Implement multipart tests

src/test/kotlin/backup/BackupClientTest.kt

@@ -6,6 +6,7 @@ import org.junit.jupiter.api.*
 import org.junit.jupiter.api.Assertions.*
 import java.io.File
 import kotlin.io.path.*
+import kotlin.random.Random
 
 val bucketName = System.getenv("BACKUP_BUCKET") ?: "teamcity-executors-test-task"
 
@@ -17,7 +18,7 @@ class BackupClientTest {
     fun `before each`() =
         runBlocking {
             s3 = S3Client.fromEnvironment {}
-            backupClient = BackupClient(s3, bucketName)
+            backupClient = BackupClient(s3, bucketName, 1024 * 1024 * 10)
         }
 
     @AfterEach
@@ -49,6 +50,26 @@ class BackupClientTest {
                     Path("_test/README.md").apply { writeText("# This is a test directory structure.") },
                 )
             },
+            "single large file" to {
+                val bytes = ByteArray(1024 * 1024 * 32)
+                Random.nextBytes(bytes)
+                listOf(
+                    Path("_test.txt").apply { writeBytes(bytes) }
+                )
+            },
+            "large directory structure" to {
+                val bytes1 = ByteArray(1024 * 1024 * 32)
+                val bytes2 = ByteArray(1024 * 1024 * 48)
+                listOf(
+                    Path("_test").createDirectory(),
+                    Path("_test/a.txt").apply { writeBytes(bytes1) },
+                    Path("_test/folder").createDirectory(),
+                    Path("_test/another-folder").createDirectory(),
+                    Path("_test/another-folder/b").apply { writeText("This is file B\n") },
+                    Path("_test/another-folder/c.txt").createFile(),
+                    Path("_test/README.md").apply { writeBytes(bytes2) },
+                )
+            }
         ).map { (name, pathsGen) ->
             DynamicTest.dynamicTest(name) {
                 val paths = pathsGen()