DefaultEvictor: introduce no-eviction policy

NoEvictionPolicy dictates whether a no-eviction policy is prefered or mandatory.
Needs to be used with caution as this will give users ability to protect their pods
from eviction. Which might work against enfored policies. E.g. plugins evicting pods
violating security policies.

pkg/framework/plugins/defaultevictor/validation_test.go

@@ -0,0 +1,64 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+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 defaultevictor
+
+import (
+	"fmt"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	utilptr "k8s.io/utils/ptr"
+	"sigs.k8s.io/descheduler/pkg/api"
+)
+
+func TestValidateDefaultEvictorArgs(t *testing.T) {
+	tests := []struct {
+		name    string
+		args    *DefaultEvictorArgs
+		errInfo error
+	}{
+		{
+			name: "passing invalid priority",
+			args: &DefaultEvictorArgs{
+				PriorityThreshold: &api.PriorityThreshold{
+					Value: utilptr.To[int32](1),
+					Name:  "priority-name",
+				},
+			},
+			errInfo: fmt.Errorf("priority threshold misconfigured, only one of priorityThreshold fields can be set"),
+		}, {
+			name: "passing invalid no eviction policy",
+			args: &DefaultEvictorArgs{
+				NoEvictionPolicy: "invalid-no-eviction-policy",
+			},
+			errInfo: fmt.Errorf("noEvictionPolicy accepts only %q values", []NoEvictionPolicy{PreferredNoEvictionPolicy, MandatoryNoEvictionPolicy}),
+		},
+	}
+
+	for _, testCase := range tests {
+		t.Run(testCase.name, func(t *testing.T) {
+			validateErr := ValidateDefaultEvictorArgs(runtime.Object(testCase.args))
+			if validateErr == nil || testCase.errInfo == nil {
+				if validateErr != testCase.errInfo {
+					t.Errorf("expected validity of plugin config: %q but got %q instead", testCase.errInfo, validateErr)
+				}
+			} else if validateErr.Error() != testCase.errInfo.Error() {
+				t.Errorf("expected validity of plugin config: %q but got %q instead", testCase.errInfo, validateErr)
+			}
+		})
+	}
+}