fix(agent/usershell): check shell on darwin via dscl (#8366)

agent/usershell/usershell_test.go

@@ -0,0 +1,46 @@
+package usershell_test
+
+import (
+	"os/user"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/agent/usershell"
+)
+
+//nolint:paralleltest,tparallel // This test sets an environment variable.
+func TestGet(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.SkipNow()
+	}
+
+	t.Run("Fallback", func(t *testing.T) {
+		t.Setenv("SHELL", "/bin/sh")
+
+		t.Run("NonExistentUser", func(t *testing.T) {
+			shell, err := usershell.Get("notauser")
+			require.NoError(t, err)
+			require.Equal(t, "/bin/sh", shell)
+		})
+	})
+
+	t.Run("NoFallback", func(t *testing.T) {
+		// Disable env fallback for these tests.
+		t.Setenv("SHELL", "")
+
+		t.Run("NotFound", func(t *testing.T) {
+			_, err := usershell.Get("notauser")
+			require.Error(t, err)
+		})
+
+		t.Run("User", func(t *testing.T) {
+			u, err := user.Current()
+			require.NoError(t, err)
+			shell, err := usershell.Get(u.Username)
+			require.NoError(t, err)
+			require.NotEmpty(t, shell)
+		})
+	})
+}