diff --git a/store_test.go b/store_test.go
index 5ecd5b1..44b3a7f 100644
--- a/store_test.go
+++ b/store_test.go
@@ -1,95 +1,263 @@
 package main
 
 import (
-	"database/sql"
-	"os"
+	"context"
+	"sort"
+	"strconv"
 	"testing"
-
-	_ "github.com/lib/pq"
+	"time"
 )
 
-// newTestStore opens a connection to the test DB, skipping if not available.
-// Pattern from go-htmx-web-dev skill: TDD mandatory, no code without tests.
-func newTestStore(t *testing.T) *Store {
+// fixedClock — deterministic clock for tests. Returns the same instant on every
+// call until advanced. Per the VOPR/Speckl constraint: no real time in tests.
+type fixedClock struct {
+	now time.Time
+}
+
+func (c *fixedClock) Now() time.Time { return c.now }
+
+func (c *fixedClock) Advance(d time.Duration) { c.now = c.now.Add(d) }
+
+// seqID — deterministic ID generator. Returns "id-1", "id-2", ... per call.
+// Per the VOPR/Speckl constraint: no random IDs in tests.
+type seqID struct {
+	n int
+}
+
+func (s *seqID) NewID() string {
+	s.n++
+	return idFor(s.n)
+}
+
+func idFor(n int) string {
+	return "id-" + itoa(n)
+}
+
+func itoa(n int) string {
+	if n == 0 {
+		return "0"
+	}
+	var buf [20]byte
+	i := len(buf)
+	for n > 0 {
+		i--
+		buf[i] = byte('0' + n%10)
+		n /= 10
+	}
+	return string(buf[i:])
+}
+
+// newTestStore — builds a Store with deterministic clock and ID generator.
+// Does NOT start the flush goroutine. Does NOT restore from disk.
+func newTestStore(t *testing.T) (*Store, *fixedClock, *seqID) {
 	t.Helper()
-	dsn := os.Getenv("POSTS_TEST_DSN")
-	if dsn == "" {
-		dsn = "postgres://posts:posts@127.0.0.1:5432/posts_test?sslmode=disable"
-	}
-	db, err := sql.Open("postgres", dsn)
-	if err != nil {
-		t.Skipf("no test db: %v", err)
-	}
-	if err := db.Ping(); err != nil {
-		t.Skipf("no test db: %v", err)
-	}
-	return NewStore(db)
+	clock := &fixedClock{now: time.Date(2026, 6, 22, 22, 0, 0, 0, time.UTC)}
+	ids := &seqID{}
+	s := NewStoreWithOptions(StoreOptions{
+		Now:           clock.Now,
+		NewID:         ids.NewID,
+		FlushInterval: 0, // no timer
+		FlushPath:     t.TempDir(),
+		StartFlush:    false,
+	})
+	// Bootstrap required authors + channels.
+	must(t, Submit(context.Background(), s, &UpsertAuthor{ID: "scott", AuthorKind: "human", DisplayName: "Scott"}))
+	must(t, Submit(context.Background(), s, &UpsertAuthor{ID: "hermes", AuthorKind: "agent", DisplayName: "Hermes"}))
+	must(t, Submit(context.Background(), s, &UpsertChannel{Slug: "scobleclaw", Name: "Scobleclaw"}))
+	must(t, Submit(context.Background(), s, &UpsertChannel{Slug: "agents", Name: "Agents"}))
+	return s, clock, ids
 }
 
-func TestCreatePostBumpsAt(t *testing.T) {
-	s := newTestStore(t)
-	p, err := s.CreatePost("scott", "Hello", "world", []string{"scobleclaw"})
+func must(t *testing.T, err error) {
+	t.Helper()
 	if err != nil {
-		t.Fatalf("create: %v", err)
-	}
-	if p.ID == "" {
-		t.Fatal("expected id")
-	}
-	if p.BumpedAt.IsZero() {
-		t.Fatal("expected bumped_at set")
+		t.Fatalf("submit: %v", err)
 	}
 }
 
-func TestAddCommentBumpsPost(t *testing.T) {
-	s := newTestStore(t)
-	p, err := s.CreatePost("scott", "Hello", "world", nil)
-	if err != nil {
-		t.Fatalf("create: %v", err)
+func TestCreatePost_AssignsIDAndBumpsAt(t *testing.T) {
+	s, clock, _ := newTestStore(t)
+	m := &CreatePost{AuthorID: "scott", Title: "Hello", Body: "world", Channels: []string{"scobleclaw"}}
+	if err := Submit(context.Background(), s, m); err != nil {
+		t.Fatalf("submit: %v", err)
 	}
-	before := p.BumpedAt
+	if m.ResolvedPostID() != "id-1" { // first real post is the 1st generated id (bootstrap uses supplied IDs)
+		t.Fatalf("expected id-1, got %q", m.ResolvedPostID())
+	}
+	p, ok := s.GetPost(m.ResolvedPostID())
+	if !ok {
+		t.Fatalf("post not found")
+	}
+	if !p.BumpedAt.Equal(clock.Now()) {
+		t.Fatalf("bumped_at mismatch: got %v, want %v", p.BumpedAt, clock.Now())
+	}
+}
 
-	// sleep a beat so timestamps are strictly different
-	// (we're testing logical correctness; in CI you'd inject a clock)
-	c, err := s.AddComment(p.ID, "", "hermes", "first!")
-	if err != nil {
+func TestAddComment_BumpsPost(t *testing.T) {
+	s, clock, _ := newTestStore(t)
+	cp := &CreatePost{AuthorID: "scott", Title: "Hello", Body: "world"}
+	if err := Submit(context.Background(), s, cp); err != nil {
+		t.Fatal(err)
+	}
+	beforeBump := s.posts[cp.ResolvedPostID()].BumpedAt
+
+	clock.Advance(2 * time.Minute)
+	ac := &AddComment{PostID: cp.ResolvedPostID(), AuthorID: "hermes", Body: "first!"}
+	if err := Submit(context.Background(), s, ac); err != nil {
 		t.Fatalf("add comment: %v", err)
 	}
-	if c.Path != c.ID {
-		t.Fatalf("top-level path should equal id, got %q", c.Path)
-	}
-
-	got, err := s.GetPost(p.ID)
-	if err != nil {
-		t.Fatalf("get: %v", err)
-	}
-	if !got.BumpedAt.After(before) && !got.BumpedAt.Equal(before) {
-		t.Fatalf("post should have been bumped, before=%v after=%v", before, got.BumpedAt)
+	got, _ := s.GetPost(cp.ResolvedPostID())
+	if !got.BumpedAt.After(beforeBump) {
+		t.Fatalf("post should have been bumped, before=%v after=%v", beforeBump, got.BumpedAt)
 	}
 }
 
 func TestNestedCommentPath(t *testing.T) {
-	s := newTestStore(t)
-	p, err := s.CreatePost("scott", "Tree test", "body", nil)
+	s, _, _ := newTestStore(t)
+	cp := &CreatePost{AuthorID: "scott", Title: "Tree", Body: "body"}
+	must(t, Submit(context.Background(), s, cp))
+	c1 := &AddComment{PostID: cp.ResolvedPostID(), AuthorID: "hermes", Body: "top"}
+	must(t, Submit(context.Background(), s, c1))
+	c2 := &AddComment{PostID: cp.ResolvedPostID(), ParentID: c1.ResolvedCommentID(), AuthorID: "hermes", Body: "nested"}
+	must(t, Submit(context.Background(), s, c2))
+	if c2.ResolvedDepth() != 1 {
+		t.Fatalf("expected depth 1, got %d", c2.ResolvedDepth())
+	}
+	if !startsWith(c2.ResolvedPath(), c1.ResolvedCommentID()+".") {
+		t.Fatalf("path %q should start with %q", c2.ResolvedPath(), c1.ResolvedCommentID()+".")
+	}
+}
+
+func TestSnapshot_RoundTrip(t *testing.T) {
+	s, _, _ := newTestStore(t)
+	cp := &CreatePost{AuthorID: "scott", Title: "P", Body: "B", Channels: []string{"scobleclaw"}}
+	must(t, Submit(context.Background(), s, cp))
+	ac := &AddComment{PostID: cp.ResolvedPostID(), AuthorID: "hermes", Body: "C"}
+	must(t, Submit(context.Background(), s, ac))
+
+	data, err := s.Snapshot()
 	if err != nil {
-		t.Fatal(err)
+		t.Fatalf("snapshot: %v", err)
 	}
-	c1, err := s.AddComment(p.ID, "", "hermes", "top")
-	if err != nil {
-		t.Fatal(err)
+	if len(data) < 100 {
+		t.Fatalf("snapshot too small: %d bytes", len(data))
 	}
-	c2, err := s.AddComment(p.ID, c1.ID, "hermes", "nested")
-	if err != nil {
-		t.Fatal(err)
+
+	s2 := NewStoreWithOptions(StoreOptions{
+		Now:           func() time.Time { return time.Date(2027, 1, 1, 0, 0, 0, 0, time.UTC) },
+		NewID:         func() string { return "restored" },
+		FlushInterval: 0,
+		FlushPath:     "/tmp",
+		StartFlush:    false,
+	})
+	if err := s2.Restore(data); err != nil {
+		t.Fatalf("restore: %v", err)
 	}
-	if c2.Depth != 1 {
-		t.Fatalf("expected depth 1, got %d", c2.Depth)
+	if _, ok := s2.GetPost(cp.ResolvedPostID()); !ok {
+		t.Fatalf("post not restored")
 	}
-	wantPrefix := c1.ID + "."
-	if !startsWith(c2.Path, wantPrefix) {
-		t.Fatalf("path %q should start with %q", c2.Path, wantPrefix)
+	comments := s2.ListComments(cp.ResolvedPostID())
+	if len(comments) != 1 {
+		t.Fatalf("expected 1 comment, got %d", len(comments))
 	}
 }
 
+func TestListPosts_FilteredByChannel(t *testing.T) {
+	s, _, _ := newTestStore(t)
+	p1 := &CreatePost{AuthorID: "scott", Body: "in scobleclaw", Channels: []string{"scobleclaw"}}
+	must(t, Submit(context.Background(), s, p1))
+	p2 := &CreatePost{AuthorID: "scott", Body: "in agents", Channels: []string{"agents"}}
+	must(t, Submit(context.Background(), s, p2))
+	got := s.ListPosts("scobleclaw", 10)
+	if len(got) != 1 {
+		t.Fatalf("expected 1 post in scobleclaw, got %d", len(got))
+	}
+	if got[0].ID != p1.ResolvedPostID() {
+		t.Fatalf("wrong post returned")
+	}
+}
+
+func TestListPosts_NewestBumpedFirst(t *testing.T) {
+	s, clock, _ := newTestStore(t)
+	p1 := &CreatePost{AuthorID: "scott", Body: "first"}
+	must(t, Submit(context.Background(), s, p1))
+	clock.Advance(time.Minute)
+	p2 := &CreatePost{AuthorID: "scott", Body: "second"}
+	must(t, Submit(context.Background(), s, p2))
+	got := s.ListPosts("", 10)
+	if len(got) != 2 {
+		t.Fatalf("expected 2 posts, got %d", len(got))
+	}
+	if got[0].ID != p2.ResolvedPostID() {
+		t.Fatalf("newest first failed: got %s, want %s", got[0].ID, p2.ResolvedPostID())
+	}
+}
+
+func TestValidation_FailsWithoutAuthor(t *testing.T) {
+	s, _, _ := newTestStore(t)
+	m := &CreatePost{AuthorID: "ghost", Body: "x"}
+	err := Submit(context.Background(), s, m)
+	if err == nil {
+		t.Fatalf("expected validation error for unknown author")
+	}
+}
+
+func TestValidation_FailsWithEmptyBody(t *testing.T) {
+	s, _, _ := newTestStore(t)
+	m := &CreatePost{AuthorID: "scott", Body: "   "}
+	err := Submit(context.Background(), s, m)
+	if err == nil {
+		t.Fatalf("expected validation error for empty body")
+	}
+}
+
+func TestMemUsage_ReportsNonZero(t *testing.T) {
+	s, _, _ := newTestStore(t)
+	cp := &CreatePost{AuthorID: "scott", Body: "x"}
+	must(t, Submit(context.Background(), s, cp))
+	mem := s.MemUsage()
+	if mem.Posts == 0 {
+		t.Fatalf("expected posts > 0, got %d", mem.Posts)
+	}
+	if mem.Authors == 0 {
+		t.Fatalf("expected authors > 0, got %d", mem.Authors)
+	}
+}
+
+func TestDeterminism_TwoRunsProduceIdenticalState(t *testing.T) {
+	runOnce := func() string {
+		s, clock, _ := newTestStore(t)
+		cp := &CreatePost{AuthorID: "scott", Title: "D", Body: "deterministic"}
+		must(t, Submit(context.Background(), s, cp))
+		c1 := &AddComment{PostID: cp.ResolvedPostID(), AuthorID: "hermes", Body: "c1"}
+		must(t, Submit(context.Background(), s, c1))
+		clock.Advance(time.Minute)
+		c2 := &AddComment{PostID: cp.ResolvedPostID(), ParentID: c1.ResolvedCommentID(), AuthorID: "hermes", Body: "c2"}
+		must(t, Submit(context.Background(), s, c2))
+		posts := s.ListPosts("", 10)
+		sort.Slice(posts, func(i, j int) bool { return posts[i].ID < posts[j].ID })
+		comments := s.ListComments(cp.ResolvedPostID())
+		sort.Slice(comments, func(i, j int) bool { return comments[i].ID < comments[j].ID })
+		return dump(cp.ResolvedPostID(), posts, comments)
+	}
+	a := runOnce()
+	b := runOnce()
+	if a != b {
+		t.Fatalf("non-deterministic:\n%s\nvs\n%s", a, b)
+	}
+}
+
+func dump(postID string, posts []*Post, comments []*Comment) string {
+	out := "post=" + postID + "\n"
+	for _, p := range posts {
+		out += "p:" + p.ID + ":" + p.BumpedAt.Format(time.RFC3339Nano) + "\n"
+	}
+	for _, c := range comments {
+		out += "c:" + c.ID + ":" + c.Path + ":" + strconv.Itoa(c.Depth) + "\n"
+	}
+	return out
+}
+
 func startsWith(s, prefix string) bool {
 	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
 }