https://github.com/JetBrains/java-annotations: A set of annotations used for code inspection support and code documentation. 
/*
 * Copyright 2000-2020 JetBrains s.r.o.
 *
 * 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
 *
 * https://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 org.jetbrains.annotations;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


A member or type annotated with VisibleForTesting claims that its visibility is higher than necessary,
only for testing purposes. In particular:

    
  
  • If public or protected member/type is annotated with VisibleForTesting, 
  it's assumed that package-private access is enough for production code.
    • 
  
  • If package-private member/type is annotated with VisibleForTesting,
  it's assumed that private access is enough for production code.
    • 
  
  • It's illegal to annotate private member/type as VisibleForTesting.
    • 




This annotation means that the annotated element exposes internal data and breaks encapsulation 
of the containing class; the annotation won't prevent its use from production code, developers 
even won't see warnings if their IDE doesn't support the annotation. It's better to provide 
proper API which can be used in production as well as in tests.

Since:20.0.0
/**
 * A member or type annotated with VisibleForTesting claims that its visibility is higher than necessary,
 * only for testing purposes. In particular:
 * <ul>
 *   <li>If public or protected member/type is annotated with VisibleForTesting, 
 *   it's assumed that package-private access is enough for production code.</li>
 *   <li>If package-private member/type is annotated with VisibleForTesting,
 *   it's assumed that private access is enough for production code.</li>
 *   <li>It's illegal to annotate private member/type as VisibleForTesting.</li>
 * </ul>
 * <p>
 * This annotation means that the annotated element exposes internal data and breaks encapsulation 
 * of the containing class; the annotation won't prevent its use from production code, developers 
 * even won't see warnings if their IDE doesn't support the annotation. It's better to provide 
 * proper API which can be used in production as well as in tests.
 * 
 * @since 20.0.0
 */
@Documented
@Retention(RetentionPolicy.CLASS)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.FIELD, ElementType.TYPE})
public @interface VisibleForTesting { }