pkg/manager/diff: add tests

Refactor the package to support testing and add
a number of basic tests.

1 files changed, 223 insertions, 0 deletions

diff --git a/pkg/manager/diff/diff_test.go b/pkg/manager/diff/diff_test.go
new file mode 100644
index 000000000..3ac2cbfcb
--- /dev/null
+++ b/pkg/manager/diff/diff_test.go
@@ -0,0 +1,223 @@
+// Copyright 2026 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package diff
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/google/syzkaller/pkg/flatrpc"
+	"github.com/google/syzkaller/pkg/manager"
+	"github.com/google/syzkaller/pkg/mgrconfig"
+	"github.com/google/syzkaller/pkg/report"
+	"github.com/google/syzkaller/pkg/repro"
+	"github.com/google/syzkaller/prog"
+	_ "github.com/google/syzkaller/prog/test"
+	"github.com/google/syzkaller/vm"
+	"github.com/google/syzkaller/vm/dispatcher"
+)
+
+type testEnv struct {
+	t       *testing.T
+	ctx     context.Context
+	cancel  context.CancelFunc
+	diffCtx *diffContext
+	base    *MockKernel
+	new     *MockKernel
+	done    chan error
+}
+
+func newTestEnv(t *testing.T, cfg *Config) *testEnv {
+	if cfg == nil {
+		cfg = &Config{}
+	}
+	if cfg.Store == nil {
+		cfg.Store = &manager.DiffFuzzerStore{BasePath: t.TempDir()}
+	}
+	if cfg.PatchedOnly == nil {
+		cfg.PatchedOnly = make(chan *Bug, 1)
+	}
+	if cfg.BaseCrashes == nil {
+		cfg.BaseCrashes = make(chan string, 1)
+	}
+	if cfg.runner == nil {
+		// Default to a no-op runner if none provided.
+		cfg.runner = newMockRunner(nil)
+	}
+
+	diffCtx := &diffContext{
+		cfg:           *cfg,
+		doneRepro:     make(chan *manager.ReproResult, 1),
+		store:         cfg.Store,
+		reproAttempts: map[string]int{},
+		patchedOnly:   cfg.PatchedOnly,
+	}
+
+	base := &MockKernel{
+		CrashesCh: make(chan *report.Report, 1),
+		LoopFunc:  func(ctx context.Context) error { return nil },
+	}
+	newKernel := &MockKernel{
+		CrashesCh: make(chan *report.Report, 1),
+		LoopFunc:  func(ctx context.Context) error { return nil },
+	}
+
+	newKernel.PoolVal = dispatcher.NewPool[*vm.Instance](1, func(ctx context.Context, index int) (*vm.Instance, error) {
+		return &vm.Instance{}, nil
+	}, func(ctx context.Context, inst *vm.Instance, upd dispatcher.UpdateInfo) {
+	})
+	newKernel.ConfigVal = &mgrconfig.Config{}
+
+	diffCtx.base = base
+	diffCtx.new = newKernel
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	return &testEnv{
+		t:       t,
+		ctx:     ctx,
+		cancel:  cancel,
+		diffCtx: diffCtx,
+		base:    base,
+		new:     newKernel,
+		done:    make(chan error, 1),
+	}
+}
+
+func (env *testEnv) start() {
+	go func() {
+		env.done <- env.diffCtx.Loop(env.ctx)
+	}()
+}
+
+func (env *testEnv) close() {
+	env.cancel()
+	select {
+	case <-env.done:
+	case <-time.After(5 * time.Second):
+		env.t.Error("timeout waiting for diffCtx loop to exit")
+	}
+}
+
+func (env *testEnv) waitForStatus(title string, status manager.DiffBugStatus) {
+	env.t.Helper()
+	start := time.Now()
+	for time.Since(start) < 15*time.Second {
+		for _, bug := range env.diffCtx.store.List() {
+			if bug.Title == title && bug.Status == status {
+				return
+			}
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	env.t.Fatalf("timed out waiting for status: %s", status)
+}
+
+type MockKernel struct {
+	LoopFunc          func(ctx context.Context) error
+	CrashesCh         chan *report.Report
+	TriageProgressVal float64
+	ProgsPerAreaVal   map[string]int
+	CoverFiltersVal   manager.CoverageFilters
+	ConfigVal         *mgrconfig.Config
+	PoolVal           *vm.Dispatcher
+	FeaturesVal       flatrpc.Feature
+	ReporterVal       *report.Reporter
+}
+
+func (mk *MockKernel) Loop(ctx context.Context) error {
+	if mk.LoopFunc != nil {
+		return mk.LoopFunc(ctx)
+	}
+	<-ctx.Done()
+	return nil
+}
+
+func (mk *MockKernel) Crashes() <-chan *report.Report {
+	return mk.CrashesCh
+}
+
+func (mk *MockKernel) TriageProgress() float64 {
+	return mk.TriageProgressVal
+}
+
+func (mk *MockKernel) ProgsPerArea() map[string]int {
+	return mk.ProgsPerAreaVal
+}
+
+func (mk *MockKernel) CoverFilters() manager.CoverageFilters {
+	return mk.CoverFiltersVal
+}
+
+func (mk *MockKernel) Config() *mgrconfig.Config {
+	return mk.ConfigVal
+}
+
+func (mk *MockKernel) Pool() *vm.Dispatcher {
+	return mk.PoolVal
+}
+
+func (mk *MockKernel) Features() flatrpc.Feature {
+	return mk.FeaturesVal
+}
+
+func (mk *MockKernel) Reporter() *report.Reporter {
+	return mk.ReporterVal
+}
+
+func (mk *MockKernel) FinishCorpusTriage() {
+	mk.TriageProgressVal = 1.0
+}
+
+type mockRunner struct {
+	runFunc func(ctx context.Context, k Kernel, r *repro.Result, fullRepro bool) *reproRunnerResult
+	doneCh  chan reproRunnerResult
+}
+
+func newMockRunner(cb func(context.Context, Kernel, *repro.Result, bool) *reproRunnerResult) *mockRunner {
+	return &mockRunner{
+		runFunc: cb,
+		doneCh:  make(chan reproRunnerResult, 1),
+	}
+}
+
+func (m *mockRunner) Run(ctx context.Context, k Kernel, r *repro.Result, fullRepro bool) {
+	if m.runFunc != nil {
+		res := m.runFunc(ctx, k, r, fullRepro)
+		if res != nil {
+			m.doneCh <- *res
+		}
+	}
+}
+
+func (m *mockRunner) Results() <-chan reproRunnerResult {
+	return m.doneCh
+}
+
+func mockRepro(title string, err error) func(context.Context, []byte, repro.Environment) (
+	*repro.Result, *repro.Stats, error) {
+	return mockReproCallback(title, err, nil)
+}
+
+func mockReproCallback(title string, returnErr error,
+	callback func()) func(context.Context, []byte, repro.Environment) (
+	*repro.Result, *repro.Stats, error) {
+	return func(ctx context.Context, crashLog []byte, env repro.Environment) (*repro.Result, *repro.Stats, error) {
+		if callback != nil {
+			callback()
+		}
+		if returnErr != nil {
+			return nil, nil, returnErr
+		}
+		target, err := prog.GetTarget("test", "64")
+		if err != nil {
+			return nil, nil, err
+		}
+		return &repro.Result{
+			Report: &report.Report{Title: title},
+			Prog:   target.DataMmapProg(),
+		}, &repro.Stats{}, nil
+	}
+}