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Functional Tests for Tools4j Config
There is a newer version: 0.15.0
package org.deephacks.tools4j.config.test;

import java.lang.reflect.Field;
import java.util.Collection;

import org.deephacks.tools4j.config.model.Lookup;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

/**
 * MockLookup is responsible for mocking lookups.
 */
public class MockLookup extends Lookup {
    private Multimap, Object> instances = ArrayListMultimap.create();

    @Override
    public  T lookup(Class clazz) {
        @SuppressWarnings("unchecked")
        Collection result = (Collection) instances.get(clazz);
        if (result.size() != 0) {
            return result.iterator().next();
        }
        return super.lookup(clazz);
    }

    @SuppressWarnings("unchecked")
    @Override
    public  Collection lookupAll(Class clazz) {
        Collection result = (Collection) instances.get(clazz);
        if (result.size() != 0) {
            return result;
        }
        return super.lookupAll(clazz);
    }

    public static void setMockInstances(Class clazz, Object... instances) {
        overrideDefault();
        MockLookup thisMockLookup = (MockLookup) Lookup.get();
        thisMockLookup.instances.clear();
        for (Object object : instances) {
            thisMockLookup.instances.put(clazz, object);
        }
    }

    public static void addMockInstances(Class clazz, Object... instances) {
        overrideDefault();
        MockLookup thisMockLookup = (MockLookup) Lookup.get();
        for (Object object : instances) {
            thisMockLookup.instances.put(clazz, object);
        }
    }

    private static void overrideDefault() throws ExceptionInInitializerError {
        try {
            System.setProperty(Lookup.class.getName(), MockLookup.class.getName());
            if (Lookup.get().getClass() != MockLookup.class) {
                // Someone else initialized lookup first. Try to force our way.
                Field defaultLookup = Lookup.class.getDeclaredField("LOOKUP");
                defaultLookup.setAccessible(true);
                defaultLookup.set(null, null);
            }

            if (!Lookup.get().getClass().equals(MockLookup.class))
                throw new RuntimeException("Could not set MockLookup");
        } catch (Exception x) {
            throw new ExceptionInInitializerError(x);
        }
    }

    public static void resetToDefault() throws ExceptionInInitializerError {
        try {
            System.setProperty(Lookup.class.getName(), "");
            Field defaultLookup = Lookup.class.getDeclaredField("LOOKUP");
            defaultLookup.setAccessible(true);
            defaultLookup.set(null, null);
            if (!Lookup.get().getClass().equals(Lookup.class))
                throw new RuntimeException("Could reset to default lookup");

        } catch (Exception x) {
            throw new ExceptionInInitializerError(x);
        }
    }

}