diff --git a/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileBinaryTest.kt b/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileBinaryTest.kt
index d8c7c67a..8a31346a 100644
--- a/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileBinaryTest.kt
+++ b/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileBinaryTest.kt
@@ -4,6 +4,7 @@ import hep.dataforge.context.Global
 import java.nio.file.Files
 import kotlin.test.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertTrue
 
 class FileBinaryTest {
     val envelope = Envelope {
@@ -53,4 +54,30 @@ class FileBinaryTest {
         assertEquals(binary.size.toInt(), binary.toBytes().size)
     }
 
+    @Test
+    fun testMultyPartFileData() {
+        val envelopeList = (0..5).map {
+            val dataFile = Files.createTempFile("dataforge_test_bin_$it", ".bin")
+            dataFile.toFile().writeText(DoubleArray(80000) { it.toDouble() }.joinToString())
+            val envelopeFromFile = Envelope {
+                meta {
+                    "a" put "AAA"
+                    "b" put 22.2
+                }
+                dataType = "hep.dataforge.satellite"
+                dataID = "cellDepositTest$it" // добавил только что
+                data = dataFile.asBinary()
+            }
+            envelopeFromFile
+        }
+
+        val envelope = Envelope {
+            multipart(TaggedEnvelopeFormat, envelopeList)
+        }
+        println(envelopeList.map { it.data?.size }.joinToString(" "))
+        println(envelope.data?.size)
+        assertTrue { envelope.data!!.size > envelopeList.map { it.data!!.size }.sum() }
+
+    }
+
 }
\ No newline at end of file
diff --git a/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileEnvelopeTest.kt b/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileEnvelopeTest.kt
index 585aced9..f77e4903 100644
--- a/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileEnvelopeTest.kt
+++ b/dataforge-io/src/jvmTest/kotlin/hep/dataforge/io/FileEnvelopeTest.kt
@@ -1,9 +1,13 @@
 package hep.dataforge.io
 
 import hep.dataforge.context.Global
+import java.nio.ByteBuffer
 import java.nio.file.Files
+import java.util.*
 import kotlin.test.Test
+import kotlin.test.assertEquals
 import kotlin.test.assertTrue
+import kotlin.test.fail
 
 
 class FileEnvelopeTest {
@@ -31,14 +35,68 @@ class FileEnvelopeTest {
         }
     }
 
+    @Test
+    fun testFileWriteTagged() {
+        val tmpPath = Files.createTempFile("dataforge_test", ".df")
+        Global.io.writeEnvelopeFile(tmpPath, envelope)
+        assertTrue { tmpPath.toFile().length() > 0 }
+    }
+
+    @Test
+    fun testFileWriteReadTagged() {
+        val tmpPath = Files.createTempFile("dataforge_test", ".df")
+        Global.io.writeEnvelopeFile(tmpPath, envelope)
+        println(tmpPath.toUri())
+        val restored: Envelope = Global.io.readEnvelopeFile(tmpPath)!!
+        assertTrue { envelope.contentEquals(restored) }
+    }
+
+    @Test
+    fun testFileWriteTagless() {
+        val tmpPath = Files.createTempFile("dataforge_test", ".df")
+        Global.io.writeEnvelopeFile(tmpPath, envelope, envelopeFormat = TaglessEnvelopeFormat)
+        assertTrue { tmpPath.toFile().length() > 0 }
+    }
+
     @Test
     fun testFileWriteReadTagless() {
-        Global.io.run {
-            val tmpPath = Files.createTempFile("dataforge_test_tagless", ".df")
-            writeEnvelopeFile(tmpPath, envelope, envelopeFormat = TaglessEnvelopeFormat)
-            println(tmpPath.toUri())
-            val restored: Envelope = readEnvelopeFile(tmpPath)!!
-            assertTrue { envelope.contentEquals(restored) }
+        val tmpPath = Files.createTempFile("dataforge_test", ".df")
+        Global.io.writeEnvelopeFile(tmpPath, envelope, envelopeFormat = TaglessEnvelopeFormat)
+        println(tmpPath.toUri())
+        val restored: Envelope = Global.io.readEnvelopeFile(tmpPath)!!
+        assertTrue { envelope.contentEquals(restored) }
+    }
+
+    @Test
+    fun testDataSize() {
+        val tmpPath = Files.createTempFile("dataforge_test", ".df")
+        Global.io.writeEnvelopeFile(tmpPath, envelope)
+        println(tmpPath.toUri())
+        val scan = Scanner(tmpPath.toFile().inputStream()).useDelimiter("\n").nextLine()
+        println(scan)
+        val format = scan.slice(2..5)
+        when (format) {
+            "DF03" -> {
+                val buff = ByteBuffer.allocate(4)
+                buff.put(scan.slice(12..19).toByteArray())
+                buff.flip()
+                val size = buff.long
+                println(size)
+                assertEquals(8, size)
+            }
+            "DF02" -> {
+                val buff = ByteBuffer.allocate(4)
+                buff.put(scan.slice(12..15).toByteArray())
+                buff.flip()
+                val size = buff.int
+                println(size)
+                assertEquals(8, size)
+            }
+            else -> {
+                fail("Format $format don't have test")
+            }
         }
     }
+
+
 }
\ No newline at end of file