fix: skip ADB-dependent tests when ADB server is unavailable

The interop/gadb tests require a running ADB server with a connected
device. In CI (GitHub Actions) there is no ADB server, causing
connection refused errors that fail the entire test suite.

Add requireADB() helpers that skip tests gracefully when the ADB
server is unreachable.

Author: xaionaro@dx.center

interop/gadb/proxy/proxy_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"testing"
 
+	"github.com/electricbubble/gadb"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -14,7 +15,17 @@ import (
 
 const testDeviceSerial = "41041JEKB08092"
 
+// requireADB skips the test if the ADB server is not reachable.
+func requireADB(t *testing.T) {
+	t.Helper()
+	if _, err := gadb.NewClient(); err != nil {
+		t.Skipf("ADB server not available: %v", err)
+	}
+}
+
 func TestSession(t *testing.T) {
+	requireADB(t)
+
 	ctx := context.Background()
 
 	session, err := proxy.NewSession(ctx, testDeviceSerial)

interop/gadb/runner/runner_test.go

@@ -9,14 +9,25 @@ import (
 	"testing"
 	"time"
 
-	"github.com/AndroidGoLab/binder/interop/gadb/runner"
+	"github.com/electricbubble/gadb"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/AndroidGoLab/binder/interop/gadb/runner"
 )
 
 const testDeviceSerial = "41041JEKB08092"
 
+// requireADB skips the test if the ADB server is not reachable.
+func requireADB(t *testing.T) {
+	t.Helper()
+	if _, err := gadb.NewClient(); err != nil {
+		t.Skipf("ADB server not available: %v", err)
+	}
+}
+
 func TestDiscoverDevices(t *testing.T) {
+	requireADB(t)
 	ctx := context.Background()
 
 	devices, err := runner.DiscoverDevices(ctx)
@@ -35,6 +46,8 @@ func TestDiscoverDevices(t *testing.T) {
 }
 
 func TestPushAndRun(t *testing.T) {
+	requireADB(t)
+
 	ctx := context.Background()
 
 	// Cross-compile examples/list_services for arm64.
@@ -68,6 +81,8 @@ func TestPushAndRun(t *testing.T) {
 }
 
 func TestRunWithTimeout(t *testing.T) {
+	requireADB(t)
+
 	ctx := context.Background()
 
 	dr, err := runner.NewDeviceRunner(testDeviceSerial)