[tmpnet] Ensure tmpnet compatibility with windows

This avoids breaking unit test discovery for any package that imports
tmpnet.

scripts/build_test.sh

@@ -9,12 +9,6 @@ source "$AVALANCHE_PATH"/scripts/constants.sh
 
 EXCLUDED_TARGETS="| grep -v /mocks | grep -v proto | grep -v tests/e2e | grep -v tests/upgrade"
 
-GOOS=$(go env GOOS)
-if [[ "$GOOS" == "windows" ]]; then
-  # tmpnet and antithesis tests (which depend on tmpnet) are not compatible with windows
-  EXCLUDED_TARGETS="${EXCLUDED_TARGETS} | grep -v tests/fixture | grep -v tests/antithesis"
-fi
-
 TEST_TARGETS="$(eval "go list ./... ${EXCLUDED_TARGETS}")"
 
 # shellcheck disable=SC2086

tests/fixture/tmpnet/detached_process_others.go

@@ -0,0 +1,17 @@
+// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+//go:build linux || darwin
+
+package tmpnet
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func configureDetachedProcess(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setsid: true,
+	}
+}

tests/fixture/tmpnet/detached_process_windows.go

@@ -0,0 +1,17 @@
+// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+//go:build windows
+
+package tmpnet
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func configureDetachedProcess(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		CreationFlags: syscall.CREATE_NEW_PROCESS_GROUP,
+	}
+}

tests/fixture/tmpnet/node_process.go

@@ -114,11 +114,8 @@ func (p *NodeProcess) Start(w io.Writer) error {
 
 	// All arguments are provided in the flags file
 	cmd := exec.Command(p.node.RuntimeConfig.AvalancheGoPath, "--config-file", p.node.getFlagsPath()) // #nosec G204
-
 	// Ensure process is detached from the parent process so that an error in the parent will not affect the child
-	cmd.SysProcAttr = &syscall.SysProcAttr{
-		Setsid: true,
-	}
+	configureDetachedProcess(cmd)
 
 	if err := cmd.Start(); err != nil {
 		return err