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.
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package org.jetbrains.annotations;

import java.lang.annotation.*;


A member or type annotated with TestOnly claims that it should be used from testing code only.


Apart from documentation purposes this annotation is intended to be used by static analysis tools
to validate against element contract violations.


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.

/**
 * A member or type annotated with TestOnly claims that it should be used from testing code only.
 * <p>
 * Apart from documentation purposes this annotation is intended to be used by static analysis tools
 * to validate against element contract violations.
 * <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.
 */
@Documented
@Retention(RetentionPolicy.CLASS)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.FIELD, ElementType.TYPE})
public @interface TestOnly { }