtBlock := info.CreationBlock + parentInfo.ConfirmPeriodBlocks
+	if winningEdgeConfirmationBlock+challengeGracePeriodBlocks > confirmableAtBlock {
+		confirmableAtBlock = winningEdgeConfirmationBlock + challengeGracePeriodBlocks
+	}
+	return confirmableAtBlock
+}
+
 type filterRange struct {
 	startBlockNum uint64
 	endBlockNum   uint64