fix(runner): surface focus-tap errors in InputText (#12)

* fix(runner): surface focus-tap errors in InputText action

A failed Tap/TapSelector before InputText was swallowed, so text typed
into the wrong field (or no field) still reported success. Return the
error so the step fails explicitly.

* feat(sample-app): add username EditText and snapshot

Gives the spec a real EditText target (content-desc: username_field)
so the InputText action path can be exercised end-to-end. The typed
value is mirrored into MainActivity.username and surfaced as the
"username" snapshot for spec assertions.

* feat(sample-app): exercise InputText action against username field

Adds typeUsername action and usernameNeverShrinks property to the
sample spec, and extends the integration test to assert the bundled
spec emits an InputText(desc:username_field, "alice") action and that
the property correctly violates when a snapshot reports a shorter
string.

internal/runner/runner.go

@@ -198,9 +198,13 @@ func applyAction(ctx context.Context, drv driver.Driver, action verifier.Action,
 		return drv.Tap(ctx, x, y)
 	case verifier.ActionKindInputText:
 		if x, y, ok := resolveCoordinates(action, tree); ok {
-			_ = drv.Tap(ctx, x, y)
+			if err := drv.Tap(ctx, x, y); err != nil {
+				return err
+			}
 		} else if action.On != "" {
-			_ = drv.TapSelector(ctx, action.On)
+			if err := drv.TapSelector(ctx, action.On); err != nil {
+				return err
+			}
 		}
 		return drv.InputText(ctx, action.Text)
 	default:

internal/runner/runner_test.go

@@ -3,6 +3,7 @@ package runner
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net"
 	"os"
 	"path/filepath"
@@ -234,6 +235,35 @@ func TestRunner_RecordsScreenFieldFromSnapshot(t *testing.T) {
 	}
 }
 
+func TestApplyAction_InputTextSurfacesFocusTapError(t *testing.T) {
+	t.Run("selector focus tap fails", func(t *testing.T) {
+		driverMock := mockdriver.New()
+		driverMock.Failures[mockdriver.ActionTapSelector] = errors.New("adb unreachable")
+		action := verifier.Action{Kind: verifier.ActionKindInputText, On: "id:username", Text: "alice"}
+
+		err := applyAction(context.Background(), driverMock, action, nil)
+		if err == nil {
+			t.Fatalf("expected focus tap failure to surface, got nil")
+		}
+		if containsAction(driverMock.Actions(), mockdriver.ActionInputText, "") {
+			t.Errorf("InputText must not run after focus tap failed: %v", driverMock.Actions())
+		}
+	})
+	t.Run("coordinate focus tap fails", func(t *testing.T) {
+		driverMock := mockdriver.New()
+		driverMock.Failures[mockdriver.ActionTap] = errors.New("tap driver error")
+		action := verifier.Action{Kind: verifier.ActionKindInputText, X: 10, Y: 20, Text: "alice"}
+
+		err := applyAction(context.Background(), driverMock, action, nil)
+		if err == nil {
+			t.Fatalf("expected focus tap failure to surface, got nil")
+		}
+		if containsAction(driverMock.Actions(), mockdriver.ActionInputText, "") {
+			t.Errorf("InputText must not run after focus tap failed: %v", driverMock.Actions())
+		}
+	})
+}
+
 func mustNewVerifier(t *testing.T) *verifier.Verifier {
 	t.Helper()
 	verifierInstance, err := verifier.New()

internal/verifier/spec_integration_test.go

@@ -16,6 +16,8 @@ const sampleAppHierarchyXML = `<?xml version="1.0" encoding="UTF-8"?>
     <node index="0" class="android.widget.LinearLayout" bounds="[64,96][1016,2336]">
       <node index="0" class="android.widget.TextView" text="Clicks: 0" bounds="[100,200][900,300]" />
       <node index="1" class="android.widget.Button" text="Click me" clickable="true" enabled="true" bounds="[400,800][680,920]" />
+      <node index="2" class="android.widget.TextView" text="Username: " bounds="[100,1000][900,1080]" />
+      <node index="3" class="android.widget.EditText" content-desc="username_field" clickable="true" enabled="true" bounds="[100,1200][900,1320]" />
     </node>
   </node>
 </hierarchy>`
@@ -63,18 +65,25 @@ func TestSampleAppSpecTapsClickMe(t *testing.T) {
 	}
 
 	tapHits := 0
-	for range 200 {
+	inputHits := 0
+	for range 400 {
 		action, err := v.NextAction()
 		if err != nil {
 			continue
 		}
-		if action.Kind == ActionKindTap && action.On == "text:Click me" {
+		switch {
+		case action.Kind == ActionKindTap && action.On == "text:Click me":
 			tapHits++
+		case action.Kind == ActionKindInputText && action.On == "desc:username_field" && action.Text == "alice":
+			inputHits++
 		}
 	}
 	if tapHits == 0 {
 		t.Fatal("tapClickMe never fired on sample-app hierarchy")
 	}
+	if inputHits == 0 {
+		t.Fatal("typeUsername never fired on sample-app hierarchy")
+	}
 }
 
 // TestSampleAppSpecPropertiesHold checks the three properties declared in the
@@ -88,31 +97,37 @@ func TestSampleAppSpecPropertiesHold(t *testing.T) {
 	steps := []struct {
 		appState   string
 		clickCount int
+		username   string
 		want       map[string]ltl.Verdict
 	}{
-		{"running", 0, map[string]ltl.Verdict{
+		{"running", 0, "", map[string]ltl.Verdict{
 			"appIsRunning":             ltl.VerdictHolds,
 			"clickCountNonNegative":    ltl.VerdictHolds,
 			"clickCountNeverDecreases": ltl.VerdictHolds,
+			"usernameNeverShrinks":     ltl.VerdictHolds,
 		}},
-		{"running", 5, map[string]ltl.Verdict{
+		{"running", 5, "alice", map[string]ltl.Verdict{
 			"appIsRunning":             ltl.VerdictHolds,
 			"clickCountNonNegative":    ltl.VerdictHolds,
 			"clickCountNeverDecreases": ltl.VerdictHolds,
+			"usernameNeverShrinks":     ltl.VerdictHolds,
 		}},
-		{"running", 3, map[string]ltl.Verdict{
+		{"running", 3, "al", map[string]ltl.Verdict{
 			"appIsRunning":             ltl.VerdictHolds,
 			"clickCountNonNegative":    ltl.VerdictHolds,
 			"clickCountNeverDecreases": ltl.VerdictViolated,
+			"usernameNeverShrinks":     ltl.VerdictViolated,
 		}},
 	}
 
 	for index, step := range steps {
 		stateRaw, _ := json.Marshal(step.appState)
 		countRaw, _ := json.Marshal(step.clickCount)
+		usernameRaw, _ := json.Marshal(step.username)
 		if err := v.PushSnapshot(Snapshots{
 			"app_state":   stateRaw,
 			"click_count": countRaw,
+			"username":    usernameRaw,
 		}, nil); err != nil {
 			t.Fatalf("step %d: %v", index, err)
 		}