ktesting: add namespace support

Many helper packages need to know the test namespace in addition to the client.
Supporting passing of that information through the TContext avoids adding
another parameter to such helper packages.

This mirrors similar functionality in framework.Framework which also provides
a namespace to the test and packages taking such a parameter.

test/utils/ktesting/tcontext.go

@@ -392,6 +392,9 @@ type TC struct {
 	dynamic       dynamic.Interface
 	apiextensions apiextensions.Interface
 
+	// for WithNamespace
+	namespace string
+
 	// capture, if non-nil, changes Error/Errorf/Fatal/Fatalf/Fail/FailNow so
 	// that they intercept the problem and convert to errors. Log messages
 	// are passed through.
@@ -598,3 +601,20 @@ func (tc *TC) Require(actual interface{}, extra ...interface{}) gomega.Assertion
 func (tc *TC) Assert(actual interface{}, extra ...interface{}) gomega.Assertion {
 	return gomegaAssertion(tc, false, actual, extra...)
 }
+
+// WithNamespace creates a new context with a Kubernetes namespace name for retrieval through [Namespace].
+func (tc *TC) WithNamespace(namespace string) TContext {
+	tc = tc.clone()
+	tc.namespace = namespace
+	return tc
+}
+
+// Namespace returns the Kubernetes namespace name that was set previously
+// through WithNamespace and the empty string if none is available.
+//
+// This namespace is the one to be used by tests which need to create namespace-scoped
+// objects. The name is guaranteed to be unique for the test context, so tests running
+// in parallel need to be set up so that each test has its own namespace.
+func (tc *TC) Namespace() string {
+	return tc.namespace
+}

test/utils/ktesting/tcontext_test.go

@@ -20,6 +20,7 @@ import (
 	"sync"
 	"testing"
 
+	"github.com/onsi/gomega"
 	"github.com/stretchr/testify/assert"
 
 	apiextensions "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset"
@@ -128,3 +129,10 @@ func TestRun(t *testing.T) {
 		t.Errorf("parent TContext should not have been cancelled: %v", err)
 	}
 }
+
+func TestWithNamespace(t *testing.T) {
+	tCtx := ktesting.Init(t)
+	namespace := "foo"
+	tCtxWithNamespace := tCtx.WithNamespace(namespace)
+	tCtx.Expect(tCtxWithNamespace.Namespace()).To(gomega.Equal(namespace))
+}