ktesting: install signal handler on demand

The ktesting package is meant to be usable in E2E suites and then must not
affect signal handling in Ginkgo.

test/utils/ktesting/main_test.go

@@ -29,6 +29,10 @@ func TestMain(m *testing.M) {
 	// Bail out early when -help was given as parameter.
 	flag.Parse()
 
+	// The unit tests assume that they run as a unit test, with progress reporting enabled.
+	// This leaks a goroutine, so we have to do it before IgnoreCurrent.
+	initSignals()
+
 	// Must be called *before* creating new goroutines.
 	goleakOpts := []goleak.Option{
 		goleak.IgnoreCurrent(),

test/utils/ktesting/signals.go

@@ -27,7 +27,7 @@ import (
 )
 
 var (
-	interruptCtx context.Context
+	interruptCtx = context.Background()
 
 	defaultProgressReporter = new(progressReporter)
 	defaultSignalChannel    chan os.Signal
@@ -39,10 +39,11 @@ type ginkgoReporter interface {
 	AttachProgressReporter(reporter func() string) func()
 }
 
-func init() {
-	// Setting up signals is intentionally done in an init function because
-	// then importing ktesting in a unit or integration test is sufficient
-	// to activate the signal behavior.
+// initSignals is invoked once when ktesting is used for a `go test` unit test.
+// It implements support for triggering a progress report in
+// a running test when sending it a USR1 signal, similar to the corresponding
+// Ginkgo feature.
+func initSignals() {
 	signalCtx, _ := signal.NotifyContext(context.Background(), os.Interrupt)
 	cancelCtx, cancel := context.WithCancelCause(context.Background())
 	go func() {
@@ -70,6 +71,8 @@ func init() {
 	go defaultProgressReporter.run(interruptCtx, defaultSignalChannel)
 }
 
+var initSignalsOnce sync.Once
+
 type progressReporter struct {
 	mutex           sync.Mutex
 	reporterCounter int64

test/utils/ktesting/tcontext.go

@@ -162,6 +162,15 @@ func Init(tb TB, opts ...InitOption) TContext {
 	tCtx.Cleanup(func() {
 		tCtx.Cancel(cleanupErr(tCtx.Name()).Error())
 	})
+
+	// Only enable signal handling if we are sure that we are not
+	// in a Ginkgo suite. Only structs from the testing package
+	// can implement this interface because it contains an "internal"
+	// method, so this has to run under `go test`.
+	if _, ok := tb.(testing.TB); ok {
+		initSignalsOnce.Do(initSignals)
+	}
+
 	return tCtx
 }