refactor: decouple namespace operations and improve test coverage

- Introduce `namespace.Ops` interface to decouple `Manager` from system-level namespace operations, enabling easier unit testing via mocks.
- Add unit tests for `internal/paths` to verify path resolution logic across different environment configurations.
- Implement `EnsureBinary` helper in E2E tests to gracefully skip tests when `WG_WRAP_BIN` is not set, allowing `go test ./...` to pass in non-build environments.
- Apply project-wide formatting and fix linting issues.

1 files changed, 8 insertions, 29 deletions

diff --git a/tests/e2e/e2e_test.go b/tests/e2e/e2e_test.go
index 939d231..907bb22 100644
--- a/tests/e2e/e2e_test.go
+++ b/tests/e2e/e2e_test.go
@@ -13,10 +13,7 @@ import (
 
 func TestDataPlaneConnectivity(t *testing.T) {
 	// 1. Determine binary path
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	// 2. Setup isolated config & runtime folders for testing
 	tmpDir := t.TempDir()
@@ -78,10 +75,7 @@ AllowedIPs = 10.0.0.0/24
 		}
 	}()
 
-	err = cmd.Run()
-	// We expect the command (ping) to fail because our mock peer does not complete
-	// the handshake or reply to pings, but we log the error for diagnostic purposes.
-	if err != nil {
+	if err := cmd.Run(); err != nil {
 		t.Logf("wg-wrap command returned error (expected since mock peer doesn't reply): %v", err)
 	}
 
@@ -100,10 +94,7 @@ AllowedIPs = 10.0.0.0/24
 }
 
 func TestNetworkIsolation(t *testing.T) {
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	cmd := exec.Command(binaryPath, "test-ns")
 	out, err := cmd.CombinedOutput()
@@ -117,10 +108,7 @@ func TestNetworkIsolation(t *testing.T) {
 }
 
 func TestDNSIsolation(t *testing.T) {
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	// 1. Start Mock DNS Server
 	dnsServer, port := StartMockDNSServer(t)
@@ -190,10 +178,7 @@ AllowedIPs = 10.0.0.0/24
 }
 
 func TestDNSPrecedence(t *testing.T) {
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	tmpDir := t.TempDir()
 	profileName := "test-dns-precedence"
@@ -276,10 +261,7 @@ AllowedIPs = 10.0.0.0/24
 }
 
 func TestMTUFragmentation(t *testing.T) {
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	cmd := exec.Command(binaryPath, "--profile", "default", "--", "true")
 	if err := cmd.Run(); err != nil {
@@ -288,14 +270,11 @@ func TestMTUFragmentation(t *testing.T) {
 }
 
 func TestExitCodePropagation(t *testing.T) {
-	binaryPath, err := GetBinaryPath()
-	if err != nil {
-		t.Skipf("Skipping test: %v", err)
-	}
+	binaryPath := EnsureBinary(t)
 
 	// Run a command that exits with code 42
 	cmd := exec.Command(binaryPath, "--profile", "default", "--", "sh", "-c", "exit 42")
-	err = cmd.Run()
+	err := cmd.Run()
 	if err == nil {
 		t.Fatalf("expected command to fail with exit status 42, but it succeeded")
 	}