diff --git a/mockwebserver-deprecated/src/test/java/okhttp3/mockwebserver/MockWebServerTest.java b/mockwebserver-deprecated/src/test/java/okhttp3/mockwebserver/MockWebServerTest.java
index 7672d6426..462f7cfe1 100644
--- a/mockwebserver-deprecated/src/test/java/okhttp3/mockwebserver/MockWebServerTest.java
+++ b/mockwebserver-deprecated/src/test/java/okhttp3/mockwebserver/MockWebServerTest.java
@@ -50,17 +50,14 @@ import org.junit.jupiter.api.Timeout;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.runner.Description;
 import org.junit.runners.model.Statement;
-
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.Arrays.asList;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;
 import static org.junit.jupiter.api.Assertions.fail;
-import static org.junit.jupiter.api.Assumptions.assumeFalse;
 
 @SuppressWarnings({"ArraysAsListWithZeroOrOneArgument", "deprecation"})
 @Timeout(30)
@@ -71,7 +68,6 @@ public final class MockWebServerTest {
   private final MockWebServer server = new MockWebServer();
 
   @BeforeEach public void setUp() throws IOException {
-    platform.assumeNotBouncyCastle();
     server.start();
   }
 
@@ -540,7 +536,7 @@ public final class MockWebServerTest {
   }
 
   @Test public void https() throws Exception {
-    HandshakeCertificates handshakeCertificates = localhost();
+    HandshakeCertificates handshakeCertificates = platform.localhostHandshakeCertificates();
     server.useHttps(handshakeCertificates.sslSocketFactory(), false);
     server.enqueue(new MockResponse().setBody("abc"));
 
@@ -566,7 +562,8 @@ public final class MockWebServerTest {
   }
 
   @Test public void httpsWithClientAuth() throws Exception {
-    assumeFalse(getPlatform().equals("conscrypt"));
+    platform.assumeNotBouncyCastle();
+    platform.assumeNotConscrypt();
 
     HeldCertificate clientCa = new HeldCertificate.Builder()
         .certificateAuthority(0)
diff --git a/mockwebserver/src/test/java/mockwebserver3/MockWebServerTest.kt b/mockwebserver/src/test/java/mockwebserver3/MockWebServerTest.kt
index f58c8fc21..39e9ed91a 100644
--- a/mockwebserver/src/test/java/mockwebserver3/MockWebServerTest.kt
+++ b/mockwebserver/src/test/java/mockwebserver3/MockWebServerTest.kt
@@ -25,7 +25,6 @@ import java.net.ProtocolException
 import java.net.SocketTimeoutException
 import java.nio.charset.StandardCharsets.UTF_8
 import java.time.Duration
-import java.util.Arrays
 import java.util.concurrent.TimeUnit
 import javax.net.ssl.HttpsURLConnection
 import okhttp3.Headers
@@ -38,13 +37,11 @@ import okhttp3.TestUtil.assumeNotWindows
 import okhttp3.testing.PlatformRule
 import okhttp3.tls.HandshakeCertificates
 import okhttp3.tls.HeldCertificate
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.Buffer
 import org.assertj.core.api.Assertions.assertThat
 import org.assertj.core.data.Offset
 import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Assertions.fail
-import org.junit.jupiter.api.Assumptions
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Tag
@@ -64,7 +61,6 @@ class MockWebServerTest {
   @BeforeEach
   fun setUp(server: MockWebServer) {
     this.server = server
-    platform.assumeNotBouncyCastle()
     server.start()
   }
 
@@ -564,7 +560,7 @@ class MockWebServerTest {
 
   @Test
   fun https() {
-    val handshakeCertificates = localhost()
+    val handshakeCertificates = platform.localhostHandshakeCertificates()
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse.Builder()
       .body("abc")
@@ -589,7 +585,9 @@ class MockWebServerTest {
 
   @Test
   fun httpsWithClientAuth() {
-    Assumptions.assumeFalse(getPlatform() == "conscrypt")
+    platform.assumeNotBouncyCastle()
+    platform.assumeNotConscrypt()
+
     val clientCa = HeldCertificate.Builder()
       .certificateAuthority(0)
       .build()
diff --git a/okhttp-logging-interceptor/src/test/java/okhttp3/logging/HttpLoggingInterceptorTest.java b/okhttp-logging-interceptor/src/test/java/okhttp3/logging/HttpLoggingInterceptorTest.java
index 32e2127fd..367563276 100644
--- a/okhttp-logging-interceptor/src/test/java/okhttp3/logging/HttpLoggingInterceptorTest.java
+++ b/okhttp-logging-interceptor/src/test/java/okhttp3/logging/HttpLoggingInterceptorTest.java
@@ -45,9 +45,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.api.extension.RegisterExtension;
-
 import static okhttp3.RequestBody.gzip;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.fail;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
@@ -59,7 +57,8 @@ public final class HttpLoggingInterceptorTest {
   @RegisterExtension public final PlatformRule platform = new PlatformRule();
   private MockWebServer server;
 
-  private final HandshakeCertificates handshakeCertificates = localhost();
+  private final HandshakeCertificates handshakeCertificates
+    = platform.localhostHandshakeCertificates();
   private final HostnameVerifier hostnameVerifier = new RecordingHostnameVerifier();
   private OkHttpClient client;
   private String host;
@@ -848,8 +847,6 @@ public final class HttpLoggingInterceptorTest {
   }
 
   @Test public void http2() throws Exception {
-    platform.assumeNotBouncyCastle();
-
     server.useHttps(handshakeCertificates.sslSocketFactory());
     url = server.url("/");
 
@@ -930,7 +927,6 @@ public final class HttpLoggingInterceptorTest {
 
   @Test public void duplexRequestsAreNotLogged() throws Exception {
     platform.assumeHttp2Support();
-    platform.assumeNotBouncyCastle();
 
     server.useHttps(handshakeCertificates.sslSocketFactory()); // HTTP/2
     url = server.url("/");
diff --git a/okhttp-logging-interceptor/src/test/java/okhttp3/logging/LoggingEventListenerTest.java b/okhttp-logging-interceptor/src/test/java/okhttp3/logging/LoggingEventListenerTest.java
index 1d274942b..54e4b5fc4 100644
--- a/okhttp-logging-interceptor/src/test/java/okhttp3/logging/LoggingEventListenerTest.java
+++ b/okhttp-logging-interceptor/src/test/java/okhttp3/logging/LoggingEventListenerTest.java
@@ -37,11 +37,9 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.api.extension.RegisterExtension;
-
 import static java.util.Arrays.asList;
 import static okhttp3.Protocol.HTTP_1_1;
 import static okhttp3.Protocol.HTTP_2;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.fail;
 
@@ -53,7 +51,8 @@ public final class LoggingEventListenerTest {
   @RegisterExtension public final OkHttpClientTestRule clientTestRule = new OkHttpClientTestRule();
   private MockWebServer server;
 
-  private final HandshakeCertificates handshakeCertificates = localhost();
+  private final HandshakeCertificates handshakeCertificates
+    = platform.localhostHandshakeCertificates();
   private final LogRecorder logRecorder = new LogRecorder();
   private final LoggingEventListener.Factory loggingEventListenerFactory =
       new LoggingEventListener.Factory(logRecorder);
@@ -153,7 +152,6 @@ public final class LoggingEventListenerTest {
   @Test
   public void secureGet() throws Exception {
     TestUtil.assumeNotWindows();
-    platform.assumeNotBouncyCastle();
 
     server.useHttps(handshakeCertificates.sslSocketFactory());
     url = server.url("/");
@@ -222,7 +220,6 @@ public final class LoggingEventListenerTest {
   @Test
   public void connectFail() {
     TestUtil.assumeNotWindows();
-    platform.assumeNotBouncyCastle();
 
     server.useHttps(handshakeCertificates.sslSocketFactory());
     server.setProtocols(asList(HTTP_2, HTTP_1_1));
@@ -246,9 +243,9 @@ public final class LoggingEventListenerTest {
         .assertLogMatch("connectStart: " + url.host() + "/.+ DIRECT")
         .assertLogMatch("secureConnectStart")
         .assertLogMatch(
-            "connectFailed: null javax\\.net\\.ssl\\.(?:SSLProtocolException|SSLHandshakeException): (?:Unexpected handshake message: client_hello|Handshake message sequence violation, 1|Read error|Handshake failed).*")
+            "connectFailed: null \\S+(?:SSLProtocolException|SSLHandshakeException|TlsFatalAlert): (?:Unexpected handshake message: client_hello|Handshake message sequence violation, 1|Read error|Handshake failed|unexpected_message\\(10\\)).*")
         .assertLogMatch(
-            "callFailed: javax\\.net\\.ssl\\.(?:SSLProtocolException|SSLHandshakeException): (?:Unexpected handshake message: client_hello|Handshake message sequence violation, 1|Read error|Handshake failed).*")
+            "callFailed: \\S+(?:SSLProtocolException|SSLHandshakeException|TlsFatalAlert): (?:Unexpected handshake message: client_hello|Handshake message sequence violation, 1|Read error|Handshake failed|unexpected_message\\(10\\)).*")
         .assertNoMoreLogs();
   }
 
diff --git a/okhttp-testing-support/src/main/kotlin/okhttp3/testing/PlatformRule.kt b/okhttp-testing-support/src/main/kotlin/okhttp3/testing/PlatformRule.kt
index 22e696d1a..5b93521eb 100644
--- a/okhttp-testing-support/src/main/kotlin/okhttp3/testing/PlatformRule.kt
+++ b/okhttp-testing-support/src/main/kotlin/okhttp3/testing/PlatformRule.kt
@@ -18,12 +18,18 @@ package okhttp3.testing
 import android.os.Build
 import com.amazon.corretto.crypto.provider.AmazonCorrettoCryptoProvider
 import com.amazon.corretto.crypto.provider.SelfTestStatus
+import java.lang.reflect.Method
+import java.net.InetAddress
+import java.security.Security
 import okhttp3.TestUtil
 import okhttp3.internal.platform.ConscryptPlatform
 import okhttp3.internal.platform.Jdk8WithJettyBootPlatform
 import okhttp3.internal.platform.Jdk9Platform
 import okhttp3.internal.platform.OpenJSSEPlatform
 import okhttp3.internal.platform.Platform
+import okhttp3.tls.HandshakeCertificates
+import okhttp3.tls.HeldCertificate
+import okhttp3.tls.internal.TlsUtil.localhost
 import org.bouncycastle.jce.provider.BouncyCastleProvider
 import org.bouncycastle.jsse.provider.BouncyCastleJsseProvider
 import org.conscrypt.Conscrypt
@@ -43,8 +49,6 @@ import org.junit.jupiter.api.extension.InvocationInterceptor
 import org.junit.jupiter.api.extension.ReflectiveInvocationContext
 import org.openjsse.net.ssl.OpenJSSE
 import org.opentest4j.TestAbortedException
-import java.lang.reflect.Method
-import java.security.Security
 
 /**
  * Marks a test as Platform aware, before the test runs a consistent Platform will be
@@ -323,6 +327,13 @@ open class PlatformRule @JvmOverloads constructor(
     }
   }
 
+  fun localhostHandshakeCertificates(): HandshakeCertificates {
+    return when {
+      isBouncyCastle() -> localhostHandshakeCertificatesWithRsa2048
+      else -> localhost()
+    }
+  }
+
   val isAndroid: Boolean
     get() = Platform.Companion.isAndroid
 
@@ -336,6 +347,24 @@ open class PlatformRule @JvmOverloads constructor(
     const val OPENJSSE_PROPERTY = "openjsse"
     const val BOUNCYCASTLE_PROPERTY = "bouncycastle"
 
+    /**
+     * For whatever reason our BouncyCastle provider doesn't work with ECDSA keys. Just configure it
+     * to use RSA-2048 instead.
+     *
+     * (We otherwise prefer ECDSA because it's faster.)
+     */
+    private val localhostHandshakeCertificatesWithRsa2048: HandshakeCertificates by lazy {
+      val heldCertificate = HeldCertificate.Builder()
+        .commonName("localhost")
+        .addSubjectAlternativeName(InetAddress.getByName("localhost").canonicalHostName)
+        .rsa2048()
+        .build()
+      return@lazy HandshakeCertificates.Builder()
+        .heldCertificate(heldCertificate)
+        .addTrustedCertificate(heldCertificate.certificate)
+        .build()
+    }
+
     init {
       val platformSystemProperty = getPlatformSystemProperty()
 
diff --git a/okhttp-tls/src/test/java/okhttp3/tls/HandshakeCertificatesTest.kt b/okhttp-tls/src/test/java/okhttp3/tls/HandshakeCertificatesTest.kt
index 5c31ff7fc..8f9565185 100644
--- a/okhttp-tls/src/test/java/okhttp3/tls/HandshakeCertificatesTest.kt
+++ b/okhttp-tls/src/test/java/okhttp3/tls/HandshakeCertificatesTest.kt
@@ -56,6 +56,7 @@ class HandshakeCertificatesTest {
   @Test fun clientAndServer() {
     platform.assumeNotConscrypt()
     platform.assumeNotBouncyCastle()
+
     val clientRoot = HeldCertificate.Builder()
       .certificateAuthority(1)
       .build()
diff --git a/okhttp/src/jvmTest/java/okhttp3/CacheCorruptionTest.kt b/okhttp/src/jvmTest/java/okhttp3/CacheCorruptionTest.kt
index 86e619a69..802512e25 100644
--- a/okhttp/src/jvmTest/java/okhttp3/CacheCorruptionTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/CacheCorruptionTest.kt
@@ -31,7 +31,6 @@ import okhttp3.Headers.Companion.headersOf
 import okhttp3.internal.buildCache
 import okhttp3.okio.LoggingFilesystem
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.Path.Companion.toPath
 import okio.fakefilesystem.FakeFileSystem
 import org.assertj.core.api.Assertions.assertThat
@@ -51,7 +50,7 @@ class CacheCorruptionTest {
   @RegisterExtension
   val platform = PlatformRule()
 
-  private val handshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
   private lateinit var client: OkHttpClient
   private lateinit var cache: Cache
   private val NULL_HOSTNAME_VERIFIER = HostnameVerifier { _: String?, _: SSLSession? -> true }
@@ -63,7 +62,6 @@ class CacheCorruptionTest {
     this.server = server
 
     platform.assumeNotOpenJSSE()
-    platform.assumeNotBouncyCastle()
     server.protocolNegotiationEnabled = false
     val loggingFileSystem = LoggingFilesystem(fileSystem)
     cache = buildCache("/cache/".toPath(), Int.MAX_VALUE.toLong(), loggingFileSystem)
diff --git a/okhttp/src/jvmTest/java/okhttp3/CacheTest.java b/okhttp/src/jvmTest/java/okhttp3/CacheTest.java
index 83e299164..c285312fd 100644
--- a/okhttp/src/jvmTest/java/okhttp3/CacheTest.java
+++ b/okhttp/src/jvmTest/java/okhttp3/CacheTest.java
@@ -58,7 +58,6 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import static mockwebserver3.SocketPolicy.DISCONNECT_AT_END;
 import static okhttp3.internal.Internal.cacheGet;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -73,7 +72,8 @@ public final class CacheTest {
 
   private MockWebServer server;
   private MockWebServer server2;
-  private final HandshakeCertificates handshakeCertificates = localhost();
+  private final HandshakeCertificates handshakeCertificates
+    = platform.localhostHandshakeCertificates();
   private OkHttpClient client;
   private Cache cache;
   private final CookieManager cookieManager = new CookieManager();
@@ -87,7 +87,6 @@ public final class CacheTest {
     this.server2 = server2;
 
     platform.assumeNotOpenJSSE();
-    platform.assumeNotBouncyCastle();
 
     server.setProtocolNegotiationEnabled(false);
     fileSystem.emulateUnix();
diff --git a/okhttp/src/jvmTest/java/okhttp3/CallHandshakeTest.kt b/okhttp/src/jvmTest/java/okhttp3/CallHandshakeTest.kt
index 2c06c4fce..77da163fa 100644
--- a/okhttp/src/jvmTest/java/okhttp3/CallHandshakeTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/CallHandshakeTest.kt
@@ -31,7 +31,6 @@ import okhttp3.CipherSuite.Companion.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
 import okhttp3.internal.effectiveCipherSuites
 import okhttp3.internal.platform.Platform
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil.localhost
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
@@ -40,7 +39,6 @@ import org.junit.jupiter.api.extension.RegisterExtension
 class CallHandshakeTest {
   private lateinit var client: OkHttpClient
   private lateinit var server: MockWebServer
-  val handshakeCertificates = localhost()
 
   @RegisterExtension
   @JvmField
@@ -50,6 +48,8 @@ class CallHandshakeTest {
   @JvmField
   var platform = PlatformRule()
 
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
+
   private lateinit var handshakeEnabledCipherSuites: List<String>
   private lateinit var defaultEnabledCipherSuites: List<String>
   private lateinit var defaultSupportedCipherSuites: List<String>
@@ -131,9 +131,7 @@ class CallHandshakeTest {
 
   @Test
   fun testDefaultHandshakeCipherSuiteOrderingTls13Modern() {
-    // handshake_failure(40)
-    // org.bouncycastle.tls.TlsFatalAlertReceived: handshake_failure(40)
-    //	at app//org.bouncycastle.tls.TlsProtocol.handleAlertMessage(Unknown Source)
+    // We are avoiding making guarantees on ordering of secondary Platforms.
     platform.assumeNotBouncyCastle()
 
     val client = makeClient(ConnectionSpec.MODERN_TLS, TlsVersion.TLS_1_3)
@@ -162,10 +160,6 @@ class CallHandshakeTest {
 
   @Test
   fun testHandshakeCipherSuiteOrderingWhenReversed() {
-    // handshake_failure(40)
-    // org.bouncycastle.tls.TlsFatalAlertReceived: handshake_failure(40)
-    //	at app//org.bouncycastle.tls.TlsProtocol.handleAlertMessage(Unknown Source)
-
     // We are avoiding making guarantees on ordering of secondary Platforms.
     platform.assumeNotConscrypt()
     platform.assumeNotBouncyCastle()
@@ -185,11 +179,6 @@ class CallHandshakeTest {
 
   @Test
   fun defaultOrderMaintained() {
-    // Flaky in CI
-    // CallHandshakeTest[jvm] > defaultOrderMaintained()[jvm] FAILED
-    //  org.bouncycastle.tls.TlsFatalAlertReceived: handshake_failure(40)
-    platform.assumeNotBouncyCastle()
-
     val client = makeClient()
     makeRequest(client)
 
diff --git a/okhttp/src/jvmTest/java/okhttp3/CallKotlinTest.kt b/okhttp/src/jvmTest/java/okhttp3/CallKotlinTest.kt
index 668643461..1edd927b3 100644
--- a/okhttp/src/jvmTest/java/okhttp3/CallKotlinTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/CallKotlinTest.kt
@@ -32,7 +32,6 @@ import okhttp3.internal.connection.RealConnection.Companion.IDLE_CONNECTION_HEAL
 import okhttp3.internal.http.RecordingProxySelector
 import okhttp3.testing.Flaky
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.BufferedSink
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Assertions.assertEquals
@@ -52,13 +51,12 @@ class CallKotlinTest {
   }
 
   private var client = clientTestRule.newClient()
-  private val handshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
   private lateinit var server: MockWebServer
 
   @BeforeEach
   fun setUp(server: MockWebServer) {
     this.server = server
-    platform.assumeNotBouncyCastle()
   }
 
   @Test
diff --git a/okhttp/src/jvmTest/java/okhttp3/CallTest.kt b/okhttp/src/jvmTest/java/okhttp3/CallTest.kt
index be756609b..c662f6bb3 100644
--- a/okhttp/src/jvmTest/java/okhttp3/CallTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/CallTest.kt
@@ -75,7 +75,6 @@ import okhttp3.testing.Flaky
 import okhttp3.testing.PlatformRule
 import okhttp3.tls.HandshakeCertificates
 import okhttp3.tls.HeldCertificate
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.Buffer
 import okio.BufferedSink
 import okio.ForwardingSource
@@ -88,7 +87,7 @@ import org.assertj.core.data.Offset
 import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Assertions.assertArrayEquals
 import org.junit.jupiter.api.Assertions.fail
-import org.junit.jupiter.api.Assumptions
+import org.junit.jupiter.api.Assumptions.assumeFalse
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Tag
@@ -114,7 +113,7 @@ open class CallTest {
   private lateinit var server2: MockWebServer
 
   private var listener = RecordingEventListener()
-  private val handshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
   private var client = clientTestRule.newClientBuilder()
     .eventListenerFactory(clientTestRule.wrap(listener))
     .build()
@@ -134,7 +133,6 @@ open class CallTest {
     this.server2 = server2
 
     platform.assumeNotOpenJSSE()
-    platform.assumeNotBouncyCastle()
   }
 
   @AfterEach
@@ -1205,6 +1203,8 @@ open class CallTest {
 
   @Test
   fun tlsHandshakeFailure_noFallbackByDefault() {
+    platform.assumeNotBouncyCastle()
+
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
     server.enqueue(MockResponse(body = "response that will never be received"))
@@ -1219,6 +1219,8 @@ open class CallTest {
 
   @Test
   fun recoverFromTlsHandshakeFailure() {
+    platform.assumeNotBouncyCastle()
+
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
     server.enqueue(MockResponse(body = "abc"))
@@ -1271,6 +1273,8 @@ open class CallTest {
 
   @Test
   fun recoverFromTlsHandshakeFailure_Async() {
+    platform.assumeNotBouncyCastle()
+
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
     server.enqueue(MockResponse(body = "abc"))
@@ -1291,6 +1295,8 @@ open class CallTest {
 
   @Test
   fun noRecoveryFromTlsHandshakeFailureWhenTlsFallbackIsDisabled() {
+    platform.assumeNotBouncyCastle()
+
     client = client.newBuilder()
       .connectionSpecs(listOf(ConnectionSpec.MODERN_TLS, ConnectionSpec.CLEARTEXT))
       .hostnameVerifier(RecordingHostnameVerifier())
@@ -1319,6 +1325,8 @@ open class CallTest {
   @Test
   fun tlsHostnameVerificationFailure() {
     assumeNotWindows()
+    platform.assumeNotBouncyCastle()
+
     server.enqueue(MockResponse())
     val serverCertificate = HeldCertificate.Builder()
       .commonName("localhost") // Unusued for hostname verification.
@@ -1345,9 +1353,10 @@ open class CallTest {
   @Test
   fun anonCipherSuiteUnsupported() {
     platform.assumeNotConscrypt()
+    platform.assumeNotBouncyCastle()
 
     // The _anon_ suites became unsupported in "1.8.0_201" and "11.0.2".
-    Assumptions.assumeFalse(
+    assumeFalse(
       System.getProperty("java.version", "unknown").matches(Regex("1\\.8\\.0_1\\d\\d"))
     )
     server.enqueue(MockResponse())
@@ -3964,6 +3973,8 @@ open class CallTest {
 
   @Test
   fun httpsWithIpAddress() {
+    platform.assumeNotBouncyCastle()
+
     val localIpAddress = InetAddress.getLoopbackAddress().hostAddress
 
     // Create a certificate with an IP address in the subject alt name.
diff --git a/okhttp/src/jvmTest/java/okhttp3/ConnectionReuseTest.kt b/okhttp/src/jvmTest/java/okhttp3/ConnectionReuseTest.kt
index 9e51d3a00..4db61c8ac 100644
--- a/okhttp/src/jvmTest/java/okhttp3/ConnectionReuseTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/ConnectionReuseTest.kt
@@ -27,8 +27,8 @@ import okhttp3.ResponseBody.Companion.toResponseBody
 import okhttp3.internal.closeQuietly
 import okhttp3.testing.PlatformRule
 import okhttp3.tls.HandshakeCertificates
-import okhttp3.tls.internal.TlsUtil.localhost
 import org.assertj.core.api.Assertions.assertThat
+import org.bouncycastle.tls.TlsFatalAlert
 import org.junit.jupiter.api.Assertions.fail
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Tag
@@ -46,7 +46,7 @@ class ConnectionReuseTest {
   val clientTestRule: OkHttpClientTestRule = OkHttpClientTestRule()
 
   private lateinit var server: MockWebServer
-  private val handshakeCertificates: HandshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
   private var client: OkHttpClient = clientTestRule.newClient()
 
   @BeforeEach
@@ -75,7 +75,6 @@ class ConnectionReuseTest {
 
   @Test
   fun connectionsAreReusedWithHttp2() {
-    platform.assumeNotBouncyCastle()
     enableHttp2()
     server.enqueue(MockResponse(body = "a"))
     server.enqueue(MockResponse(body = "b"))
@@ -191,7 +190,6 @@ class ConnectionReuseTest {
 
   @Test
   fun http2ConnectionsAreSharedBeforeResponseIsConsumed() {
-    platform.assumeNotBouncyCastle()
     enableHttp2()
     server.enqueue(MockResponse(body = "a"))
     server.enqueue(MockResponse(body = "b"))
@@ -225,7 +223,6 @@ class ConnectionReuseTest {
 
   @Test
   fun connectionsAreNotReusedIfSslSocketFactoryChanges() {
-    platform.assumeNotBouncyCastle()
     enableHttps()
     server.enqueue(MockResponse())
     server.enqueue(MockResponse())
@@ -246,12 +243,12 @@ class ConnectionReuseTest {
       anotherClient.newCall(request).execute()
       fail<Any?>()
     } catch (expected: SSLException) {
+    } catch (expected: TlsFatalAlert) {
     }
   }
 
   @Test
   fun connectionsAreNotReusedIfHostnameVerifierChanges() {
-    platform.assumeNotBouncyCastle()
     enableHttps()
     server.enqueue(MockResponse())
     server.enqueue(MockResponse())
diff --git a/okhttp/src/jvmTest/java/okhttp3/DuplexTest.java b/okhttp/src/jvmTest/java/okhttp3/DuplexTest.java
index 82ab6925f..c49a31c39 100644
--- a/okhttp/src/jvmTest/java/okhttp3/DuplexTest.java
+++ b/okhttp/src/jvmTest/java/okhttp3/DuplexTest.java
@@ -43,7 +43,6 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.Timeout;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import static java.util.Arrays.asList;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -56,7 +55,8 @@ public final class DuplexTest {
 
   private MockWebServer server;
   private RecordingEventListener listener = new RecordingEventListener();
-  private final HandshakeCertificates handshakeCertificates = localhost();
+  private final HandshakeCertificates handshakeCertificates
+    = platform.localhostHandshakeCertificates();
   private OkHttpClient client = clientTestRule.newClientBuilder()
       .eventListenerFactory(clientTestRule.wrap(listener))
       .build();
@@ -67,7 +67,6 @@ public final class DuplexTest {
     this.server = server;
     platform.assumeNotOpenJSSE();
     platform.assumeHttp2Support();
-    platform.assumeNotBouncyCastle();
   }
 
   @AfterEach public void tearDown() {
diff --git a/okhttp/src/jvmTest/java/okhttp3/EventListenerTest.java b/okhttp/src/jvmTest/java/okhttp3/EventListenerTest.java
index b586ef64a..78b1174f6 100644
--- a/okhttp/src/jvmTest/java/okhttp3/EventListenerTest.java
+++ b/okhttp/src/jvmTest/java/okhttp3/EventListenerTest.java
@@ -74,7 +74,6 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.Timeout;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import static java.util.Arrays.asList;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.hamcrest.CoreMatchers.any;
 import static org.hamcrest.CoreMatchers.equalTo;
@@ -92,7 +91,8 @@ public final class EventListenerTest {
 
   private MockWebServer server;
   private final RecordingEventListener listener = new RecordingEventListener();
-  private final HandshakeCertificates handshakeCertificates = localhost();
+  private final HandshakeCertificates handshakeCertificates
+    = platform.localhostHandshakeCertificates();
 
   private OkHttpClient client = clientTestRule.newClientBuilder()
       .eventListenerFactory(clientTestRule.wrap(listener))
@@ -104,7 +104,6 @@ public final class EventListenerTest {
     this.server = server;
 
     platform.assumeNotOpenJSSE();
-    platform.assumeNotBouncyCastle();
 
     listener.forbidLock(RealConnectionPool.Companion.get(client.connectionPool()));
     listener.forbidLock(client.dispatcher());
diff --git a/okhttp/src/jvmTest/java/okhttp3/InsecureForHostTest.kt b/okhttp/src/jvmTest/java/okhttp3/InsecureForHostTest.kt
index 8e5f65932..59a015e39 100644
--- a/okhttp/src/jvmTest/java/okhttp3/InsecureForHostTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/InsecureForHostTest.kt
@@ -21,7 +21,6 @@ import mockwebserver3.MockWebServer
 import okhttp3.testing.PlatformRule
 import okhttp3.tls.HandshakeCertificates
 import okhttp3.tls.HeldCertificate
-import okhttp3.tls.internal.TlsUtil.localhost
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
@@ -43,7 +42,7 @@ class InsecureForHostTest {
   }
 
   @Test fun `untrusted host in insecureHosts connects successfully`() {
-    val serverCertificates = localhost()
+    val serverCertificates = platform.localhostHandshakeCertificates()
     server.useHttps(serverCertificates.sslSocketFactory())
     server.enqueue(MockResponse())
 
@@ -95,7 +94,7 @@ class InsecureForHostTest {
   }
 
   @Test fun `untrusted host not in insecureHosts fails with SSLException`() {
-    val serverCertificates = localhost()
+    val serverCertificates = platform.localhostHandshakeCertificates()
     server.useHttps(serverCertificates.sslSocketFactory())
     server.enqueue(MockResponse())
 
diff --git a/okhttp/src/jvmTest/java/okhttp3/JSSETest.kt b/okhttp/src/jvmTest/java/okhttp3/JSSETest.kt
index 381cd3015..ff1be19eb 100644
--- a/okhttp/src/jvmTest/java/okhttp3/JSSETest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/JSSETest.kt
@@ -15,13 +15,14 @@
  */
 package okhttp3
 
+import javax.net.ssl.SSLSocket
+import javax.net.ssl.SSLSocketFactory
 import mockwebserver3.MockResponse
 import mockwebserver3.MockWebServer
 import okhttp3.TestUtil.assumeNetwork
 import okhttp3.internal.connection
 import okhttp3.testing.PlatformRule
 import okhttp3.testing.PlatformVersion
-import okhttp3.tls.internal.TlsUtil
 import okio.ByteString.Companion.toByteString
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Assertions.assertEquals
@@ -30,14 +31,12 @@ import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.extension.RegisterExtension
-import javax.net.ssl.SSLSocket
-import javax.net.ssl.SSLSocketFactory
 
 class JSSETest {
   @JvmField @RegisterExtension var platform = PlatformRule()
   @JvmField @RegisterExtension val clientTestRule = OkHttpClientTestRule()
 
-  private val handshakeCertificates = TlsUtil.localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
 
   var client = clientTestRule.newClient()
 
diff --git a/okhttp/src/jvmTest/java/okhttp3/RouteFailureTest.kt b/okhttp/src/jvmTest/java/okhttp3/RouteFailureTest.kt
index 61f880e61..c478dd353 100644
--- a/okhttp/src/jvmTest/java/okhttp3/RouteFailureTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/RouteFailureTest.kt
@@ -24,7 +24,6 @@ import mockwebserver3.SocketPolicy
 import mockwebserver3.junit5.internal.MockWebServerInstance
 import okhttp3.internal.http2.ErrorCode
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil.localhost
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
@@ -45,7 +44,7 @@ class RouteFailureTest {
 
   private var listener = RecordingEventListener()
 
-  private val handshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
 
   val dns = FakeDns()
 
diff --git a/okhttp/src/jvmTest/java/okhttp3/ServerTruncatesRequestTest.kt b/okhttp/src/jvmTest/java/okhttp3/ServerTruncatesRequestTest.kt
index 4a38f604d..2e6ec1b1f 100644
--- a/okhttp/src/jvmTest/java/okhttp3/ServerTruncatesRequestTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/ServerTruncatesRequestTest.kt
@@ -23,7 +23,6 @@ import okhttp3.Headers.Companion.headersOf
 import okhttp3.internal.duplex.AsyncRequestBody
 import okhttp3.internal.http2.ErrorCode
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.BufferedSink
 import okio.IOException
 import org.assertj.core.api.Assertions.assertThat
@@ -47,7 +46,7 @@ class ServerTruncatesRequestTest {
   var clientTestRule = OkHttpClientTestRule()
 
   private val listener = RecordingEventListener()
-  private val handshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
 
   private var client = clientTestRule.newClientBuilder()
     .eventListenerFactory(clientTestRule.wrap(listener))
@@ -60,7 +59,6 @@ class ServerTruncatesRequestTest {
     this.server = server
     platform.assumeNotOpenJSSE()
     platform.assumeHttp2Support()
-    platform.assumeNotBouncyCastle()
   }
 
   @Test
diff --git a/okhttp/src/jvmTest/java/okhttp3/SessionReuseTest.kt b/okhttp/src/jvmTest/java/okhttp3/SessionReuseTest.kt
index fdeca595d..67e2ea478 100644
--- a/okhttp/src/jvmTest/java/okhttp3/SessionReuseTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/SessionReuseTest.kt
@@ -15,12 +15,12 @@
  */
 package okhttp3
 
+import javax.net.ssl.SSLSocket
 import mockwebserver3.MockResponse
 import mockwebserver3.MockWebServer
 import okhttp3.testing.Flaky
 import okhttp3.testing.PlatformRule
 import okhttp3.testing.PlatformVersion
-import okhttp3.tls.internal.TlsUtil
 import okio.ByteString.Companion.toByteString
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Assertions.assertEquals
@@ -30,13 +30,12 @@ import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.extension.RegisterExtension
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.ValueSource
-import javax.net.ssl.SSLSocket
 
 class SessionReuseTest {
   @JvmField @RegisterExtension var platform = PlatformRule()
   @JvmField @RegisterExtension val clientTestRule = OkHttpClientTestRule()
 
-  private val handshakeCertificates = TlsUtil.localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
 
   var client = clientTestRule.newClient()
 
@@ -50,9 +49,7 @@ class SessionReuseTest {
     // System.setProperty("jdk.tls.client.enableSessionTicketExtension", "true")
     // System.setProperty("jdk.tls.server.enableSessionTicketExtension", "true")
 
-    // Session reuse not tested
-    // org.bouncycastle.tls.TlsFatalAlert: handshake_failure(40); No selectable cipher suite
-    //	at org.bouncycastle.tls.AbstractTlsServer.getSelectedCipherSuite(Unknown Source)
+    // IllegalStateException: Cannot resume session and session creation is disabled
     platform.assumeNotBouncyCastle()
   }
 
diff --git a/okhttp/src/jvmTest/java/okhttp3/SocketChannelTest.kt b/okhttp/src/jvmTest/java/okhttp3/SocketChannelTest.kt
index b80ce5adc..51daa885b 100644
--- a/okhttp/src/jvmTest/java/okhttp3/SocketChannelTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/SocketChannelTest.kt
@@ -15,6 +15,15 @@
  */
 package okhttp3
 
+import java.io.IOException
+import java.net.InetAddress
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.TimeUnit.SECONDS
+import javax.net.ssl.SNIHostName
+import javax.net.ssl.SNIMatcher
+import javax.net.ssl.SNIServerName
+import javax.net.ssl.SSLSocket
+import javax.net.ssl.StandardConstants
 import mockwebserver3.MockResponse
 import mockwebserver3.MockWebServer
 import okhttp3.Protocol.HTTP_1_1
@@ -31,21 +40,12 @@ import okhttp3.tls.HeldCertificate
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Assumptions.assumeFalse
 import org.junit.jupiter.api.Assumptions.assumeTrue
+import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Tag
 import org.junit.jupiter.api.Timeout
 import org.junit.jupiter.api.extension.RegisterExtension
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.MethodSource
-import java.io.IOException
-import java.net.InetAddress
-import java.util.concurrent.CompletableFuture
-import java.util.concurrent.TimeUnit.SECONDS
-import javax.net.ssl.SNIHostName
-import javax.net.ssl.SNIMatcher
-import javax.net.ssl.SNIServerName
-import javax.net.ssl.SSLSocket
-import javax.net.ssl.StandardConstants
-import org.junit.jupiter.api.BeforeEach
 
 @Suppress("UsePropertyAccessSyntax")
 @Timeout(6)
diff --git a/okhttp/src/jvmTest/java/okhttp3/URLConnectionTest.kt b/okhttp/src/jvmTest/java/okhttp3/URLConnectionTest.kt
index 578e90ca7..a89ade7e2 100644
--- a/okhttp/src/jvmTest/java/okhttp3/URLConnectionTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/URLConnectionTest.kt
@@ -71,13 +71,13 @@ import okhttp3.internal.platform.Platform.Companion.get
 import okhttp3.internal.userAgent
 import okhttp3.testing.Flaky
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.Buffer
 import okio.BufferedSink
 import okio.GzipSink
 import okio.buffer
 import okio.utf8Size
 import org.assertj.core.api.Assertions.assertThat
+import org.bouncycastle.tls.TlsFatalAlert
 import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Assertions.fail
 import org.junit.jupiter.api.BeforeEach
@@ -102,7 +102,7 @@ class URLConnectionTest {
 
   private lateinit var server: MockWebServer
   private lateinit var server2: MockWebServer
-  private val handshakeCertificates = localhost()
+  private val handshakeCertificates = platform.localhostHandshakeCertificates()
   private var client = clientTestRule.newClient()
   private var cache: Cache? = null
 
@@ -110,7 +110,6 @@ class URLConnectionTest {
   fun setUp(server: MockWebServer, @MockWebServerInstance("server2") server2: MockWebServer) {
     this.server = server
     this.server2 = server2
-    platform.assumeNotBouncyCastle()
     server.protocolNegotiationEnabled = false
   }
 
@@ -571,12 +570,15 @@ class URLConnectionTest {
         "without an SSL socket factory, the connection should fail"
       )
     } catch (expected: SSLException) {
+    } catch (expected: TlsFatalAlert) {
     }
   }
 
   // TODO(jwilson): tests below this marker need to be migrated to OkHttp's request/response API.
   @Test
   fun connectViaHttpsWithSSLFallback() {
+    platform.assumeNotBouncyCastle()
+
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
     server.enqueue(MockResponse(body = "this response comes via SSL"))
@@ -600,6 +602,8 @@ class URLConnectionTest {
 
   @Test
   fun connectViaHttpsWithSSLFallbackFailuresRecorded() {
+    platform.assumeNotBouncyCastle()
+
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
@@ -679,6 +683,7 @@ class URLConnectionTest {
           CertificateException::class.java
         )
       }
+    } catch (expected: TlsFatalAlert) {
     }
     assertThat(server.requestCount).isEqualTo(0)
   }
@@ -3749,6 +3754,8 @@ class URLConnectionTest {
 
   @Test
   fun testNoSslFallback() {
+    platform.assumeNotBouncyCastle()
+
     server.useHttps(handshakeCertificates.sslSocketFactory())
     server.enqueue(MockResponse(socketPolicy = SocketPolicy.FAIL_HANDSHAKE))
     server.enqueue(MockResponse(body = "Response that would have needed fallbacks"))
diff --git a/okhttp/src/jvmTest/java/okhttp3/internal/http/CancelTest.kt b/okhttp/src/jvmTest/java/okhttp3/internal/http/CancelTest.kt
index 0b6fe4221..6174bbee1 100644
--- a/okhttp/src/jvmTest/java/okhttp3/internal/http/CancelTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/internal/http/CancelTest.kt
@@ -15,6 +15,13 @@
  */
 package okhttp3.internal.http
 
+import java.io.IOException
+import java.net.ServerSocket
+import java.net.Socket
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit.MILLISECONDS
+import javax.net.ServerSocketFactory
+import javax.net.SocketFactory
 import mockwebserver3.MockResponse
 import mockwebserver3.MockWebServer
 import okhttp3.Call
@@ -44,7 +51,6 @@ import okhttp3.internal.http.CancelTest.ConnectionType.H2
 import okhttp3.internal.http.CancelTest.ConnectionType.HTTP
 import okhttp3.internal.http.CancelTest.ConnectionType.HTTPS
 import okhttp3.testing.PlatformRule
-import okhttp3.tls.internal.TlsUtil
 import okio.Buffer
 import okio.BufferedSink
 import org.assertj.core.api.Assertions.assertThat
@@ -55,13 +61,6 @@ import org.junit.jupiter.api.extension.RegisterExtension
 import org.junit.jupiter.api.fail
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.ArgumentsSource
-import java.io.IOException
-import java.net.ServerSocket
-import java.net.Socket
-import java.util.concurrent.CountDownLatch
-import java.util.concurrent.TimeUnit.MILLISECONDS
-import javax.net.ServerSocketFactory
-import javax.net.SocketFactory
 
 @Timeout(30)
 @Tag("Slow")
@@ -85,7 +84,8 @@ class CancelTest {
   }
 
   @JvmField @RegisterExtension val clientTestRule = OkHttpClientTestRule()
-  val handshakeCertificates = TlsUtil.localhost()
+
+  val handshakeCertificates = platform.localhostHandshakeCertificates()
 
   private lateinit var server: MockWebServer
   private lateinit var client: OkHttpClient
@@ -100,8 +100,6 @@ class CancelTest {
       platform.assumeHttp2Support()
     }
 
-    platform.assumeNotBouncyCastle()
-
     // Sockets on some platforms can have large buffers that mean writes do not block when
     // required. These socket factories explicitly set the buffer sizes on sockets created.
     server = MockWebServer()
diff --git a/okhttp/src/jvmTest/java/okhttp3/internal/http2/HttpOverHttp2Test.kt b/okhttp/src/jvmTest/java/okhttp3/internal/http2/HttpOverHttp2Test.kt
index aab20ff93..2287ffd38 100644
--- a/okhttp/src/jvmTest/java/okhttp3/internal/http2/HttpOverHttp2Test.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/internal/http2/HttpOverHttp2Test.kt
@@ -70,7 +70,6 @@ import okhttp3.internal.discard
 import okhttp3.testing.Flaky
 import okhttp3.testing.PlatformRule
 import okhttp3.tls.HandshakeCertificates
-import okhttp3.tls.internal.TlsUtil.localhost
 import okio.Buffer
 import okio.BufferedSink
 import okio.GzipSink
@@ -109,6 +108,11 @@ class HttpOverHttp2Test {
   @RegisterExtension
   val testLogHandler: TestLogHandler = TestLogHandler(Http2::class.java)
 
+  // Flaky https://github.com/square/okhttp/issues/4632
+  // Flaky https://github.com/square/okhttp/issues/4633
+  private val handshakeCertificates: HandshakeCertificates =
+    platform.localhostHandshakeCertificates()
+
   private lateinit var server: MockWebServer
   private lateinit var protocol: Protocol
   private lateinit var client: OkHttpClient
@@ -125,7 +129,6 @@ class HttpOverHttp2Test {
     this.server = server
     this.protocol = protocol
     platform.assumeNotOpenJSSE()
-    platform.assumeNotBouncyCastle()
     if (protocol === Protocol.HTTP_2) {
       platform.assumeHttp2Support()
       server.useHttps(handshakeCertificates.sslSocketFactory())
@@ -2050,10 +2053,4 @@ class HttpOverHttp2Test {
     assertThat(get.requestLine).isEqualTo("GET /foo HTTP/1.1")
       assertThat(get.headers["Proxy-Authorization"]).isNull()
   }
-
-  companion object {
-    // Flaky https://github.com/square/okhttp/issues/4632
-    // Flaky https://github.com/square/okhttp/issues/4633
-    private val handshakeCertificates: HandshakeCertificates = localhost()
-  }
 }
diff --git a/okhttp/src/jvmTest/java/okhttp3/internal/tls/HostnameVerifierTest.kt b/okhttp/src/jvmTest/java/okhttp3/internal/tls/HostnameVerifierTest.kt
index 2a3c21e0d..84f16b38e 100644
--- a/okhttp/src/jvmTest/java/okhttp3/internal/tls/HostnameVerifierTest.kt
+++ b/okhttp/src/jvmTest/java/okhttp3/internal/tls/HostnameVerifierTest.kt
@@ -28,7 +28,6 @@ import okhttp3.internal.canParseAsIpAddress
 import okhttp3.internal.platform.Platform.Companion.isAndroid
 import okhttp3.testing.PlatformRule
 import okhttp3.tls.HeldCertificate
-import okhttp3.tls.internal.TlsUtil.localhost
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.extension.RegisterExtension
@@ -775,7 +774,8 @@ class HostnameVerifierTest {
 
     // Since this is public API, okhttp3.internal.tls.OkHostnameVerifier.verify is also
     assertThat(verifier).isInstanceOf(OkHostnameVerifier::class.java)
-    val session = localhost().sslContext().createSSLEngine().session
+    val handshakeCertificates = platform.localhostHandshakeCertificates()
+    val session = handshakeCertificates.sslContext().createSSLEngine().session
     assertThat(localVerifier.verify("\uD83D\uDCA9.com", session)).isFalse
   }
 
diff --git a/okhttp/src/jvmTest/java/okhttp3/internal/ws/WebSocketHttpTest.java b/okhttp/src/jvmTest/java/okhttp3/internal/ws/WebSocketHttpTest.java
index ab7811071..3646c6e31 100644
--- a/okhttp/src/jvmTest/java/okhttp3/internal/ws/WebSocketHttpTest.java
+++ b/okhttp/src/jvmTest/java/okhttp3/internal/ws/WebSocketHttpTest.java
@@ -57,7 +57,6 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import static java.util.Arrays.asList;
 import static okhttp3.TestUtil.repeat;
-import static okhttp3.tls.internal.TlsUtil.localhost;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.data.Offset.offset;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -73,7 +72,8 @@ public final class WebSocketHttpTest {
   @RegisterExtension TestLogHandler testLogHandler = new TestLogHandler(OkHttpClient.class);
 
   private MockWebServer webServer;
-  private final HandshakeCertificates handshakeCertificates = localhost();
+  private final HandshakeCertificates handshakeCertificates
+    = platform.localhostHandshakeCertificates();
   private final WebSocketRecorder clientListener = new WebSocketRecorder("client");
   private final WebSocketRecorder serverListener = new WebSocketRecorder("server");
   private final Random random = new Random(0);
@@ -98,7 +98,6 @@ public final class WebSocketHttpTest {
     this.webServer = webServer;
 
     platform.assumeNotOpenJSSE();
-    platform.assumeNotBouncyCastle();
   }
 
   @AfterEach public void tearDown() throws InterruptedException {
diff --git a/samples/compare/src/test/kotlin/okhttp3/compare/OkHttpClientTest.kt b/samples/compare/src/test/kotlin/okhttp3/compare/OkHttpClientTest.kt
index b1dd7587e..c3c66ad53 100644
--- a/samples/compare/src/test/kotlin/okhttp3/compare/OkHttpClientTest.kt
+++ b/samples/compare/src/test/kotlin/okhttp3/compare/OkHttpClientTest.kt
@@ -33,8 +33,6 @@ class OkHttpClientTest {
   @JvmField @RegisterExtension val platform = PlatformRule()
 
   @Test fun get(server: MockWebServer) {
-    platform.assumeNotBouncyCastle()
-
     server.enqueue(MockResponse(body = "hello, OkHttp"))
 
     val client = OkHttpClient()