add basic systemd service monitoring (#1153)

Co-authored-by: Shelby Tucker <shelby.tucker@gmail.com>

internal/hub/ws/handlers_test.go

@@ -0,0 +1,75 @@
+//go:build testing
+
+package ws
+
+import (
+	"testing"
+
+	"github.com/henrygd/beszel/internal/common"
+	"github.com/henrygd/beszel/internal/entities/systemd"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSystemdInfoHandlerSuccess(t *testing.T) {
+	handler := &systemdInfoHandler{
+		result: &systemd.ServiceDetails{},
+	}
+
+	// Test successful handling with valid ServiceInfo
+	testDetails := systemd.ServiceDetails{
+		"Id":             "nginx.service",
+		"ActiveState":    "active",
+		"SubState":       "running",
+		"Description":    "A high performance web server",
+		"ExecMainPID":    1234,
+		"MemoryCurrent":  1024000,
+	}
+
+	response := common.AgentResponse{
+		ServiceInfo: testDetails,
+	}
+
+	err := handler.Handle(response)
+	assert.NoError(t, err)
+	assert.Equal(t, testDetails, *handler.result)
+}
+
+func TestSystemdInfoHandlerError(t *testing.T) {
+	handler := &systemdInfoHandler{
+		result: &systemd.ServiceDetails{},
+	}
+
+	// Test error handling when ServiceInfo is nil
+	response := common.AgentResponse{
+		ServiceInfo: nil,
+		Error:       "service not found",
+	}
+
+	err := handler.Handle(response)
+	assert.Error(t, err)
+	assert.Equal(t, "no systemd info in response", err.Error())
+}
+
+func TestSystemdInfoHandlerEmptyResponse(t *testing.T) {
+	handler := &systemdInfoHandler{
+		result: &systemd.ServiceDetails{},
+	}
+
+	// Test with completely empty response
+	response := common.AgentResponse{}
+
+	err := handler.Handle(response)
+	assert.Error(t, err)
+	assert.Equal(t, "no systemd info in response", err.Error())
+}
+
+func TestSystemdInfoHandlerLegacyNotSupported(t *testing.T) {
+	handler := &systemdInfoHandler{
+		result: &systemd.ServiceDetails{},
+	}
+
+	// Test that legacy format is not supported
+	err := handler.HandleLegacy([]byte("some data"))
+	assert.Error(t, err)
+	assert.Equal(t, "legacy format not supported", err.Error())
+}