test(chrome): one launch preamble, and parity now pins ground truth

48 of 51 call sites shared one eight-line block that opened a fixture server,
launched chrome and checked the error. The three left are the launch tests
themselves, where what the helper hardcodes is the subject.

The audit called four tests superseded by fact_parity_test.go. They were not:
parity asserts the two producers agree and that each fact appears both ways,
never that either reading is right, so deleting them would have removed the only
thing anchoring the pair to reality. The values they pinned are now asserted
inside parity against both producers, and the shadow fixture has ground truth
where it had none.

internal/driver/chrome/element_state_test.go

@@ -5,12 +5,9 @@ package chrome
 import (
 	"context"
 	"encoding/json"
-	"net/http"
-	"net/http/httptest"
 	"path/filepath"
 	"slices"
 	"testing"
-	"time"
 
 	"github.com/chromedp/chromedp"
 
@@ -31,16 +28,7 @@ import (
 // reading element.getAttribute("checked") reports the starting value forever and
 // passes any test that only reads a freshly loaded page.
 func TestElementState_ChecksTrackTheLiveDOM(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/element-state.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
+	d, ctx := launchChrome(t, testdataServer(t).URL+"/element-state.html")
 	installStateProbe(ctx, t, d)
 
 	requireChecked(ctx, t, d, "toggle-all", false)
@@ -96,16 +84,7 @@ func requireChecked(
 // the same reason `checked` is: the attribute records only where the page
 // started.
 func TestElementState_ReportsTheOtherDocumentedBooleans(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/element-state.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
+	d, ctx := launchChrome(t, testdataServer(t).URL+"/element-state.html")
 	installStateProbe(ctx, t, d)
 
 	requireBoolean(
@@ -191,43 +170,6 @@ func TestElementState_ReportsTheOtherDocumentedBooleans(t *testing.T) {
 	)
 }
 
-// Every editable field states `secure`, false included. internal/verifier
-// redacts a typed value whenever the target does not positively report "not a
-// secure entry", so a dump that omitted the key on an ordinary text field would
-// redact the whole recent-action memory on web.
-func TestElementState_SecureStatesEveryEditableField(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/element-state.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
-
-	for _, testCase := range []struct {
-		selector string
-		want     bool
-	}{
-		{"id:secret", true},
-		{"id:editing", false},
-	} {
-		element := elementInHierarchyDump(ctx, t, d, testCase.selector)
-		if !element.SecureReported() {
-			t.Errorf("the dump states no secure fact for %s", testCase.selector)
-		}
-		if element.Secure != testCase.want {
-			t.Errorf("%s secure = %v, want %v", testCase.selector, element.Secure, testCase.want)
-		}
-	}
-
-	if button := elementInHierarchyDump(ctx, t, d, "id:save"); button.SecureReported() {
-		t.Error("a button is not a text entry and states nothing")
-	}
-}
-
 // Focus belongs to the node the user is typing into, not to the element the
 // shadow tree is mounted on.
 //
@@ -237,16 +179,7 @@ func TestElementState_SecureStatesEveryEditableField(t *testing.T) {
 // to type when the field it tapped is not the one holding focus, so every
 // InputText step on such an app failed and the run aborted.
 func TestElementState_FocusDescendsIntoTheShadowRoot(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/shadow-focus.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
+	d, ctx := launchChrome(t, testdataServer(t).URL+"/shadow-focus.html")
 
 	field := elementInHierarchyDump(ctx, t, d, "id:shadow-field")
 	x, y := field.Bounds.Center()
@@ -274,16 +207,7 @@ func TestElementState_FocusDescendsIntoTheShadowRoot(t *testing.T) {
 // Both fields are tapped, because reporting the first editable in the tree
 // would satisfy the email half of this and still type into the wrong field.
 func TestElementState_FocusFollowsTheCaretToItsField(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/compose-backing-input.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
+	d, ctx := launchChrome(t, testdataServer(t).URL+"/compose-backing-input.html")
 
 	for _, field := range []string{"EmailField", "PasswordField"} {
 		tapped := elementInHierarchyDump(ctx, t, d, "id:"+field)
@@ -466,16 +390,7 @@ func installStateProbe(ctx context.Context, t *testing.T, d *Driver) {
 // green having actuated nothing. The page records its own keydown events, so
 // what is asserted here is what the DOM received, not what the driver sent.
 func TestPressKey_ArrivesAtThePage(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/element-state.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
+	d, ctx := launchChrome(t, testdataServer(t).URL+"/element-state.html")
 
 	for _, keyCase := range []struct{ key, want string }{
 		{"enter", "Enter"},
@@ -544,16 +459,7 @@ func keysSeenByThePage(ctx context.Context, t *testing.T, d *Driver) []string {
 // pkg/spec/src/web-runtime.ts already answers `state.selected === true`, so the
 // two hosts also disagreed about the same fact on the same page.
 func TestElementState_AComponentPropertyDoesNotBlankTheTree(t *testing.T) {
-	server := httptest.NewServer(http.FileServer(http.Dir("testdata")))
-	defer server.Close()
-
-	d := New()
-	defer d.Terminate(context.Background())
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-	defer cancel()
-	if err := d.Launch(ctx, server.URL+"/custom-element-flags.html", false, nil); err != nil {
-		t.Fatalf("Launch: %v", err)
-	}
+	d, ctx := launchChrome(t, testdataServer(t).URL+"/custom-element-flags.html")
 
 	dump, err := d.Hierarchy(ctx)
 	if err != nil {