Add discriminated union serialization tests

src/test/java/com/stripe/net/DiscriminatedUnionSerializationTest.java

@@ -0,0 +1,351 @@
+package com.stripe.net;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.google.gson.FieldNamingPolicy;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import com.stripe.model.StripeObject;
+import java.io.IOException;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+public class DiscriminatedUnionSerializationTest {
+  private final ApiRequestParamsConverter converter = new ApiRequestParamsConverter();
+
+  private final Gson testGson =
+      new GsonBuilder()
+          .registerTypeAdapterFactory(new TestColorTypeAdapterFactory())
+          .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
+          .create();
+
+  // ---------------------------------------------------------------------------
+  // Request-side fixtures — standalone union
+  // The parent params hold an Object-typed field that can hold any variant.
+  // ---------------------------------------------------------------------------
+
+  @SuppressWarnings("UnusedVariable")
+  private static class TestCreateParams extends ApiRequestParams {
+    @SerializedName("color")
+    Object color;
+
+    @SerializedName("name")
+    String name;
+  }
+
+  @SuppressWarnings("UnusedVariable")
+  private static class TestRgbColorParams extends ApiRequestParams {
+    @SerializedName("model")
+    String model = "rgb";
+
+    @SerializedName("r")
+    Long r;
+
+    @SerializedName("g")
+    Long g;
+
+    @SerializedName("b")
+    Long b;
+  }
+
+  @SuppressWarnings("UnusedVariable")
+  private static class TestHsvColorParams extends ApiRequestParams {
+    @SerializedName("model")
+    String model = "hsv";
+
+    @SerializedName("h")
+    Long h;
+
+    @SerializedName("s")
+    Long s;
+
+    @SerializedName("v")
+    Long v;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Request-side fixtures — inline union
+  // The parent params hold the discriminator and each variant's fields directly.
+  // ---------------------------------------------------------------------------
+
+  @SuppressWarnings("UnusedVariable")
+  private static class TestInlineParams extends ApiRequestParams {
+    @SerializedName("type")
+    String type;
+
+    @SerializedName("card")
+    TestCardParams card;
+
+    @SerializedName("bank")
+    TestBankParams bank;
+  }
+
+  @SuppressWarnings("UnusedVariable")
+  private static class TestCardParams extends ApiRequestParams {
+    @SerializedName("number")
+    String number;
+
+    @SerializedName("exp_month")
+    Long expMonth;
+  }
+
+  @SuppressWarnings("UnusedVariable")
+  private static class TestBankParams extends ApiRequestParams {
+    @SerializedName("routing_number")
+    String routingNumber;
+
+    @SerializedName("account_number")
+    String accountNumber;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Response-side fixtures
+  // ---------------------------------------------------------------------------
+
+  private static class TestColorEntity extends StripeObject {
+    @SerializedName("model")
+    String model;
+  }
+
+  private static class TestRgbColorEntity extends TestColorEntity {
+    @SerializedName("r")
+    Long r;
+
+    @SerializedName("g")
+    Long g;
+
+    @SerializedName("b")
+    Long b;
+  }
+
+  private static class TestHsvColorEntity extends TestColorEntity {
+    @SerializedName("h")
+    Long h;
+
+    @SerializedName("s")
+    Long s;
+
+    @SerializedName("v")
+    Long v;
+  }
+
+  private static class TestColorTypeAdapterFactory implements TypeAdapterFactory {
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+      if (!TestColorEntity.class.isAssignableFrom(type.getRawType())) {
+        return null;
+      }
+      return (TypeAdapter<T>)
+          new TypeAdapter<TestColorEntity>() {
+            @Override
+            @SuppressWarnings("unchecked")
+            public void write(JsonWriter out, TestColorEntity value) throws IOException {
+              ((TypeAdapter<TestColorEntity>) gson.getAdapter(value.getClass())).write(out, value);
+            }
+
+            @Override
+            public TestColorEntity read(JsonReader in) throws IOException {
+              JsonObject obj = JsonParser.parseReader(in).getAsJsonObject();
+              String model = obj.has("model") ? obj.get("model").getAsString() : null;
+              if ("rgb".equals(model)) {
+                return gson.getDelegateAdapter(
+                        TestColorTypeAdapterFactory.this, TypeToken.get(TestRgbColorEntity.class))
+                    .fromJsonTree(obj);
+              } else if ("hsv".equals(model)) {
+                return gson.getDelegateAdapter(
+                        TestColorTypeAdapterFactory.this, TypeToken.get(TestHsvColorEntity.class))
+                    .fromJsonTree(obj);
+              }
+              return gson.getDelegateAdapter(
+                      TestColorTypeAdapterFactory.this, TypeToken.get(TestColorEntity.class))
+                  .fromJsonTree(obj);
+            }
+          };
+    }
+  }
+
+  private static class TestColorContainer extends StripeObject {
+    @SerializedName("color")
+    TestColorEntity color;
+
+    @SerializedName("name")
+    String name;
+  }
+
+  private static class TestPaymentEntity extends StripeObject {
+    @SerializedName("type")
+    String type;
+
+    @SerializedName("card")
+    TestCardEntity card;
+
+    @SerializedName("bank")
+    TestBankEntity bank;
+  }
+
+  private static class TestCardEntity extends StripeObject {
+    @SerializedName("number")
+    String number;
+
+    @SerializedName("exp_month")
+    Long expMonth;
+  }
+
+  private static class TestBankEntity extends StripeObject {
+    @SerializedName("routing_number")
+    String routingNumber;
+
+    @SerializedName("account_number")
+    String accountNumber;
+  }
+
+  // ---------------------------------------------------------------------------
+  // Tests — request side (params → map)
+  // ---------------------------------------------------------------------------
+
+  @Test
+  @SuppressWarnings("unchecked")
+  public void testStandaloneUnion_RgbVariant_Serialization() {
+    TestRgbColorParams rgb = new TestRgbColorParams();
+    rgb.r = 255L;
+    rgb.g = 128L;
+    rgb.b = 0L;
+
+    TestCreateParams params = new TestCreateParams();
+    params.color = rgb;
+    params.name = "sunset";
+
+    Map<String, Object> map = converter.convert(params);
+    assertEquals("sunset", map.get("name"));
+
+    Map<String, Object> colorMap = (Map<String, Object>) map.get("color");
+    assertEquals("rgb", colorMap.get("model"));
+    assertEquals(255L, colorMap.get("r"));
+    assertEquals(128L, colorMap.get("g"));
+    assertEquals(0L, colorMap.get("b"));
+  }
+
+  @Test
+  @SuppressWarnings("unchecked")
+  public void testStandaloneUnion_HsvVariant_Serialization() {
+    TestHsvColorParams hsv = new TestHsvColorParams();
+    hsv.h = 30L;
+    hsv.s = 100L;
+    hsv.v = 100L;
+
+    TestCreateParams params = new TestCreateParams();
+    params.color = hsv;
+    params.name = "orange";
+
+    Map<String, Object> map = converter.convert(params);
+    assertEquals("orange", map.get("name"));
+
+    Map<String, Object> colorMap = (Map<String, Object>) map.get("color");
+    assertEquals("hsv", colorMap.get("model"));
+    assertEquals(30L, colorMap.get("h"));
+    assertEquals(100L, colorMap.get("s"));
+    assertEquals(100L, colorMap.get("v"));
+  }
+
+  @Test
+  @SuppressWarnings("unchecked")
+  public void testInlineUnion_CardVariant_Serialization() {
+    TestCardParams card = new TestCardParams();
+    card.number = "4242424242424242";
+    card.expMonth = 12L;
+
+    TestInlineParams params = new TestInlineParams();
+    params.type = "card";
+    params.card = card;
+
+    Map<String, Object> map = converter.convert(params);
+    assertEquals("card", map.get("type"));
+
+    Map<String, Object> cardMap = (Map<String, Object>) map.get("card");
+    assertEquals("4242424242424242", cardMap.get("number"));
+    assertEquals(12L, cardMap.get("exp_month"));
+
+    // Non-selected variant is not present in serialized output.
+    assertEquals(null, map.get("bank"));
+  }
+
+  @Test
+  @SuppressWarnings("unchecked")
+  public void testInlineUnion_BankVariant_Serialization() {
+    TestBankParams bank = new TestBankParams();
+    bank.routingNumber = "110000000";
+    bank.accountNumber = "000123456789";
+
+    TestInlineParams params = new TestInlineParams();
+    params.type = "bank";
+    params.bank = bank;
+
+    Map<String, Object> map = converter.convert(params);
+    assertEquals("bank", map.get("type"));
+
+    Map<String, Object> bankMap = (Map<String, Object>) map.get("bank");
+    assertEquals("110000000", bankMap.get("routing_number"));
+    assertEquals("000123456789", bankMap.get("account_number"));
+  }
+
+  // ---------------------------------------------------------------------------
+  // Tests — response side (JSON → object)
+  // ---------------------------------------------------------------------------
+
+  @Test
+  public void testStandaloneUnion_RgbVariant_Deserialization() {
+    String json =
+        "{\"color\": {\"model\": \"rgb\", \"r\": 255, \"g\": 128, \"b\": 0}, \"name\": \"sunset\"}";
+
+    TestColorContainer container = testGson.fromJson(json, TestColorContainer.class);
+
+    assertEquals("sunset", container.name);
+    assertTrue(container.color instanceof TestRgbColorEntity);
+    TestRgbColorEntity rgb = (TestRgbColorEntity) container.color;
+    assertEquals("rgb", rgb.model);
+    assertEquals(Long.valueOf(255L), rgb.r);
+    assertEquals(Long.valueOf(128L), rgb.g);
+    assertEquals(Long.valueOf(0L), rgb.b);
+  }
+
+  @Test
+  public void testStandaloneUnion_HsvVariant_Deserialization() {
+    String json =
+        "{\"color\": {\"model\": \"hsv\", \"h\": 30, \"s\": 100, \"v\": 50}, \"name\": \"orange\"}";
+
+    TestColorContainer container = testGson.fromJson(json, TestColorContainer.class);
+
+    assertEquals("orange", container.name);
+    assertTrue(container.color instanceof TestHsvColorEntity);
+    TestHsvColorEntity hsv = (TestHsvColorEntity) container.color;
+    assertEquals("hsv", hsv.model);
+    assertEquals(Long.valueOf(30L), hsv.h);
+    assertEquals(Long.valueOf(100L), hsv.s);
+    assertEquals(Long.valueOf(50L), hsv.v);
+  }
+
+  @Test
+  public void testInlineUnion_CardVariant_Deserialization() {
+    String json =
+        "{\"type\": \"card\", \"card\": {\"number\": \"4242424242424242\", \"exp_month\": 12}}";
+
+    TestPaymentEntity entity = ApiResource.GSON.fromJson(json, TestPaymentEntity.class);
+
+    assertEquals("card", entity.type);
+    assertEquals("4242424242424242", entity.card.number);
+    assertEquals(Long.valueOf(12L), entity.card.expMonth);
+
+    // Non-selected variant remains null.
+    assertEquals(null, entity.bank);
+  }
+}