Add unit tests for internal/validator Validate error paths

Cover the driver-list failure, an invalid nodeSelector on a listed driver,
and the node-list failure, using fake-client interceptors. internal/validator
reaches 100% statement coverage.

Signed-off-by: Abrar Shivani <ashivani@nvidia.com>

Author: abrarshivani

internal/validator/validator_errors_test.go

@@ -0,0 +1,103 @@
+/**
+# Copyright (c) NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package validator
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/client/fake"
+	"sigs.k8s.io/controller-runtime/pkg/client/interceptor"
+
+	nvidiav1alpha1 "github.com/NVIDIA/gpu-operator/api/nvidia/v1alpha1"
+)
+
+func newValidatorScheme(t *testing.T) *runtime.Scheme {
+	t.Helper()
+	s := runtime.NewScheme()
+	require.NoError(t, nvidiav1alpha1.AddToScheme(s))
+	require.NoError(t, corev1.AddToScheme(s))
+	return s
+}
+
+func TestValidateReturnsErrorWhenDriverListFails(t *testing.T) {
+	s := newValidatorScheme(t)
+
+	requested := makeTestDriver("requested", nil, false)
+	c := fake.NewClientBuilder().
+		WithScheme(s).
+		WithInterceptorFuncs(interceptor.Funcs{
+			List: func(ctx context.Context, cl client.WithWatch, list client.ObjectList, opts ...client.ListOption) error {
+				if _, ok := list.(*nvidiav1alpha1.NVIDIADriverList); ok {
+					return errors.New("driver list boom")
+				}
+				return cl.List(ctx, list, opts...)
+			},
+		}).
+		Build()
+	nsv := NewNodeSelectorValidator(c)
+
+	err := nsv.Validate(context.Background(), requested)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "driver list boom")
+}
+
+func TestValidateReturnsErrorWhenListedDriverHasInvalidSelector(t *testing.T) {
+	s := newValidatorScheme(t)
+
+	requested := makeTestDriver("requested", nil, false)
+	invalid := makeTestDriver("invalid-default", map[string]string{"nodepool": "b"}, true)
+
+	c := fake.NewClientBuilder().
+		WithScheme(s).
+		WithObjects(invalid).
+		Build()
+	nsv := NewNodeSelectorValidator(c)
+
+	err := nsv.Validate(context.Background(), requested)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "default NVIDIADriver")
+	require.Contains(t, err.Error(), "cannot use nodeSelector")
+}
+
+func TestValidateReturnsErrorWhenNodeListFails(t *testing.T) {
+	s := newValidatorScheme(t)
+
+	requested := makeTestDriver("requested", map[string]string{"nodepool": "a"}, false)
+	c := fake.NewClientBuilder().
+		WithScheme(s).
+		WithObjects(requested).
+		WithInterceptorFuncs(interceptor.Funcs{
+			List: func(ctx context.Context, cl client.WithWatch, list client.ObjectList, opts ...client.ListOption) error {
+				if _, ok := list.(*corev1.NodeList); ok {
+					return errors.New("node list boom")
+				}
+				return cl.List(ctx, list, opts...)
+			},
+		}).
+		Build()
+	nsv := NewNodeSelectorValidator(c)
+
+	err := nsv.Validate(context.Background(), requested)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "node list boom")
+}