PR FIXUP - Boost change detector initial subtest speed

tests/change_detector/change_detector_test.go

@@ -20,6 +20,7 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+	"sync/atomic"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -59,14 +60,27 @@ func TestChanges(t *testing.T) {
 		sourceRepoPkgMap[pkg] = true
 	}
 
+	hasRunOnce := &atomic.Bool{}
+
 	for _, pkg := range targetRepoPkgList {
 		pkgName := strings.TrimPrefix(pkg, "github.com/sourcenetwork/defradb/")
 		t.Run(pkgName, func(t *testing.T) {
 			if pkg == "" || !sourceRepoPkgMap[pkg] {
 				t.Skip("skipping unknown or new test package")
 			}
 
-			t.Parallel()
+			if hasRunOnce.Load() {
+				// The first test runs very slowly, and if multiple tests are running concurrently
+				// all will be affected and the costs multiplied. It seems likely that this is
+				// compilation related, but that is not yet proven.
+				//
+				// Because of this the first sub-test will run on it's own, followed by the rest
+				// running in parallel.
+				t.Parallel()
+			} else {
+				hasRunOnce.Swap(true)
+			}
+
 			dataDir := t.TempDir()
 
 			sourceTestPkg := filepath.Join(sourceRepoDir, pkgName)