Add omitted test for mock validator

pkg/storage/mock/validator/validator.go

 // Copyright 2020 The Swarm Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
+
 package validator
 
 import (

pkg/storage/mock/validator/validator_test.go

+// Copyright 2020 The Swarm Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package validator_test
+
+import (
+	"testing"
+
+	"github.com/ethersphere/bee/pkg/storage/mock/validator"
+	"github.com/ethersphere/bee/pkg/swarm"
+)
+
+func TestMockValidator(t *testing.T) {
+	validAddr := swarm.NewAddress([]byte("foo"))
+	invalidAddr := swarm.NewAddress([]byte("bar"))
+
+	validContent := []byte("xyzzy")
+	invalidContent := []byte("yzzyx")
+
+	validator := validator.NewMockValidator(validAddr, validContent)
+
+	ch := swarm.NewChunk(validAddr, validContent)
+	if !validator.Validate(ch) {
+		t.Fatalf("chunk '%v' should be valid", ch)
+	}
+
+	ch = swarm.NewChunk(invalidAddr, validContent)
+	if validator.Validate(ch) {
+		t.Fatalf("chunk '%v' should be invalid", ch)
+	}
+
+	ch = swarm.NewChunk(validAddr, invalidContent)
+	if validator.Validate(ch) {
+		t.Fatalf("chunk '%v' should be invalid", ch)
+	}
+
+	ch = swarm.NewChunk(invalidAddr, invalidContent)
+	if validator.Validate(ch) {
+		t.Fatalf("chunk '%v' should be invalid", ch)
+	}
+}