Add tests for missing extensions

Author: markmur

protocol/languages/kotlin/embedded-checkout-protocol/src/test/java/com/shopify/ucp/embedded/checkout/ExtensionPreservationTest.kt

@@ -0,0 +1,44 @@
+package com.shopify.ucp.embedded.checkout
+
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Test
+
+class ExtensionPreservationTest {
+
+    private val json = Json { ignoreUnknownKeys = true }
+
+    @Test
+    fun `preserves unknown extension keys on Signals`() {
+        val wire = """{"dev.ucp.buyer_ip":"203.0.113.7","com.example.device_id":"abc-123"}"""
+
+        val signals = json.decodeFromString(Signals.serializer(), wire)
+        val reEncoded = json.parseToJsonElement(json.encodeToString(Signals.serializer(), signals)).jsonObject
+
+        assertThat(reEncoded["dev.ucp.buyer_ip"]?.jsonPrimitive?.content).isEqualTo("203.0.113.7")
+        assertThat(reEncoded["com.example.device_id"]?.jsonPrimitive?.content).isEqualTo("abc-123")
+    }
+
+    @Test
+    fun `preserves unknown extension keys on Checkout`() {
+        val wire = """
+            {
+              "id": "checkout-123",
+              "currency": "USD",
+              "line_items": [],
+              "links": [],
+              "status": "incomplete",
+              "totals": [],
+              "ucp": {"payment_handlers": {}, "version": "2026-04-08"},
+              "com.example.foo": "bar"
+            }
+        """.trimIndent()
+
+        val checkout = json.decodeFromString(Checkout.serializer(), wire)
+        val reEncoded = json.parseToJsonElement(json.encodeToString(Checkout.serializer(), checkout)).jsonObject
+
+        assertThat(reEncoded["com.example.foo"]?.jsonPrimitive?.content).isEqualTo("bar")
+    }
+}

protocol/languages/swift/Tests/EmbeddedCheckoutProtocolTests/ModelDecodingTests.swift

@@ -153,6 +153,38 @@ struct ModelDecodingTests {
         #expect(colorScheme == [.light, .dark])
         #expect(config.delegate == ["window.open"])
     }
+
+    @Test func preservesUnknownExtensionKeysOnSignals() throws {
+        let json = """
+        {"dev.ucp.buyer_ip":"203.0.113.7","com.example.device_id":"abc-123"}
+        """
+        let signals = try JSONDecoder().decode(Signals.self, from: Data(json.utf8))
+        let reEncoded = try JSONEncoder().encode(signals)
+        let object = try #require(try JSONSerialization.jsonObject(with: reEncoded) as? [String: Any])
+
+        #expect(object["dev.ucp.buyer_ip"] as? String == "203.0.113.7")
+        #expect(object["com.example.device_id"] as? String == "abc-123")
+    }
+
+    @Test func preservesUnknownExtensionKeysOnCheckout() throws {
+        let json = """
+        {
+          "id": "checkout-123",
+          "currency": "USD",
+          "line_items": [],
+          "links": [],
+          "status": "incomplete",
+          "totals": [],
+          "ucp": {"payment_handlers": {}, "version": "2026-04-08"},
+          "com.example.foo": "bar"
+        }
+        """
+        let checkout = try JSONDecoder().decode(Checkout.self, from: Data(json.utf8))
+        let reEncoded = try JSONEncoder().encode(checkout)
+        let object = try #require(try JSONSerialization.jsonObject(with: reEncoded) as? [String: Any])
+
+        #expect(object["com.example.foo"] as? String == "bar")
+    }
 }
 
 private func fixtureString(_ name: String) throws -> String {

protocol/languages/typescript/test/extension-preservation.test.ts

@@ -0,0 +1,27 @@
+import {expect, test} from 'vitest';
+
+import {Convert} from '../src/generated/Models';
+
+test('preserves unknown top-level and nested extension keys through Convert round-trip', () => {
+  const wire = {
+    id: 'checkout-123',
+    currency: 'USD',
+    line_items: [],
+    links: [],
+    status: 'incomplete',
+    totals: [],
+    ucp: {payment_handlers: {}, version: '2026-04-08'},
+    signals: {
+      'dev.ucp.buyer_ip': '203.0.113.7',
+      'com.example.device_id': 'abc-123',
+    },
+    'com.example.foo': 'bar',
+  };
+
+  const checkout = Convert.toCheckout(JSON.stringify(wire));
+  const roundTripped = JSON.parse(Convert.checkoutToJson(checkout));
+
+  expect(roundTripped['com.example.foo']).toBe('bar');
+  expect(roundTripped.signals['dev.ucp.buyer_ip']).toBe('203.0.113.7');
+  expect(roundTripped.signals['com.example.device_id']).toBe('abc-123');
+});