Fix dashboard migration discrepancies between backend and frontend implementations (use toEqual) (#110268)

**Highlights**

* **Single-version migrations**: add `targetVersion` to migrator & model, separate outputs, enforce exact version.
* **Datasource fixes**: include `apiVersion` in tests, empty-string → `{}`, preserve `{}` refs, drop unwanted defaults.
* **Panel defaults & nesting**: only top-level panels get defaults; preserve empty `transformations` context-aware; filter repeated panels.

* **Migration parity**

  * V16: collapsed rows, grid height parsing (`px`).
  * V17: omit `maxPerRow` when `minSpan=1`.
  * V19–V20: cleanup defaults (`targetBlank`, style).
  * V23–V24: template vars + table panel consistency.
  * V28: full singlestat/stat parity, mappings & color.
  * V30–V36: threshold logic, empty refs, nested targets.
* **Save-model cleanup**: replicate frontend defaults/filtering, drop null IDs, metadata, unused props.
* **Testing**: unified suites, dev dashboards (v42), full unit coverage for major migrations.

Co-authored-by: Ivan Ortega [ivanortegaalba@gmail.com](mailto:ivanortegaalba@gmail.com)
Co-authored-by: Dominik Prokop [dominik.prokop@grafana.com](mailto:dominik.prokop@grafana.com)

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

@@ -6,9 +6,39 @@ import (
 	"github.com/grafana/grafana/apps/dashboard/pkg/migration/schemaversion"
 )
 
-type TestDataSourceProvider struct{}
+// DataSourceConfig defines different test configurations
+type DataSourceConfig string
 
-func (m *TestDataSourceProvider) GetDataSourceInfo(_ context.Context) []schemaversion.DataSourceInfo {
+const (
+	// StandardTestConfig provides datasources for standard migration tests
+	StandardTestConfig DataSourceConfig = "standard"
+	// DevDashboardConfig provides datasources matching dev dashboard requirements
+	DevDashboardConfig DataSourceConfig = "dev-dashboard"
+)
+
+// ConfigurableDataSourceProvider provides flexible datasource configurations for different test scenarios
+type ConfigurableDataSourceProvider struct {
+	config DataSourceConfig
+}
+
+// NewDataSourceProvider creates a provider with the specified configuration
+func NewDataSourceProvider(config DataSourceConfig) *ConfigurableDataSourceProvider {
+	return &ConfigurableDataSourceProvider{config: config}
+}
+
+func (p *ConfigurableDataSourceProvider) GetDataSourceInfo(_ context.Context) []schemaversion.DataSourceInfo {
+	switch p.config {
+	case StandardTestConfig:
+		return p.getStandardTestDataSources()
+	case DevDashboardConfig:
+		return p.getDevDashboardDataSources()
+	default:
+		return p.getStandardTestDataSources()
+	}
+}
+
+// getStandardTestDataSources returns datasources for standard migration tests
+func (p *ConfigurableDataSourceProvider) getStandardTestDataSources() []schemaversion.DataSourceInfo {
 	return []schemaversion.DataSourceInfo{
 		{
 			Default:    true,
@@ -22,7 +52,7 @@ func (m *TestDataSourceProvider) GetDataSourceInfo(_ context.Context) []schemave
 			Default:    false,
 			UID:        "non-default-test-ds-uid",
 			Type:       "loki",
-			APIVersion: "1",
+			APIVersion: "v1",
 			Name:       "Non Default Test Datasource Name",
 			ID:         2,
 		},
@@ -61,7 +91,56 @@ func (m *TestDataSourceProvider) GetDataSourceInfo(_ context.Context) []schemave
 	}
 }
 
-// GetTestDataSourceProvider returns a singleton instance of the test provider
-func GetTestDataSourceProvider() *TestDataSourceProvider {
-	return &TestDataSourceProvider{}
+// getDevDashboardDataSources returns datasources for dev dashboard tests
+func (p *ConfigurableDataSourceProvider) getDevDashboardDataSources() []schemaversion.DataSourceInfo {
+	return []schemaversion.DataSourceInfo{
+		{
+			Default:    true,
+			UID:        "testdata-type-uid",
+			Type:       "grafana-testdata-datasource",
+			APIVersion: "v1",
+			Name:       "grafana-testdata-datasource",
+			ID:         1,
+		},
+		{
+			Default:    false,
+			UID:        "testdata",
+			Type:       "grafana-testdata-datasource",
+			APIVersion: "", // Frontend testdata datasource has no apiVersion
+			Name:       "TestData",
+			ID:         2,
+		},
+		{
+			Default:    false,
+			UID:        "prometheus-uid",
+			Type:       "prometheus",
+			APIVersion: "v1",
+			Name:       "Prometheus",
+			ID:         3,
+		},
+		{
+			Default:    false,
+			UID:        "loki-uid",
+			Type:       "loki",
+			APIVersion: "v1",
+			Name:       "Loki",
+			ID:         4,
+		},
+		{
+			Default:    false,
+			UID:        "elasticsearch-uid",
+			Type:       "elasticsearch",
+			APIVersion: "v1",
+			Name:       "Elasticsearch",
+			ID:         5,
+		},
+		{
+			Default:    false,
+			UID:        "-- Mixed --",
+			Type:       "mixed",
+			APIVersion: "v1",
+			Name:       "-- Mixed --",
+			ID:         6,
+		},
+	}
 }