diff --git a/doctor/ethtool/ethtool_test.go b/doctor/ethtool/ethtool_test.go
new file mode 100644
index 000000000..32918079e
--- /dev/null
+++ b/doctor/ethtool/ethtool_test.go
@@ -0,0 +1,21 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package ethtool
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestGetUDPGROTable(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("ethtool only on Linux")
+	}
+	
+	table, err := GetUDPGROTable()
+	if err != nil {
+		t.Logf("GetUDPGROTable returned error (expected on non-Linux or without permissions): %v", err)
+	}
+	_ = table
+}
diff --git a/doctor/routetable/routetable_test.go b/doctor/routetable/routetable_test.go
new file mode 100644
index 000000000..6e822b96e
--- /dev/null
+++ b/doctor/routetable/routetable_test.go
@@ -0,0 +1,19 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package routetable
+
+import "testing"
+
+func TestGet(t *testing.T) {
+	routes, err := Get(10000)
+	if err != nil {
+		t.Logf("Get returned error: %v", err)
+	}
+	_ = routes
+}
+
+func TestRouteTable(t *testing.T) {
+	rt := RouteTable{}
+	_ = rt.String()
+}
diff --git a/gokrazy/gokrazy_test.go b/gokrazy/gokrazy_test.go
new file mode 100644
index 000000000..18421b448
--- /dev/null
+++ b/gokrazy/gokrazy_test.go
@@ -0,0 +1,11 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package gokrazy
+
+import "testing"
+
+func TestIsGokrazy(t *testing.T) {
+	_ = IsGokrazy()
+	// Just verify it doesn't panic
+}
diff --git a/kube/kubeclient/kubeclient_test.go b/kube/kubeclient/kubeclient_test.go
new file mode 100644
index 000000000..2b6587ec8
--- /dev/null
+++ b/kube/kubeclient/kubeclient_test.go
@@ -0,0 +1,17 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package kubeclient
+
+import "testing"
+
+func TestIsNotFoundErr(t *testing.T) {
+	if IsNotFoundErr(nil) {
+		t.Error("IsNotFoundErr(nil) = true, want false")
+	}
+}
+
+func TestNamespaceFile(t *testing.T) {
+	_ = namespaceFile
+	// Constant should be defined
+}
diff --git a/wgengine/capture/capture_test.go b/wgengine/capture/capture_test.go
new file mode 100644
index 000000000..c2ee5c6fe
--- /dev/null
+++ b/wgengine/capture/capture_test.go
@@ -0,0 +1,24 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package capture
+
+import "testing"
+
+func TestNew(t *testing.T) {
+	c := New()
+	if c == nil {
+		t.Fatal("New() returned nil")
+	}
+}
+
+func TestCapture_Start(t *testing.T) {
+	c := New()
+	defer c.Close()
+	
+	// Basic test - should not panic
+	err := c.Start("test.pcap")
+	if err != nil {
+		t.Logf("Start returned error (expected on some platforms): %v", err)
+	}
+}
diff --git a/wgengine/netlog/logger_test.go b/wgengine/netlog/logger_test.go
new file mode 100644
index 000000000..eb3318322
--- /dev/null
+++ b/wgengine/netlog/logger_test.go
@@ -0,0 +1,25 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package netlog
+
+import (
+	"testing"
+	"time"
+)
+
+func TestLogger(t *testing.T) {
+	logger := NewLogger(nil, nil)
+	if logger == nil {
+		t.Fatal("NewLogger returned nil")
+	}
+}
+
+func TestMessage(t *testing.T) {
+	m := Message{
+		Start: time.Now(),
+	}
+	if m.Start.IsZero() {
+		t.Error("Message.Start is zero")
+	}
+}