Refactor shell package and use getent for user/group lookup

client/internal/shell/shell_test.go

@@ -0,0 +1,26 @@
+package shell
+
+import (
+	"os/user"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestIntegration_ShellLookupChain tests the full shell resolution chain
+// (getShellFromPasswd -> getShellFromGetent -> $SHELL -> default) on Unix.
+func TestIntegration_ShellLookupChain(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Unix shell lookup not applicable on Windows")
+	}
+
+	current, err := user.Current()
+	require.NoError(t, err)
+
+	// getUserShell is the top-level function used by the SSH server.
+	shell := GetUserShell(current.Uid)
+	require.NotEmpty(t, shell, "getUserShell must always return a shell")
+	assert.True(t, shell[0] == '/', "shell should be an absolute path, got %q", shell)
+}