[Junie]: feat: make client property in ApplicationTestBuilder mutable

ktor-server/ktor-server-test-host/api/ktor-server-test-host.api

@@ -2,6 +2,7 @@ public final class io/ktor/server/testing/ApplicationTestBuilder : io/ktor/serve
 	public fun <init> ()V
 	public fun createClient (Lkotlin/jvm/functions/Function1;)Lio/ktor/client/HttpClient;
 	public fun getClient ()Lio/ktor/client/HttpClient;
+	public fun setClient (Lio/ktor/client/HttpClient;)V
 	public final fun startApplication (Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 }
 

ktor-server/ktor-server-test-host/api/ktor-server-test-host.klib.api

@@ -47,8 +47,9 @@ final class io.ktor.server.testing.client/TestHttpClientEngine : io.ktor.client.
 final class io.ktor.server.testing/ApplicationTestBuilder : io.ktor.server.testing/ClientProvider, io.ktor.server.testing/TestApplicationBuilder { // io.ktor.server.testing/ApplicationTestBuilder|null[0]
     constructor <init>() // io.ktor.server.testing/ApplicationTestBuilder.<init>|<init>(){}[0]
 
-    final val client // io.ktor.server.testing/ApplicationTestBuilder.client|{}client[0]
+    final var client // io.ktor.server.testing/ApplicationTestBuilder.client|{}client[0]
         final fun <get-client>(): io.ktor.client/HttpClient // io.ktor.server.testing/ApplicationTestBuilder.client.<get-client>|<get-client>(){}[0]
+        final fun <set-client>(io.ktor.client/HttpClient) // io.ktor.server.testing/ApplicationTestBuilder.client.<set-client>|<set-client>(io.ktor.client.HttpClient){}[0]
 
     final fun createClient(kotlin/Function1<io.ktor.client/HttpClientConfig<out io.ktor.client.engine/HttpClientEngineConfig>, kotlin/Unit>): io.ktor.client/HttpClient // io.ktor.server.testing/ApplicationTestBuilder.createClient|createClient(kotlin.Function1<io.ktor.client.HttpClientConfig<out|io.ktor.client.engine.HttpClientEngineConfig>,kotlin.Unit>){}[0]
     final suspend fun startApplication() // io.ktor.server.testing/ApplicationTestBuilder.startApplication|startApplication(){}[0]

ktor-server/ktor-server-test-host/common/src/io/ktor/server/testing/TestApplication.kt

@@ -30,7 +30,7 @@ import kotlin.coroutines.EmptyCoroutineContext
 @KtorDsl
 public interface ClientProvider {
     /**
-     * Returns a client with the default configuration.
+     * Returns the current client attached to the test application instance.
      *
      * [Report a problem](https://ktor.io/feedback/?fqname=io.ktor.server.testing.ClientProvider.client)
      *
@@ -373,7 +373,17 @@ public open class TestApplicationBuilder {
 @KtorDsl
 public class ApplicationTestBuilder : TestApplicationBuilder(), ClientProvider {
 
-    override val client: HttpClient by lazy { createClient { } }
+    private var _client: HttpClient? = null
+    override var client: HttpClient
+        get() {
+            if (_client == null) {
+                _client = createClient { }
+            }
+            return _client!!
+        }
+        set(value) {
+            _client = value
+        }
 
     internal val application: TestApplication by lazy {
         TestApplication(

ktor-server/ktor-server-test-host/common/test/TestApplicationTest.kt

@@ -267,6 +267,26 @@ class TestApplicationTest {
         assertEquals("OK", client.get("/").bodyAsText())
     }
 
+    @Test
+    fun testClientConfiguration() = testApplication {
+        application {
+            routing {
+                get("/hello") {
+                    call.respondText("Hello, World!")
+                }
+            }
+        }
+
+        val originalClient = client
+        client = createClient { }
+
+        assertNotSame(originalClient, client, "Client should be changed")
+
+        val response = client.get("/hello")
+        assertEquals(HttpStatusCode.OK, response.status)
+        assertEquals("Hello, World!", response.bodyAsText())
+    }
+
     @Test
     fun testMultipleParallelRequests() = testApplication {
         routing {