base/test/android/javatests/src/org/chromium/base/test/util/JniMocker.java

// Copyright 2018 The Chromium 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 org.chromium.base.test.util;

import org.junit.rules.ExternalResource;

import org.chromium.base.JniStaticTestMocker;
import org.chromium.base.annotations.NativeMethods;

import java.util.ArrayList;

/**
 * A test rule to set up and tear down native implementation mocks.
 */
public class JniMocker extends ExternalResource {
    private final ArrayList<JniStaticTestMocker> mHooks = new ArrayList<>();

    /**
     * Sets the native implementation of the class using a JniStaticTestMocker
     *
     * All TEST_HOOKS set with this function will have their test instance
     * set to null after each test is run.
     *
     * @param T    Interface type that implements {@link NativeMethods}
     * @param hook Instance of the corresponding JniStaticTestMocker in the
     *             wrapper class generated by the JNI annotation processor
     * @param testInst Mock instance of type T which will be set as the
     *                 native implementation to be used in tests.
     */
    public <T> void mock(JniStaticTestMocker<T> hook, T testInst) {
        hook.setInstanceForTesting(testInst);
        mHooks.add(hook);
    }

    @Override
    @SuppressWarnings("unchecked")
    protected void after() {
        for (JniStaticTestMocker hook : mHooks) {
            hook.setInstanceForTesting(null);
        }
        mHooks.clear();
    }
}