fix(ios): three unbacked reads report not-supported instead of success

RecentLogs returned an empty slice, Metrics a zeroed sample and Health a
hardcoded Ready: true, which are the same values a working read returns. Every
property over state.logs held vacuously on iOS with nothing saying the logs were
never read. driver.ErrNotSupported makes the silence representable.

internal/driver/ioscompanion/driver.go

@@ -1107,21 +1107,24 @@ func (d *Driver) WaitForIdle(ctx context.Context, _ time.Duration) error {
 	return nil
 }
 
-// RecentLogs returns no entries: the companion log RPC is a follow-up, so v1
-// reports an empty slice rather than failing. Every property reading state.logs
-// therefore holds vacuously on iOS and nothing says so; closing it means
-// tailing idb's streaming log RPC and mapping os_log levels onto the
-// single-letter scale driver.LogEntry declares.
+// RecentLogs, Metrics and Health have no companion RPC behind them yet, so
+// each reports driver.ErrNotSupported. An empty log slice, a zeroed sample and
+// a hardcoded Ready are the same values a working read can return, so answering
+// with them told the runner three checks had passed that never ran and left
+// every property reading state.logs holding vacuously with nothing saying so.
+// Closing them means tailing the streaming log RPC and mapping os_log levels
+// onto the single-letter scale driver.LogEntry declares, sampling the app
+// process, and probing the bridge for readiness.
 func (d *Driver) RecentLogs(_ context.Context, _ time.Time, _ string) ([]driver.LogEntry, error) {
-	return []driver.LogEntry{}, nil
+	return nil, driver.ErrNotSupported
 }
 
 func (d *Driver) Metrics(_ context.Context, _ string) (driver.Metrics, error) {
-	return driver.Metrics{}, nil
+	return driver.Metrics{}, driver.ErrNotSupported
 }
 
 func (d *Driver) Health(_ context.Context) (driver.Health, error) {
-	return driver.Health{Ready: true, Platform: "ios"}, nil
+	return driver.Health{}, driver.ErrNotSupported
 }
 
 // ForegroundApp reports the foreground app. It returns the app under test when

internal/driver/ioscompanion/driver_test.go

@@ -699,14 +699,35 @@ func TestForegroundAppFallsBackToOtherRunningUserApp(t *testing.T) {
 	}
 }
 
-func TestHealthReportsIOS(t *testing.T) {
+// The three reads the companion has no RPC for must say so. Answering an empty
+// log slice, a zeroed sample or Ready reports three checks as having passed
+// that never ran, and a spec's log properties then hold on evidence nobody
+// collected.
+func TestUnbackedReadsReportNotSupported(t *testing.T) {
 	d := newTestDriver(&fakeCompanion{})
-	health, err := d.Health(context.Background())
-	if err != nil {
-		t.Fatalf("Health: %v", err)
+
+	logs, err := d.RecentLogs(context.Background(), time.Time{}, "E")
+	if !errors.Is(err, driver.ErrNotSupported) {
+		t.Errorf("RecentLogs err = %v, want driver.ErrNotSupported", err)
 	}
-	if !health.Ready || health.Platform != "ios" {
-		t.Fatalf("Health = %+v, want ready ios", health)
+	if len(logs) != 0 {
+		t.Errorf("RecentLogs returned %d entries alongside its error", len(logs))
+	}
+
+	metrics, err := d.Metrics(context.Background(), "com.fixture")
+	if !errors.Is(err, driver.ErrNotSupported) {
+		t.Errorf("Metrics err = %v, want driver.ErrNotSupported", err)
+	}
+	if metrics != (driver.Metrics{}) {
+		t.Errorf("Metrics = %+v, want the zero sample", metrics)
+	}
+
+	health, err := d.Health(context.Background())
+	if !errors.Is(err, driver.ErrNotSupported) {
+		t.Errorf("Health err = %v, want driver.ErrNotSupported", err)
+	}
+	if health.Ready {
+		t.Errorf("Health = %+v: the driver reports a readiness check it never ran", health)
 	}
 }