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Testing Fallback Method Resolution Implementation in Netflix Hystrix

This test suite validates the fallback method functionality in Netflix’s Hystrix library, specifically focusing on method parameter matching and inheritance scenarios in the JavaNica contribution. The tests ensure proper fallback method resolution with various parameter configurations and extended class hierarchies.

Test Coverage Overview

The test suite provides comprehensive coverage of fallback method resolution scenarios in Hystrix commands.

Tests extended fallback method parameter matching
Validates fallback resolution in inheritance hierarchies
Covers both standard and extended command configurations
Tests null fallback scenarios and parameter type validation

Implementation Analysis

The testing approach uses JUnit with DataProviderRunner for parameterized testing of fallback method scenarios.

Key patterns include:

Method reflection for dynamic method resolution testing
Inheritance-based test structures using Common and Service classes
Parameter type assertion validation
Boolean flag testing for extended parameter handling

Technical Details

Testing infrastructure includes:

JUnit test framework with DataProviderRunner extension
HystrixCommand annotations for method configuration
MethodProvider utility for fallback resolution
Reflection-based method parameter validation

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Systematic validation of parameter type matching
Clear test method naming conventions
Proper test setup and assertion organization
Comprehensive edge case coverage for inheritance scenarios
Effective use of test data providers for parameterized testing

netflix/hystrix

hystrix-contrib/hystrix-javanica/src/test/java/com/netflix/hystrix/contrib/javanica/util/FallbackMethodTest.java

            
/**
 * Copyright 2016 Netflix, Inc.
 *
 * 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
 *
 *     http://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 com.netflix.hystrix.contrib.javanica.util;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.utils.MethodProvider;
import com.tngtech.java.junit.dataprovider.DataProvider;
import com.tngtech.java.junit.dataprovider.DataProviderRunner;
import org.junit.Test;
import org.junit.runner.RunWith;

import java.lang.reflect.Method;

import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNull;

/**
 * Created by dmgcodevil.
 */
@RunWith(DataProviderRunner.class)
public class FallbackMethodTest {

    @Test
    public void testGetExtendedFallback() throws NoSuchMethodException {
        // given
        Method command = Service.class.getDeclaredMethod("command", String.class, Integer.class);
        // when
        Method extFallback = MethodProvider.getInstance().getFallbackMethod(Service.class, command).getMethod();
        // then
        assertParamsTypes(extFallback, String.class, Integer.class, Throwable.class);
    }

    @Test
    @DataProvider({"true", "false"})
    public void testGetFallbackForExtendedCommand(boolean extended) throws NoSuchMethodException {
        // given
        Method extFallback = Service.class.getDeclaredMethod("extCommand", String.class, Integer.class, Throwable.class);
        // when
        Method fallback = MethodProvider.getInstance().getFallbackMethod(Service.class, extFallback, extended).getMethod();
        // then
        assertParamsTypes(fallback, String.class, Integer.class, Throwable.class);
    }

    public void testGetFallbackForExtendedCommandV2() throws NoSuchMethodException {
        // given
        Method extFallback = Service.class.getDeclaredMethod("extCommandV2", String.class, Integer.class, Throwable.class);
        // when
        Method fallback = MethodProvider.getInstance().getFallbackMethod(Service.class, extFallback, true).getMethod();
        // then
        assertParamsTypes(fallback, String.class, Integer.class);
    }

    public void testGetFallbackForExtendedCommandV2_extendedParameterFalse() throws NoSuchMethodException {
        // given
        Method extFallback = Service.class.getDeclaredMethod("extCommandV2", String.class, Integer.class, Throwable.class);
        // when
        Method fallback = MethodProvider.getInstance().getFallbackMethod(Service.class, extFallback, false).getMethod();
        // then
        assertNull(fallback);
    }


    private static void assertParamsTypes(Method method, Class<?>... expected) {
        assertEquals(expected.length, method.getParameterTypes().length);
        Class<?>[] actual = method.getParameterTypes();
        assertArrayEquals(expected, actual);
    }

    private static class Common {
        private String fallback(String s, Integer i) {
            return null;
        }

        private String fallbackV2(String s, Integer i) {
            return null;
        }
    }

    private static class Service extends Common{

        @HystrixCommand(fallbackMethod = "fallback")
        public String command(String s, Integer i) {
            return null;
        }

        @HystrixCommand(fallbackMethod = "fallback")
        public String extCommand(String s, Integer i, Throwable throwable) {
            return null;
        }


        @HystrixCommand(fallbackMethod = "fallbackV2")
        public String extCommandV2(String s, Integer i, Throwable throwable) {
            return null;
        }


        public String fallback(String s, Integer i, Throwable throwable) {
            return null;
        }

    }

}