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Testing Interface Serialization Implementation in Google GSON

This test suite validates GSON’s capabilities for handling Java interfaces in serialization scenarios. It verifies proper JSON conversion of objects implementing interfaces and interface-based field serialization.

Test Coverage Overview

The test suite provides comprehensive coverage of interface-based serialization scenarios in GSON:

Interface implementation serialization
Object fields implementing interfaces
JSON string validation and formatting
Object wrapper handling with interface fields

Implementation Analysis

The testing approach utilizes JUnit framework with Truth assertions to validate GSON’s interface handling. The implementation follows a clear pattern of setting up test objects, performing serialization, and verifying JSON output against expected strings.

Key patterns include:

Test object initialization in @Before setup
Interface implementation verification
Nested object serialization testing

Technical Details

Testing infrastructure includes:

JUnit 4 testing framework
Google Truth assertion library
GSON serialization library
Custom test interfaces and implementing classes
Object wrapper patterns for nested testing

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Clear test method naming conventions
Proper test setup and initialization
Isolated test cases for specific functionality
Consistent assertion patterns
Well-structured test helper classes

google/gson

gson/src/test/java/com/google/gson/functional/InterfaceTest.java

            
/*
 * Copyright (C) 2008 Google 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.google.gson.functional;

import static com.google.common.truth.Truth.assertThat;

import com.google.gson.Gson;
import org.junit.Before;
import org.junit.Test;

/**
 * Functional tests involving interfaces.
 *
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
public class InterfaceTest {
  private static final String OBJ_JSON = "{\"someStringValue\":\"StringValue\"}";

  private Gson gson;
  private TestObject obj;

  @Before
  public void setUp() throws Exception {
    gson = new Gson();
    obj = new TestObject("StringValue");
  }

  @Test
  public void testSerializingObjectImplementingInterface() {
    assertThat(gson.toJson(obj)).isEqualTo(OBJ_JSON);
  }

  @Test
  public void testSerializingInterfaceObjectField() {
    TestObjectWrapper objWrapper = new TestObjectWrapper(obj);
    assertThat(gson.toJson(objWrapper)).isEqualTo("{\"obj\":" + OBJ_JSON + "}");
  }

  private static interface TestObjectInterface {
    // Holder
  }

  private static class TestObject implements TestObjectInterface {
    @SuppressWarnings("unused")
    private String someStringValue;

    private TestObject(String value) {
      this.someStringValue = value;
    }
  }

  private static class TestObjectWrapper {
    @SuppressWarnings("unused")
    private TestObjectInterface obj;

    private TestObjectWrapper(TestObjectInterface obj) {
      this.obj = obj;
    }
  }
}