test: Add an in-process MockSentryServer to sentry-test-support (#6266)

First step of moving the sample system tests into the modules they
cover. The server stands in for the Python mock server: it binds a free
port, accepts envelopes through the SDK's real HTTP transport, and lets
tests wait for a matching one.

The release-minified UI test APK pulls in sentry-test-support, so R8
needs to be told the JDK-only com.sun.net.httpserver classes are absent.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: runningcode

sentry-android-integration-tests/sentry-uitest-android/proguard-rules.pro

@@ -24,6 +24,7 @@
 
 -dontwarn com.google.errorprone.**
 -dontwarn com.sun.jna.**
+-dontwarn com.sun.net.httpserver.**
 -dontwarn edu.umd.cs.findbugs.**
 -dontwarn java.lang.instrument.**
 -dontwarn java.lang.management.**

sentry-test-support/build.gradle.kts

@@ -30,4 +30,6 @@ dependencies {
   implementation(kotlin(Config.kotlinStdLib))
   implementation(libs.kotlin.test.junit)
   implementation(libs.mockito.kotlin)
+
+  testImplementation(libs.google.truth)
 }

sentry-test-support/src/main/kotlin/io/sentry/test/MockSentryServer.kt

@@ -0,0 +1,87 @@
+package io.sentry.test
+
+import com.sun.net.httpserver.HttpExchange
+import com.sun.net.httpserver.HttpServer
+import io.sentry.JsonSerializer
+import io.sentry.SentryEnvelope
+import io.sentry.SentryOptions
+import io.sentry.time.Deadline
+import io.sentry.time.JavaMonotonicTicker
+import java.io.Closeable
+import java.net.InetAddress
+import java.net.InetSocketAddress
+import java.util.concurrent.CopyOnWriteArrayList
+import java.util.concurrent.TimeUnit
+import java.util.zip.GZIPInputStream
+
+/**
+ * A stand-in for Sentry's ingestion endpoint that integration tests point the SDK at through [dsn].
+ *
+ * Envelopes travel through the real HTTP transport, so serialization, compression and the DSN are
+ * covered too. It binds a free port so that test tasks running in parallel don't clash, and it
+ * works for an app in a child process as well as in the test's own JVM.
+ */
+class MockSentryServer : Closeable {
+  private val serializer = JsonSerializer(SentryOptions.empty())
+  private val received = CopyOnWriteArrayList<SentryEnvelope>()
+  private val server =
+    HttpServer.create(InetSocketAddress(InetAddress.getByName(HOST), 0), 0).apply {
+      createContext("/api/") { exchange -> receive(exchange) }
+      start()
+    }
+
+  val dsn: String = "http://key@$HOST:${server.address.port}/0"
+
+  val envelopes: List<SentryEnvelope>
+    get() = received.toList()
+
+  /** Returns the first received envelope matching [predicate], waiting up to [timeoutMillis]. */
+  fun awaitEnvelope(
+    timeoutMillis: Long = DEFAULT_TIMEOUT_MILLIS,
+    predicate: (SentryEnvelope) -> Boolean,
+  ): SentryEnvelope {
+    val deadline =
+      Deadline.after(JavaMonotonicTicker.getInstance(), timeoutMillis, TimeUnit.MILLISECONDS)
+    while (true) {
+      received.firstOrNull(predicate)?.let {
+        return it
+      }
+      if (deadline.hasPassed()) {
+        throw AssertionError(
+          "No matching envelope within ${timeoutMillis}ms, received ${received.size} envelopes"
+        )
+      }
+      Thread.sleep(POLL_INTERVAL_MILLIS)
+    }
+  }
+
+  fun reset() {
+    received.clear()
+  }
+
+  override fun close() {
+    server.stop(0)
+  }
+
+  private fun receive(exchange: HttpExchange) {
+    try {
+      val body =
+        if (exchange.requestHeaders.getFirst("Content-Encoding") == "gzip") {
+          GZIPInputStream(exchange.requestBody)
+        } else {
+          exchange.requestBody
+        }
+      serializer.deserializeEnvelope(body)?.let { received.add(it) }
+      exchange.sendResponseHeaders(200, -1)
+    } finally {
+      exchange.close()
+    }
+  }
+
+  private companion object {
+    // An IP rather than "localhost", which can resolve to IPv4 for the server and IPv6 for the SDK.
+    const val HOST = "127.0.0.1"
+    const val DEFAULT_TIMEOUT_MILLIS = 10_000L
+    const val POLL_INTERVAL_MILLIS = 50L
+  }
+}

sentry-test-support/src/test/kotlin/io/sentry/test/MockSentryServerTest.kt

@@ -0,0 +1,34 @@
+package io.sentry.test
+
+import com.google.common.truth.Truth.assertThat
+import io.sentry.Sentry
+import io.sentry.SentryItemType
+import kotlin.test.AfterTest
+import kotlin.test.Test
+import kotlin.test.assertFailsWith
+
+class MockSentryServerTest {
+  private val server = MockSentryServer()
+
+  @AfterTest
+  fun teardown() {
+    Sentry.close()
+    server.close()
+  }
+
+  @Test
+  fun `receives an event sent through the HTTP transport`() {
+    initForTest { it.dsn = server.dsn }
+
+    val eventId = Sentry.captureMessage("hello")
+    Sentry.flush(5000)
+
+    val envelope = server.awaitEnvelope { it.header.eventId == eventId }
+    assertThat(envelope.items.single().header.type).isEqualTo(SentryItemType.Event)
+  }
+
+  @Test
+  fun `awaitEnvelope fails once the timeout passes without a match`() {
+    assertFailsWith<AssertionError> { server.awaitEnvelope(timeoutMillis = 100) { true } }
+  }
+}