[tmpnet] Enable network restart to simplify iteration (#3272)

tests/e2e/README.md

@@ -77,6 +77,17 @@ If a network is not already running the first time the suite runs with
 `--reuse-network`, one will be started automatically and configured
 for reuse by subsequent test runs also supplying `--reuse-network`.
 
+### Restarting temporary networks
+
+When iterating on a change to avalanchego and/or a VM, it may be
+useful to restart a running network to ensure the network is using the
+latest binary state. Supplying `--restart-network` in addition to
+`--reuse-network` will ensure that all nodes are restarted before
+tests are run. `--restart-network` is ignored if a network is not
+running or if `--stop-network` is supplied.
+
+### Stopping temporary networks
+
 To stop a network configured for reuse, invoke the test suite with the
 `--stop-network` argument. This will stop the network and exit
 immediately without executing any tests:

tests/fixture/e2e/env.go

@@ -110,6 +110,9 @@ func NewTestEnvironment(tc tests.TestContext, flagVars *FlagVars, desiredNetwork
 				tc.Outf("No network to stop\n")
 			}
 			os.Exit(0)
+		} else if network != nil && flagVars.RestartNetwork() {
+			// A network is only restarted if it is already running and stop was not requested
+			require.NoError(network.Restart(tc.DefaultContext(), tc.GetWriter()))
 		}
 	}
 

tests/fixture/e2e/flags.go

@@ -19,6 +19,7 @@ type FlagVars struct {
 	reuseNetwork         bool
 	delayNetworkShutdown bool
 	stopNetwork          bool
+	restartNetwork       bool
 	nodeCount            int
 	activateEtna         bool
 }
@@ -45,6 +46,10 @@ func (v *FlagVars) ReuseNetwork() bool {
 	return v.reuseNetwork
 }
 
+func (v *FlagVars) RestartNetwork() bool {
+	return v.restartNetwork
+}
+
 func (v *FlagVars) NetworkShutdownDelay() time.Duration {
 	if v.delayNetworkShutdown {
 		// Only return a non-zero value if the delay is enabled.  Make sure this value takes
@@ -92,6 +97,12 @@ func RegisterFlags() *FlagVars {
 		false,
 		"[optional] reuse an existing network. If an existing network is not already running, create a new one and leave it running for subsequent usage.",
 	)
+	flag.BoolVar(
+		&vars.restartNetwork,
+		"restart-network",
+		false,
+		"[optional] restarts an existing network. Useful for ensuring a network is running with the current state of binaries on disk. Ignored if a network is not already running or --stop-network is provided.",
+	)
 	flag.BoolVar(
 		&vars.delayNetworkShutdown,
 		"delay-network-shutdown",