diff --git a/internal/verifier/llm_test.go b/internal/verifier/llm_test.go
new file mode 100644
index 0000000..686ebcd
--- /dev/null
+++ b/internal/verifier/llm_test.go
@@ -0,0 +1,140 @@
+package verifier
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/priyanshujain/sanderling/internal/hierarchy"
+)
+
+// candidateTreeJSON is a small screen with one clickable button, one editable
+// field, and one scrollable list. Every node has positive bounds, so each is
+// additionally a swipe origin.
+const candidateTreeJSON = `{
+  "attributes": {"bounds": "[0,0,1080,2400]"},
+  "children": [
+    {"attributes": {"resource-id": "LoginSubmit", "text": "Sign in", "bounds": "[0,100,1080,200]"}, "clickable": true, "enabled": true, "children": []},
+    {"attributes": {"resource-id": "EmailField", "class": "EditText", "bounds": "[0,300,1080,400]"}, "enabled": true, "children": []},
+    {"attributes": {"resource-id": "List", "scrollable": "true", "bounds": "[0,500,1080,2000]"}, "children": []}
+  ]
+}`
+
+func TestAllCandidatesUnionsVerbsWithIndicesAndLabels(t *testing.T) {
+	tree, err := hierarchy.Parse(candidateTreeJSON)
+	if err != nil {
+		t.Fatal(err)
+	}
+	v := &Verifier{lastTree: tree}
+	candidates := v.AllCandidates()
+
+	// Indices are dense and ordered.
+	for i, candidate := range candidates {
+		if candidate.Index != i {
+			t.Errorf("candidate %d has Index %d", i, candidate.Index)
+		}
+	}
+
+	// Collect verbs per label to assert the union without pinning swipe count.
+	byLabel := map[string][]string{}
+	for _, candidate := range candidates {
+		byLabel[candidate.Label] = append(byLabel[candidate.Label], candidate.Verb)
+	}
+
+	// The clickable button is tap/doubleTap/longPress + swipe; its label is the
+	// visible text, not the resource-id.
+	submit := byLabel["Sign in"]
+	if !contains(submit, "taps") || !contains(submit, "doubleTaps") || !contains(submit, "longPresses") {
+		t.Errorf("Sign in verbs = %v, want tap family", submit)
+	}
+	if !contains(submit, "swipes") {
+		t.Errorf("Sign in verbs = %v, want swipes (positive bounds)", submit)
+	}
+	if contains(submit, "typing") {
+		t.Errorf("Sign in should not be typeable, got %v", submit)
+	}
+
+	// The EditText is typeable (and a swipe origin); its label falls back to the
+	// resource-id since it has no text.
+	email := byLabel["EmailField"]
+	if !contains(email, "typing") {
+		t.Errorf("EmailField verbs = %v, want typing", email)
+	}
+	if contains(email, "taps") {
+		t.Errorf("EmailField is not clickable, got %v", email)
+	}
+
+	// The scrollable list yields a scroll candidate.
+	list := byLabel["List"]
+	if !contains(list, "scrolls") {
+		t.Errorf("List verbs = %v, want scrolls", list)
+	}
+
+	// Kinds map verbs to action kinds.
+	for _, candidate := range candidates {
+		if candidate.Verb == "typing" && candidate.Kind != ActionKindInputText {
+			t.Errorf("typing candidate kind = %q, want InputText", candidate.Kind)
+		}
+		if candidate.Verb == "taps" && candidate.Kind != ActionKindTap {
+			t.Errorf("taps candidate kind = %q, want Tap", candidate.Kind)
+		}
+	}
+}
+
+func TestAllCandidatesNilTree(t *testing.T) {
+	v := &Verifier{}
+	if got := v.AllCandidates(); got != nil {
+		t.Errorf("AllCandidates with no tree = %v, want nil", got)
+	}
+}
+
+func TestLLMConfigDetectsMarker(t *testing.T) {
+	v := newLoadedVerifier(t, `globalThis.actions = { kind: "llm", config: { model: "vendor/model" } };`)
+	config, ok := v.LLMConfig()
+	if !ok {
+		t.Fatal("LLMConfig not detected for llm marker")
+	}
+	if config.Model != "vendor/model" {
+		t.Errorf("model = %q, want vendor/model", config.Model)
+	}
+}
+
+func TestLLMConfigAbsentForSeededSpec(t *testing.T) {
+	v := newLoadedVerifier(t, `globalThis.actions = { kind: "builtin", verb: "taps" };`)
+	if _, ok := v.LLMConfig(); ok {
+		t.Error("LLMConfig should be false for a non-llm actions root")
+	}
+}
+
+func TestSampleInputErrorsWithoutBundle(t *testing.T) {
+	v := newLoadedVerifier(t, `globalThis.actions = { kind: "llm", config: { model: "m" } };`)
+	if _, err := v.SampleInput(); err == nil {
+		t.Error("expected SampleInput to error when the sampler is not installed")
+	}
+}
+
+func TestSampleInputDrawsFromCorpus(t *testing.T) {
+	v := newLoadedVerifier(t, `globalThis.__sanderlingSampleInput__ = () => "sampled";`)
+	got, err := v.SampleInput()
+	if err != nil {
+		t.Fatalf("SampleInput: %v", err)
+	}
+	if got != "sampled" {
+		t.Errorf("SampleInput = %q, want sampled", got)
+	}
+}
+
+func newLoadedVerifier(t *testing.T, source string) *Verifier {
+	t.Helper()
+	v, err := New()
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	if err := v.Load(source); err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	return v
+}
+
+func contains(items []string, want string) bool {
+	return slices.Contains(items, want)
+}