chore: use a more realistic change detection benchmark. (#1912)

benchmarks/changed/changed_bench_test.go

@@ -22,20 +22,46 @@ func BenchmarkChangeDetection(b *testing.B) {
 	const nstacks = 10
 
 	s := sandbox.New(b)
-	layout := []string{}
+	layout := []string{
+		"f:modules/common/common-1/main.tf:# nothing",
+		"f:modules/common/common-2/main.tf:# nothing",
+		"f:modules/common/common-3/main.tf:# nothing",
+	}
+
 	for i := 0; i < nstacks; i++ {
 		layout = append(layout, fmt.Sprintf("f:modules/mod-%d/main.tf:%s", i, "# nothing here"))
 		layout = append(layout, fmt.Sprintf("s:stack-%d", i))
-		layout = append(layout, fmt.Sprintf("f:stack-%d/main.tf:%s", i, Block("module",
-			Labels("something"),
-			Str("source", fmt.Sprintf("../modules/mod-%d", i)),
+		layout = append(layout, fmt.Sprintf("f:stack-%d/main.tf:%s", i, Doc(
+			Block("module",
+				Labels("something"),
+				Str("source", fmt.Sprintf("../modules/mod-%d", i)),
+			),
 		).String()))
+
+		// only even stacks has the common modules
+		if i%2 == 0 {
+			layout = append(layout, fmt.Sprintf("f:stack-%d/use-common.tf:%s", i, Doc(
+				Block("module",
+					Labels("common_mod1"),
+					Str("source", "../modules/common/common-1"),
+				),
+				Block("module",
+					Labels("common_mod2"),
+					Str("source", "../modules/common/common-2"),
+				),
+				Block("module",
+					Labels("common_mod3"),
+					Str("source", "../modules/common/common-3"),
+				),
+			)))
+		}
 	}
 	s.BuildTree(layout)
 	s.Git().CommitAll("create repo")
 	s.Git().Push("main")
 	s.Git().CheckoutNew("modify-some-modules")
 	test.WriteFile(b, filepath.Join(s.RootDir(), fmt.Sprintf("modules/mod-%d", nstacks-1)), "main.tf", "# modified")
+	test.WriteFile(b, filepath.Join(s.RootDir(), "modules/common/common-3"), "main.tf", "# modified")
 	s.Git().CommitAll("module modified")
 
 	manager := stack.NewGitAwareManager(s.Config(), s.Git().Unwrap())
@@ -44,8 +70,14 @@ func BenchmarkChangeDetection(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		report, err := manager.ListChanged(stack.ChangeConfig{BaseRef: "origin/main"})
 		assert.NoError(b, err)
-		assert.EqualInts(b, 1, len(report.Stacks))
-		assert.EqualStrings(b, fmt.Sprintf("/stack-%d", nstacks-1), report.Stacks[0].Stack.Dir.String())
+		assert.EqualInts(b, 6, len(report.Stacks))
+
+		assert.EqualStrings(b, "/stack-0", report.Stacks[0].Stack.Dir.String())
+		assert.EqualStrings(b, "/stack-2", report.Stacks[1].Stack.Dir.String())
+		assert.EqualStrings(b, "/stack-4", report.Stacks[2].Stack.Dir.String())
+		assert.EqualStrings(b, "/stack-6", report.Stacks[3].Stack.Dir.String())
+		assert.EqualStrings(b, "/stack-8", report.Stacks[4].Stack.Dir.String())
+		assert.EqualStrings(b, fmt.Sprintf("/stack-%d", nstacks-1), report.Stacks[5].Stack.Dir.String())
 	}
 }