diff --git a/conformance/google-java/src/test/kotlin/com/connectrpc/conformance/Conformance.kt b/conformance/google-java/src/test/kotlin/com/connectrpc/conformance/Conformance.kt
index d5340c6b..f88c7be6 100644
--- a/conformance/google-java/src/test/kotlin/com/connectrpc/conformance/Conformance.kt
+++ b/conformance/google-java/src/test/kotlin/com/connectrpc/conformance/Conformance.kt
@@ -34,6 +34,7 @@ import com.connectrpc.okhttp.ConnectOkHttpClient
 import com.connectrpc.protocols.NetworkProtocol
 import com.google.protobuf.ByteString
 import com.google.protobuf.Empty
+import com.google.protobuf.empty
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.async
 import kotlinx.coroutines.runBlocking
@@ -528,6 +529,179 @@ class Conformance(
         }
     }
 
+    @Test
+    fun emptyUnaryCallback(): Unit = runBlocking {
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.emptyCall(empty {}) { response ->
+            response.failure {
+                fail<Unit>("expected error to be null")
+            }
+            response.success { success ->
+                assertThat(success.message).isEqualTo(empty {})
+                countDownLatch.countDown()
+            }
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun largeUnaryCallback(): Unit = runBlocking {
+        val size = 314159
+        val message = simpleRequest {
+            responseSize = size
+            payload = payload {
+                body = ByteString.copyFrom(ByteArray(size))
+            }
+        }
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.unaryCall(message) { response ->
+            response.failure {
+                fail<Unit>("expected error to be null")
+            }
+            response.success { success ->
+                assertThat(success.message.payload?.body?.toByteArray()?.size).isEqualTo(size)
+                countDownLatch.countDown()
+            }
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun customMetadataCallback(): Unit = runBlocking {
+        val size = 314159
+        val leadingKey = "x-grpc-test-echo-initial"
+        val leadingValue = "test_initial_metadata_value"
+        val trailingKey = "x-grpc-test-echo-trailing-bin"
+        val trailingValue = byteArrayOf(0xab.toByte(), 0xab.toByte(), 0xab.toByte())
+        val headers =
+            mapOf(
+                leadingKey to listOf(leadingValue),
+                trailingKey to listOf(b64Encode(trailingValue))
+            )
+        val message = simpleRequest {
+            responseSize = size
+            payload = payload { body = ByteString.copyFrom(ByteArray(size)) }
+        }
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.unaryCall(message, headers) { response ->
+            assertThat(response.code).isEqualTo(Code.OK)
+            assertThat(response.headers[leadingKey]).containsExactly(leadingValue)
+            assertThat(response.trailers[trailingKey]).containsExactly(b64Encode(trailingValue))
+            response.failure {
+                fail<Unit>("expected error to be null")
+            }
+            response.success { success ->
+                assertThat(success.message.payload!!.body!!.size()).isEqualTo(size)
+                countDownLatch.countDown()
+            }
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun statusCodeAndMessageCallback(): Unit = runBlocking {
+        val message = simpleRequest {
+            responseStatus = echoStatus {
+                code = Code.UNKNOWN.value
+                message = "test status message"
+            }
+        }
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.unaryCall(message) { response ->
+            assertThat(response.code).isEqualTo(Code.UNKNOWN)
+            response.failure { errorResponse ->
+                assertThat(errorResponse.error).isNotNull()
+                assertThat(errorResponse.code).isEqualTo(Code.UNKNOWN)
+                assertThat(errorResponse.error.message).isEqualTo("test status message")
+                countDownLatch.countDown()
+            }
+            response.success {
+                fail<Unit>("unexpected success")
+            }
+        }
+
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun specialStatusCallback(): Unit = runBlocking {
+        val statusMessage =
+            "\\t\\ntest with whitespace\\r\\nand Unicode BMP ☺ and non-BMP \uD83D\uDE08\\t\\n"
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.unaryCall(
+            simpleRequest {
+                responseStatus = echoStatus {
+                    code = 2
+                    message = statusMessage
+                }
+            }
+        ) { response ->
+            response.failure { errorResponse ->
+                val error = errorResponse.error
+                assertThat(error.code).isEqualTo(Code.UNKNOWN)
+                assertThat(response.code).isEqualTo(Code.UNKNOWN)
+                assertThat(error.message).isEqualTo(statusMessage)
+                countDownLatch.countDown()
+            }
+            response.success {
+                fail<Unit>("unexpected success")
+            }
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun unimplementedMethodCallback(): Unit = runBlocking {
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.unimplementedCall(empty {}) { response ->
+            assertThat(response.code).isEqualTo(Code.UNIMPLEMENTED)
+            countDownLatch.countDown()
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun unimplementedServiceCallback(): Unit = runBlocking {
+        val countDownLatch = CountDownLatch(1)
+        unimplementedServiceClient.unimplementedCall(empty {}) { response ->
+            assertThat(response.code).isEqualTo(Code.UNIMPLEMENTED)
+            countDownLatch.countDown()
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
+    @Test
+    fun failUnaryCallback(): Unit = runBlocking {
+        val expectedErrorDetail = errorDetail {
+            reason = "soirée 🎉"
+            domain = "connect-conformance"
+        }
+        val countDownLatch = CountDownLatch(1)
+        testServiceConnectClient.failUnaryCall(simpleRequest {}) { response ->
+            assertThat(response.code).isEqualTo(Code.RESOURCE_EXHAUSTED)
+            response.failure { errorResponse ->
+                val error = errorResponse.error
+                assertThat(error.code).isEqualTo(Code.RESOURCE_EXHAUSTED)
+                assertThat(error.message).isEqualTo("soirée 🎉")
+                val connectErrorDetails = error.unpackedDetails(ErrorDetail::class)
+                assertThat(connectErrorDetails).containsExactly(expectedErrorDetail)
+                countDownLatch.countDown()
+            }
+            response.success {
+                fail<Unit>("unexpected success")
+            }
+        }
+        countDownLatch.await(500, TimeUnit.MILLISECONDS)
+        assertThat(countDownLatch.count).isZero()
+    }
+
     private fun b64Encode(trailingValue: ByteArray): String {
         return String(Base64.getEncoder().encode(trailingValue))
     }