Capture the fetch-with-base fixtures from mesh-catalog's code, and prove the checker whole against a real bus with fake build modules (issues 1679, 1287, 1288, 1289, 1678)

2026-10-21 21:23:22 +02:00
parent 96ba6bd3dc
commit 64599db3fa
6 changed files with 514 additions and 10 deletions
@@ -0,0 +1,497 @@
+//go:build integration
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats-server/v2/server"
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// busConf is the shape of the composed accounts file (mesh-controller internal/broker): one account with JetStream, the
+// controller's user and the checker's own principal <node>.<module>. It carries no per-principal permissions: the grants
+// the controller composes from the manifest's state and reads (only the checker writes its buckets) are the controller's,
+// and are proved by its own module check, not here.
+const busConf = `
+listen: 127.0.0.1:-1
+jetstream { store_dir: %q }
+accounts {
+  MESH {
+    jetstream: enabled
+    users = [
+      { user: "ctl", password: "pw" }
+      { user: "n1.mesh-delivery-checker", password: "pw" }
+    ]
+  }
+}
+`
+
+const (
+	repo   = "novox/mesh-delivery"
+	head1  = "1111111111111111111111111111111111111111"
+	head2  = "2222222222222222222222222222222222222222"
+	trunk  = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+	merged = "fedcba9876543210fedcba9876543210fedcba98" // the merge commit of the captured fetch answer
+	digU   = "aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11aa11"
+	digI   = "bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22bb22"
+)
+
+var captured = filepath.Join("..", "..", "internal", "check", "testdata", "captured")
+
+func readCaptured(t *testing.T, name string) map[string]any {
+	t.Helper()
+	raw, err := os.ReadFile(filepath.Join(captured, name+".json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var v map[string]any
+	if err := json.Unmarshal(raw, &v); err != nil {
+		t.Fatal(err)
+	}
+	return v
+}
+
+// fakeBuildModules serve the tools of mesh-build-go and mesh-build-node as the real ones do (ADR 0469 clause 2): a call on
+// mesh.mod.<module>.call.<tool>.<node>.<caller> answers at once with the step and its key, and the step's end is written to
+// the key <node>.<id> of the module's steps bucket. What the steps end with are the results the build modules' own code
+// marshalled (internal/check/testdata/captured, README).
+type fakeBuildModules struct {
+	js       jetstream.JetStream
+	ctx      context.Context
+	n        atomic.Int64
+	conflict atomic.Bool
+	mu       sync.Mutex
+	calls    map[string]int // by `<module>.<tool>`
+	testTool *testing.T
+}
+
+func (f *fakeBuildModules) count(tool string) int {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return f.calls[tool]
+}
+
+func (f *fakeBuildModules) result(t *testing.T, tool string, args map[string]any) json.RawMessage {
+	level, _ := args["level"].(string)
+	var v any
+	switch {
+	case strings.HasSuffix(tool, "_fetch"):
+		name := "go-fetch-clean"
+		if f.conflict.Load() {
+			name = "go-fetch-conflict"
+		}
+		fetched := readCaptured(t, name)
+		fetched["commit"], fetched["base"] = args["commit"], args["base"]
+		v = fetched
+	case strings.HasSuffix(tool, "_digest"):
+		d := map[string]string{"unit": digU, "integration": digI}[level]
+		v = map[string]any{"level": level, "packages": map[string]string{"fixture/slow": d}}
+	case strings.HasSuffix(tool, "_test"):
+		r := readCaptured(t, "go-test-slow")
+		r["level"] = level
+		v = r
+	}
+	data, _ := json.Marshal(v)
+	return data
+}
+
+func (f *fakeBuildModules) serve(t *testing.T, nc *nats.Conn, module string) {
+	steps, err := f.js.CreateKeyValue(f.ctx, jetstream.KeyValueConfig{Bucket: delivery.StepsBucket(module), History: 1})
+	if err != nil {
+		t.Fatal(err)
+	}
+	sub, err := nc.Subscribe("mesh.mod."+module+".call.>", func(m *nats.Msg) {
+		tokens := strings.Split(m.Subject, ".") // mesh mod <module> call <tool> <node> <caller>
+		tool, node := tokens[4], tokens[5]
+		f.mu.Lock()
+		f.calls[module+"."+tool]++
+		f.mu.Unlock()
+		var args map[string]any
+		_ = json.Unmarshal(m.Data, &args)
+		id := fmt.Sprintf("s%d", f.n.Add(1))
+		key, _ := delivery.StepKey(node, id)
+		put := func(s delivery.Step) {
+			data, err := delivery.EncodeStep(s)
+			if err == nil {
+				_, err = steps.Put(f.ctx, key, data)
+			}
+			if err != nil {
+				t.Errorf("writing step %s: %v", key, err)
+			}
+		}
+		step := delivery.Step{ID: id, Tool: tool, Node: node, State: delivery.StepRunning, Started: time.Now().UTC()}
+		put(step)
+		answer, _ := json.Marshal(map[string]any{"result": map[string]any{"step": id, "key": key, "state": "running"}, "error": "", "node": node})
+		_ = m.Respond(answer)
+		go func() {
+			time.Sleep(20 * time.Millisecond)
+			step.Ended = time.Now().UTC()
+			step.State, step.Result = delivery.StepPassed, f.result(t, tool, args)
+			put(step)
+		}()
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = sub.Unsubscribe() })
+}
+
+type bed struct {
+	ctx      context.Context
+	js       jetstream.JetStream
+	buckets  map[string]jetstream.KeyValue
+	tools    map[string]jetstream.KeyValue
+	fake     *fakeBuildModules
+	srvURL   string
+	announce []string
+	mu       sync.Mutex
+}
+
+// startBed starts the bus, the buckets the controller makes from the checker's and the other parts' manifests, the build
+// modules' streams and the checker's durable consumers on them, one node's toolchains, the gate's source naming the trunk, and
+// the fake build modules. It runs no checker.
+func startBed(t *testing.T) *bed {
+	dir, err := os.MkdirTemp(os.Getenv("TMPDIR"), "c")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { os.RemoveAll(dir) })
+	conf := filepath.Join(dir, "bus.conf")
+	if err := os.WriteFile(conf, []byte(fmt.Sprintf(busConf, filepath.Join(dir, "js"))), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	opts, err := server.ProcessConfigFile(conf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	opts.NoLog, opts.NoSigs = true, true
+	srv, err := server.NewServer(opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+	go srv.Start()
+	if !srv.ReadyForConnections(10 * time.Second) {
+		t.Fatal("the bus did not come up")
+	}
+	t.Cleanup(srv.Shutdown)
+	ctl, err := nats.Connect(srv.ClientURL(), nats.UserInfo("ctl", "pw"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(ctl.Close)
+	js, err := jetstream.New(ctl)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	t.Cleanup(cancel)
+	b := &bed{ctx: ctx, js: js, buckets: map[string]jetstream.KeyValue{}, tools: map[string]jetstream.KeyValue{}, srvURL: srv.ClientURL()}
+	for module, stream := range toolchainStreams {
+		if _, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: stream, Subjects: []string{"mesh.stream." + module + ".event.toolchain.reported"}}); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := js.CreateOrUpdateConsumer(ctx, stream, jetstream.ConsumerConfig{Durable: "n1_mesh-delivery-checker", AckPolicy: jetstream.AckExplicitPolicy}); err != nil {
+			t.Fatal(err)
+		}
+		kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: delivery.ToolchainsBucket(module), History: 1})
+		if err != nil {
+			t.Fatal(err)
+		}
+		b.tools[module] = kv
+	}
+	// The checker's stream of events, which the indexer and the forge bridge hear.
+	if _, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: "CHECKS", Subjects: []string{"mesh.stream.mesh-delivery-checker.event.>"}}); err != nil {
+		t.Fatal(err)
+	}
+	for name, history := range map[string]int{delivery.CheckerVerdictsBucket: delivery.CheckerVerdictsHistory, delivery.CheckerKeptBucket: delivery.CheckerKeptHistory,
+		delivery.CheckerOwedBucket: delivery.CheckerOwedHistory, delivery.PreviewsBucket: delivery.PreviewsHistory, delivery.CandidatesBucket: delivery.CandidatesHistory,
+		delivery.ModulesBucket: delivery.ModulesHistory, delivery.ManifestsBucket: delivery.ManifestsHistory, delivery.SourceBucket: delivery.SourceHistory,
+		delivery.PresenceBucket: delivery.PresenceHistory, delivery.HaveBucket: delivery.HaveHistory} {
+		kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: name, History: uint8(history)})
+		if err != nil {
+			t.Fatal(err)
+		}
+		b.buckets[name] = kv
+	}
+	b.setOnline(t, "n1", true)
+	for _, module := range []string{"mesh-build-go", "mesh-build-node"} {
+		b.setHealth(t, "n1", module)
+	}
+	b.fake = &fakeBuildModules{js: js, ctx: ctx, calls: map[string]int{}}
+	b.fake.serve(t, ctl, "mesh-build-go")
+	b.fake.serve(t, ctl, "mesh-build-node")
+	b.report(t, "mesh-build-go", "n1", "go", "go1.27.1", "1")
+	b.report(t, "mesh-build-node", "n1", "typescript", "tsc5", "1")
+	b.setTrunk(t, map[string]string{repo: trunk})
+	return b
+}
+
+func (b *bed) setTrunk(t *testing.T, heads map[string]string) {
+	t.Helper()
+	data, err := delivery.EncodeSource(delivery.Source{Group: "g", Heads: heads})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := b.buckets[delivery.SourceBucket].Put(b.ctx, delivery.SourceMainKey, data); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (b *bed) setOnline(t *testing.T, node string, online bool) {
+	t.Helper()
+	data, _ := delivery.EncodePresence(delivery.Presence{Online: online})
+	if _, err := b.buckets[delivery.PresenceBucket].Put(b.ctx, node, data); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (b *bed) setHealth(t *testing.T, node, module string) {
+	t.Helper()
+	data, err := delivery.EncodeHave(delivery.Have{Phase: delivery.PhaseRunning, Health: delivery.HealthOK})
+	if err != nil {
+		t.Fatal(err)
+	}
+	key, _ := delivery.HaveKey(node, module)
+	if _, err := b.buckets[delivery.HaveBucket].Put(b.ctx, key, data); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func (b *bed) report(t *testing.T, module, node, language, version, recipe string) {
+	t.Helper()
+	data, err := delivery.EncodeToolchain(delivery.Toolchain{Language: language, Version: version, Recipe: recipe, At: time.Now().UTC()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	key, _ := delivery.ToolchainKey(node, language)
+	if _, err := b.tools[module].Put(b.ctx, key, data); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := b.js.Publish(b.ctx, "mesh.stream."+module+".event.toolchain.reported", []byte(`{}`)); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// candidate writes candidates.<group> as the indexer does (the SDK's EncodeCandidate is the indexer's own encoder).
+func (b *bed) candidate(t *testing.T, group string, pulls ...delivery.CandidatePull) string {
+	t.Helper()
+	heads := make([]delivery.Head, len(pulls))
+	for i, p := range pulls {
+		heads[i] = p.Head
+	}
+	hash, err := delivery.HeadsHash(heads)
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := delivery.EncodeCandidate(delivery.Candidate{V: delivery.Version, Group: group, HeadsHash: hash, Pulls: pulls, FPSet: delivery.FingerprintSet(pulls)})
+	if err != nil {
+		t.Fatal(err)
+	}
+	key, _ := delivery.CandidatesKey(group)
+	if _, err := b.buckets[delivery.CandidatesBucket].Put(b.ctx, key, data); err != nil {
+		t.Fatal(err)
+	}
+	vk, _ := delivery.CheckerVerdictKey(group, hash)
+	return vk
+}
+
+func pull(repository string, number int, head string) delivery.CandidatePull {
+	return delivery.CandidatePull{Head: delivery.Head{Repository: repository, Number: number, Head: head}, Modules: []string{}}
+}
+
+// start runs the program as the checker of a node.
+func (b *bed) start(t *testing.T, env map[string]string) {
+	t.Helper()
+	broker := filepath.Join(t.TempDir(), "broker")
+	cred, _ := json.Marshal(credential{URL: b.srvURL, Node: "n1", Module: "mesh-delivery-checker", User: "n1.mesh-delivery-checker", Password: "pw"})
+	if err := os.WriteFile(broker, cred, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	e := map[string]string{"MESH_BROKER_FILE": broker}
+	for k, v := range env {
+		e[k] = v
+	}
+	runCtx, stop := context.WithCancel(b.ctx)
+	done := make(chan error, 1)
+	go func() { done <- run(runCtx, func(k string) string { return e[k] }, io.Discard) }()
+	t.Cleanup(func() { stop(); <-done })
+}
+
+// verdict reads the verdict key until pred holds of it, within 20 s.
+func (b *bed) verdict(t *testing.T, key string, pred func(delivery.Verdict) bool) delivery.Verdict {
+	t.Helper()
+	var last delivery.Verdict
+	for deadline := time.Now().Add(20 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+		e, err := b.buckets[delivery.CheckerVerdictsBucket].Get(b.ctx, key)
+		if err != nil {
+			continue
+		}
+		if last, err = delivery.DecodeVerdict(e.Value()); err == nil && pred(last) {
+			return last
+		}
+	}
+	t.Fatalf("verdicts.%s = %+v within 20 s", key, last)
+	return last
+}
+
+func ended(v delivery.Verdict) bool { return v.State != delivery.VerdictRunning }
+
+// owed reads the status the checker owes on a head.
+func (b *bed) owed(t *testing.T, number int, head, state string) delivery.Owed {
+	t.Helper()
+	key, err := delivery.CheckerOwedKey(repo, number, head)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var last delivery.Owed
+	for deadline := time.Now().Add(20 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+		e, err := b.buckets[delivery.CheckerOwedBucket].Get(b.ctx, key)
+		if err != nil {
+			continue
+		}
+		if last, err = delivery.DecodeCheckerOwed(e.Value()); err == nil && last.State == state {
+			return last
+		}
+	}
+	t.Fatalf("owed.%s = %+v within 20 s, want the state %s", key, last, state)
+	return last
+}
+
+// TestCheckerJudgesACandidateAndOwesItsStatus: a candidate the indexer wrote, one pull request of mesh-delivery, is fetched
+// merged onto the trunk the gate names, digested and tested at both levels on the node, kept, previewed; the verdict passes
+// with the counts of both levels and the composition not run, and the status mesh/check is owed on the head as success.
+func TestCheckerJudgesACandidateAndOwesItsStatus(t *testing.T) { // N6/AC5, 1300/AC5, 1445/AC1
+	b := startBed(t)
+	key := b.candidate(t, "feat/x", pull(repo, 7, head1))
+	b.start(t, nil)
+	v := b.verdict(t, key, ended)
+	if v.State != delivery.VerdictPass || v.Levels[delivery.LevelUnit].Run != 2 || v.Levels[delivery.LevelIntegration].Run != 2 || v.Trunk[repo] != trunk {
+		t.Fatalf("verdict = %+v", v)
+	}
+	if v.Composition == nil || v.Composition.State != delivery.CompositionNotRun || len(v.Machines) != 1 || v.Machines[0] != "n1" {
+		t.Errorf("composition %+v machines %v", v.Composition, v.Machines)
+	}
+	o := b.owed(t, 7, head1, "success")
+	if o.Context != delivery.StatusContextCheck || !strings.HasPrefix(o.Text, "pass 111111111111 on aaaaaaaaaaaa") || !strings.Contains(o.Text, "unit 2 run, 0 kept") {
+		t.Errorf("owed = %+v", o)
+	}
+	for tool, want := range map[string]int{"mesh-build-go.build_go_fetch": 1, "mesh-build-go.build_go_digest": 2, "mesh-build-go.build_go_test": 2} {
+		if got := b.fake.count(tool); got != want {
+			t.Errorf("%s called %d times, want %d", tool, got, want)
+		}
+	}
+	// What passed is kept once under each level's digest.
+	for _, k := range []string{"unit." + digU, "integration." + digI} {
+		if _, err := b.buckets[delivery.CheckerKeptBucket].Get(b.ctx, k); err != nil {
+			t.Errorf("kept.%s: %v", k, err)
+		}
+	}
+	// The preview of the head merged onto the trunk, with the tree and the manifest digest the fetch named.
+	pk, _ := delivery.PreviewKey(repo, head1, trunk)
+	e, err := b.buckets[delivery.PreviewsBucket].Get(b.ctx, pk)
+	if err != nil {
+		t.Fatalf("previews.%s: %v", pk, err)
+	}
+	pv, err := delivery.DecodePreview(e.Value())
+	if err != nil || pv.Merge != merged || pv.Modules["modules/m"].Tree != "1111111111111111111111111111111111111111" {
+		t.Errorf("preview = %+v, %v", pv, err)
+	}
+}
+
+// TestACheckOfEqualInputsRunsNothing: a second candidate (another head, the same digests) is checked with every package
+// taken from the first's kept verdicts: no test step runs and no second kept key appears.
+func TestACheckOfEqualInputsRunsNothing(t *testing.T) { // 1287/AC5, 1288/AC6
+	b := startBed(t)
+	first := b.candidate(t, "feat/x", pull(repo, 7, head1))
+	b.start(t, nil)
+	b.verdict(t, first, ended)
+	tests, kept := b.fake.count("mesh-build-go.build_go_test"), keptCount(t, b)
+	second := b.candidate(t, "feat/y", pull(repo, 8, head2))
+	v := b.verdict(t, second, ended)
+	if v.State != delivery.VerdictPass || v.Levels[delivery.LevelUnit].Run != 0 || v.Levels[delivery.LevelUnit].Kept != 2 || v.Levels[delivery.LevelIntegration].Run != 0 {
+		t.Fatalf("verdict = %+v, want everything taken from the kept verdicts", v)
+	}
+	if got := b.fake.count("mesh-build-go.build_go_test"); got != tests {
+		t.Errorf("build_go_test called %d times, was %d: a test ran for equal inputs", got, tests)
+	}
+	if got := keptCount(t, b); got != kept {
+		t.Errorf("%d kept keys, was %d", got, kept)
+	}
+}
+
+func keptCount(t *testing.T, b *bed) int {
+	t.Helper()
+	keys, err := b.buckets[delivery.CheckerKeptBucket].Keys(b.ctx)
+	if err != nil {
+		return 0
+	}
+	return len(keys)
+}
+
+// TestAHeadThatDoesNotMergeFailsNamingTheFilesAndRunsNoTest: the fetch answers the files in conflict; the verdict fails naming
+// them, no test or digest step is run, no preview is written and the status is owed as failure.
+func TestAHeadThatDoesNotMergeFailsNamingTheFilesAndRunsNoTest(t *testing.T) { // 1289/AC4
+	b := startBed(t)
+	b.fake.conflict.Store(true)
+	key := b.candidate(t, "feat/x", pull(repo, 7, head1))
+	b.start(t, nil)
+	v := b.verdict(t, key, ended)
+	if v.State != delivery.VerdictFail || !strings.Contains(v.Failed.Words, "files in conflict: a.go, sub/b.go") {
+		t.Fatalf("verdict = %+v", v)
+	}
+	if o := b.owed(t, 7, head1, "failure"); !strings.HasPrefix(o.Text, "failed: n1: ") || !strings.Contains(o.Text, "files in conflict: a.go, sub/b.go") {
+		t.Errorf("owed = %+v", o)
+	}
+	if n := b.fake.count("mesh-build-go.build_go_digest") + b.fake.count("mesh-build-go.build_go_test"); n != 0 {
+		t.Errorf("%d digest and test steps ran after a conflict", n)
+	}
+	if keys, _ := b.buckets[delivery.PreviewsBucket].Keys(b.ctx); len(keys) != 0 {
+		t.Errorf("previews %v for a head that does not merge", keys)
+	}
+}
+
+// TestAnHqPullRequestGetsNoVerdictAndAnotherDoes: hq's pull request is judged by no one (ADR 0484 clause 8), the other one in
+// the same run is.
+func TestAnHqPullRequestGetsNoVerdictAndAnotherDoes(t *testing.T) { // ADR 0484 clause 8
+	b := startBed(t)
+	hq := b.candidate(t, "feat/hq", pull("novox/hq", 3, head1))
+	other := b.candidate(t, "feat/x", pull(repo, 7, head2))
+	b.start(t, nil)
+	b.verdict(t, other, ended)
+	if _, err := b.buckets[delivery.CheckerVerdictsBucket].Get(b.ctx, hq); err == nil {
+		t.Error("hq's pull request has a verdict")
+	}
+}
+
+// TestACheckLeftRunningIsTakenOverWhenTheCheckerStarts: the verdict key holds running, left by a checker that stopped; the
+// started checker judges it again and ends it (ADR 0478 clause 6, as the builder's).
+func TestACheckLeftRunningIsTakenOverWhenTheCheckerStarts(t *testing.T) { // N6/AC2
+	b := startBed(t)
+	key := b.candidate(t, "feat/x", pull(repo, 7, head1))
+	group, heads, _ := delivery.ParseCheckerVerdictKey(key)
+	left, err := delivery.EncodeVerdict(delivery.Verdict{Group: group, Heads: heads, Trunk: map[string]string{repo: trunk}, State: delivery.VerdictRunning})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := b.buckets[delivery.CheckerVerdictsBucket].Create(b.ctx, key, left); err != nil {
+		t.Fatal(err)
+	}
+	b.start(t, nil)
+	if v := b.verdict(t, key, ended); v.State != delivery.VerdictPass {
+		t.Errorf("verdict = %+v", v)
+	}
+}
@@ -116,8 +116,8 @@ type bench struct {
 // the captured slow fixture's result at both levels, on shanks.
 func newBench(t testing.TB) *bench {
 	b := &bench{steps: &fakeSteps{}, kept: newMemKV(), prev: newMemKV()}
-	b.fetch = Fetched{Workspace: "ws1", Commit: head1, Modules: []string{"."}, Base: trunkA, Merge: "9999999999999999999999999999999999999999",
-		Changed: []string{"README.md"}}
+	b.fetch = captured[Fetched](t, "go-fetch-clean")
+	b.fetch.Modules, b.fetch.Changed, b.fetch.Trees = []string{"."}, []string{"README.md"}, nil
 	one := captured[Digested](t, "go-digest")
 	b.digest = map[string]Digested{
 		delivery.LevelUnit:        {Level: "unit", Packages: map[string]string{"fixture/slow": digA}},
@@ -268,9 +268,9 @@ func TestAReAskRunsOnlyWhatFailedAndWhatChanged(t *testing.T) { // 1288/AC2, AC3
 func TestANodePackageIsNeverKeptAndRunsEveryCheck(t *testing.T) { // 1288/AC4, 1292/AC1
 	b := newBench(t)
 	b.ex.Modules = langs{repoA: {buildrun.NodeBuildModule}}
-	b.fetch.Modules = []string{"modules/ui"}
+	b.fetch = captured[Fetched](t, "node-fetch-clean")
 	b.test = func(c stepCall) (any, error) {
-		return Tested{Level: c.args["level"].(string), Module: "modules/ui", Passed: true, Elapsed: 0.4, Bound: 5}, nil
+		return Tested{Level: c.args["level"].(string), Module: "modules/m", Passed: true, Elapsed: 0.4, Bound: 5}, nil
 	}
 	cs := caseOf(t, pullOf(repoA, 7, head1))
 	for i := 0; i < 2; i++ {
@@ -338,10 +338,10 @@ func TestTheChangesOwnPassingTestRunsFirstAndTheRestFollow(t *testing.T) { // 12

 func TestAHeadThatDoesNotMergeEndsFailedNamingTheFilesAndRunsNoTest(t *testing.T) { // 1289/AC4
 	b := newBench(t)
-	b.fetch = Fetched{Workspace: "ws1", Commit: head1, Base: trunkA, Conflicts: []string{"go.mod", "internal/x.go"}}
+	b.fetch = captured[Fetched](t, "go-fetch-conflict")
 	out := b.judge(t, caseOf(t, pullOf(repoA, 7, head1)))
 	f := out.Verdict.Failed
-	if out.Verdict.State != delivery.VerdictFail || f.Machine != "shanks" || !strings.Contains(f.Words, "files in conflict: go.mod, internal/x.go") {
+	if out.Verdict.State != delivery.VerdictFail || f.Machine != "shanks" || !strings.Contains(f.Words, "files in conflict: a.go, sub/b.go") {
 		t.Fatalf("verdict = %+v", out.Verdict)
 	}
 	if n := len(b.steps.tool("digest")) + len(b.steps.tool("test")); n != 0 {
@@ -483,7 +483,7 @@ func TestACleanMergeWritesItsPreviewWithTheTreesManifestsAndLocks(t *testing.T)

 func TestAHeadThatDoesNotMergeWritesNoPreview(t *testing.T) { // 1445/AC5
 	b := newBench(t)
-	b.fetch = Fetched{Workspace: "ws1", Commit: head1, Base: trunkA, Conflicts: []string{"go.mod"}}
+	b.fetch = captured[Fetched](t, "go-fetch-conflict")
 	b.judge(t, caseOf(t, pullOf(repoA, 7, head1)))
 	if len(b.prev.vals) != 0 {
 		t.Errorf("previews %v written for a head that does not merge", b.prev.vals)
@@ -4,6 +4,10 @@ test beside the module's test_test.go and digest_test.go (workspaceFor + runUnit
 slow and empty, and digestFixture + digests on testdata/repos/digest) at mesh-catalog origin/main cdbdb474, captured on
 2026-10-21 for issue 1679 and not kept there. The fixtures' package names are the build module's own (fixture/failing/bad...).

-The fields a fetch with a base adds (base, merge, conflicts, changed, trees) are the contract the lead relayed to the
-mesh-catalog agent (ADR 0484 clause 3, 2026-10-21); mesh-catalog's fetch step is not on main yet, so the fetch fixtures in
-the tests are written from that contract and are to be replaced by a capture once its fetch_test can marshal one.
+go-fetch-clean.json and go-fetch-conflict.json are what mesh-build-go's fetch step ends with (FetchResult, cmd/mesh-build-go
+fetch.go and preview.go) for a fetch with a base, the Result bytes of the step in mesh-catalog's own tests
+TestFetchWithABaseMergesAndAnswersThePreview and TestFetchWithAConflictEndsPassedAndNamesTheFiles (preview_test.go), copied
+into a throwaway test that wrote them out, at mesh-catalog feat/r4c5-checker d5804927 (the git commands are the test's fake,
+so the shas are its constants; the shape and the field names are the module's own marshalling). node-fetch-clean.json is the
+FetchResult json.Marshal of mesh-build-node's fetch (fetch.go, preview.go) in its test TestFetchWithABaseMergesAndAnswersThePreview
+(cmd/mesh-build-node/preview_test.go) at the same commit. Captured on 2026-10-21 for issue 1679.
@@ -0,0 +1 @@
+{"workspace":"mvii1iwu5414e4","commit":"0123456789abcdef0123456789abcdef01234567","modules":["."],"base":"abcdef0123456789abcdef0123456789abcdef01","merge":"fedcba9876543210fedcba9876543210fedcba98","changed":["a.go","modules/m/main.go"],"trees":{"modules/m":{"tree":"1111111111111111111111111111111111111111","manifest":"ca3d163bab055381827226140568f3bef7eaac187cebd76878e0b63e9e442356","locks":{"go.sum":"c5fc83c01e92404452b986527d239140ccf9a48b88e0c268fbf38c2e1429e9c9"}}}}
@@ -0,0 +1 @@
+{"workspace":"mvii1iwz5050eb","commit":"0123456789abcdef0123456789abcdef01234567","modules":["."],"base":"abcdef0123456789abcdef0123456789abcdef01","conflicts":["a.go","sub/b.go"]}
@@ -0,0 +1 @@
+{"workspace":"mvii1sxt979f67","commit":"0123456789abcdef0123456789abcdef01234567","modules":["modules/m"],"installed":[],"refused":[],"base":"abcdef0123456789abcdef0123456789abcdef01","merge":"0123456789abcdef0123456789abcdef01234567","changed":["modules/m/package.json"],"trees":{"modules/m":{"tree":"0123456789abcdef0123456789abcdef01234567","manifest":"0581b699d9d05517e69b21f5cedbeb2eee8aba2b205280b561be731594d7feef"}}}
				`@@ -0,0 +1 @@`
				`{"workspace":"mvii1iwu5414e4","commit":"0123456789abcdef0123456789abcdef01234567","modules":["."],"base":"abcdef0123456789abcdef0123456789abcdef01","merge":"fedcba9876543210fedcba9876543210fedcba98","changed":["a.go","modules/m/main.go"],"trees":{"modules/m":{"tree":"1111111111111111111111111111111111111111","manifest":"ca3d163bab055381827226140568f3bef7eaac187cebd76878e0b63e9e442356","locks":{"go.sum":"c5fc83c01e92404452b986527d239140ccf9a48b88e0c268fbf38c2e1429e9c9"}}}}`
				`@@ -0,0 +1 @@`
				`{"workspace":"mvii1iwz5050eb","commit":"0123456789abcdef0123456789abcdef01234567","modules":["."],"base":"abcdef0123456789abcdef0123456789abcdef01","conflicts":["a.go","sub/b.go"]}`
				`@@ -0,0 +1 @@`
				`{"workspace":"mvii1sxt979f67","commit":"0123456789abcdef0123456789abcdef01234567","modules":["modules/m"],"installed":[],"refused":[],"base":"abcdef0123456789abcdef0123456789abcdef01","merge":"0123456789abcdef0123456789abcdef01234567","changed":["modules/m/package.json"],"trees":{"modules/m":{"tree":"0123456789abcdef0123456789abcdef01234567","manifest":"0581b699d9d05517e69b21f5cedbeb2eee8aba2b205280b561be731594d7feef"}}}`