Dashboard Migrations: V28 singlestat panel and deprecated variable properties (#108416)

Co-authored-by: Ivan Ortega <ivanortegaalba@gmail.com>

apps/dashboard/pkg/migration/testutil/mocks.go

@@ -1,9 +1,15 @@
 package testutil
 
-import "github.com/grafana/grafana/apps/dashboard/pkg/migration/schemaversion"
+import (
+	"github.com/grafana/grafana/apps/dashboard/pkg/migration/schemaversion"
+)
 
 type TestDataSourceProvider struct{}
 
+type TestPanelProvider struct {
+	customPanels []schemaversion.PanelPluginInfo
+}
+
 func (m *TestDataSourceProvider) GetDataSourceInfo() []schemaversion.DataSourceInfo {
 	return []schemaversion.DataSourceInfo{
 		{
@@ -57,7 +63,50 @@ func (m *TestDataSourceProvider) GetDataSourceInfo() []schemaversion.DataSourceI
 	}
 }
 
-// GetTestProvider returns a singleton instance of the test provider
-func GetTestProvider() *TestDataSourceProvider {
+func (m *TestPanelProvider) GetPanels() []schemaversion.PanelPluginInfo {
+	if len(m.customPanels) > 0 {
+		return m.customPanels
+	}
+
+	// Default panels
+	return []schemaversion.PanelPluginInfo{
+		{
+			ID:      "gauge",
+			Version: "1.0.0",
+		},
+		{
+			ID:      "stat",
+			Version: "1.0.0",
+		},
+		// Note: grafana-singlestat-panel is not included to match frontend test environment
+		// This ensures both frontend and backend migrations produce the same result
+	}
+}
+
+func (m *TestPanelProvider) GetPanelPlugin(id string) schemaversion.PanelPluginInfo {
+	// check if it exists in the list of mocked panels
+	for _, panel := range m.GetPanels() {
+		if panel.ID == id {
+			return panel
+		}
+	}
+
+	return schemaversion.PanelPluginInfo{}
+}
+
+// GetTestDataSourceProvider returns a singleton instance of the test provider
+func GetTestDataSourceProvider() *TestDataSourceProvider {
 	return &TestDataSourceProvider{}
 }
+
+// GetTestPanelProvider returns a singleton instance of the test panel provider
+func GetTestPanelProvider() *TestPanelProvider {
+	return &TestPanelProvider{}
+}
+
+// GetTestPanelProviderWithCustomPanels returns a test panel provider with custom panels
+func GetTestPanelProviderWithCustomPanels(customPanels []schemaversion.PanelPluginInfo) *TestPanelProvider {
+	return &TestPanelProvider{
+		customPanels: customPanels,
+	}
+}