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_test.go

@@ -0,0 +1,111 @@
+package testutil
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConfigurableDataSourceProvider(t *testing.T) {
+	ctx := context.Background()
+
+	t.Run("standard test config", func(t *testing.T) {
+		provider := NewDataSourceProvider(StandardTestConfig)
+		dataSources := provider.GetDataSourceInfo(ctx)
+
+		require.Len(t, dataSources, 6)
+
+		// Verify standard test configuration
+		defaultDS := dataSources[0]
+		assert.True(t, defaultDS.Default)
+		assert.Equal(t, "default-ds-uid", defaultDS.UID)
+		assert.Equal(t, "prometheus", defaultDS.Type)
+		assert.Equal(t, "v1", defaultDS.APIVersion)
+	})
+
+	t.Run("dev dashboard config", func(t *testing.T) {
+		provider := NewDataSourceProvider(DevDashboardConfig)
+		dataSources := provider.GetDataSourceInfo(ctx)
+
+		require.Len(t, dataSources, 6)
+
+		// Verify dev dashboard configuration
+		defaultDS := dataSources[0]
+		assert.True(t, defaultDS.Default)
+		assert.Equal(t, "testdata-type-uid", defaultDS.UID)
+		assert.Equal(t, "grafana-testdata-datasource", defaultDS.Type)
+		assert.Equal(t, "v1", defaultDS.APIVersion)
+
+		// Verify testdata without apiVersion
+		testDataDS := dataSources[1]
+		assert.False(t, testDataDS.Default)
+		assert.Equal(t, "testdata", testDataDS.UID)
+		assert.Equal(t, "grafana-testdata-datasource", testDataDS.Type)
+		assert.Equal(t, "", testDataDS.APIVersion) // No apiVersion for frontend testdata
+	})
+
+	t.Run("equivalent configurations", func(t *testing.T) {
+		// Test that different ways of creating providers return equivalent results
+		standardProvider1 := NewDataSourceProvider(StandardTestConfig)
+		standardProvider2 := NewDataSourceProvider(StandardTestConfig)
+		devProvider1 := NewDataSourceProvider(DevDashboardConfig)
+		devProvider2 := NewDataSourceProvider(DevDashboardConfig)
+
+		standardDS1 := standardProvider1.GetDataSourceInfo(ctx)
+		standardDS2 := standardProvider2.GetDataSourceInfo(ctx)
+		devDS1 := devProvider1.GetDataSourceInfo(ctx)
+		devDS2 := devProvider2.GetDataSourceInfo(ctx)
+
+		require.Len(t, standardDS1, 6)
+		require.Len(t, standardDS2, 6)
+		require.Len(t, devDS1, 6)
+		require.Len(t, devDS2, 6)
+
+		// Verify equivalent configurations return the same data
+		assert.Equal(t, standardDS1[0].UID, standardDS2[0].UID)
+		assert.Equal(t, devDS1[0].UID, devDS2[0].UID)
+		assert.Equal(t, "default-ds-uid", standardDS1[0].UID)
+		assert.Equal(t, "testdata-type-uid", devDS1[0].UID)
+	})
+
+	t.Run("unknown config defaults to standard", func(t *testing.T) {
+		provider := NewDataSourceProvider("unknown-config")
+		dataSources := provider.GetDataSourceInfo(ctx)
+
+		require.Len(t, dataSources, 6)
+
+		// Should default to standard configuration
+		defaultDS := dataSources[0]
+		assert.Equal(t, "default-ds-uid", defaultDS.UID)
+		assert.Equal(t, "prometheus", defaultDS.Type)
+	})
+}
+
+// TestModernUsageExample demonstrates how to use the new configurable approach
+func TestModernUsageExample(t *testing.T) {
+	// Example of modern usage in migration tests
+	t.Run("modern test setup", func(t *testing.T) {
+		// Create provider with specific configuration
+		provider := NewDataSourceProvider(StandardTestConfig)
+
+		// Use in migration initialization (example)
+		dataSources := provider.GetDataSourceInfo(context.Background())
+
+		// Verify we got the expected configuration
+		require.NotEmpty(t, dataSources)
+		assert.Equal(t, "prometheus", dataSources[0].Type)
+	})
+
+	t.Run("dev dashboard test setup", func(t *testing.T) {
+		// For dev dashboard tests
+		provider := NewDataSourceProvider(DevDashboardConfig)
+
+		dataSources := provider.GetDataSourceInfo(context.Background())
+
+		// Verify we got the dev dashboard configuration
+		require.NotEmpty(t, dataSources)
+		assert.Equal(t, "grafana-testdata-datasource", dataSources[0].Type)
+	})
+}