[ECO-5380] Create separated unit test file for ObjectMessage

1. Added three different unit tests covering edge cases
2. Updated doc for byteSize String extension method

Author: sacOO7

live-objects/src/main/kotlin/io/ably/lib/objects/Utils.kt

@@ -37,6 +37,7 @@ internal fun serverError(errorMessage: String) = ablyException(errorMessage, Err
 /**
  * Calculates the byte size of a string.
  * For non-ASCII, the byte size can be 2–4x the character count. For ASCII, there is no difference.
+ * e.g. "Hello" has a byte size of 5, while "你" has a byte size of 3 and "😊" has a byte size of 4.
  */
 internal val String.byteSize: Int
   get() = this.toByteArray(Charsets.UTF_8).size

live-objects/src/test/kotlin/io/ably/lib/objects/unit/LiveObjectTest.kt

@@ -1,15 +1,7 @@
 package io.ably.lib.objects.unit
 
-import io.ably.lib.objects.*
-import io.ably.lib.objects.ObjectMessage
-import io.ably.lib.objects.size
-import io.ably.lib.types.AblyException
-import io.mockk.every
-import io.mockk.mockk
 import kotlinx.coroutines.test.runTest
 import org.junit.Test
-import kotlin.test.assertEquals
-import kotlin.test.assertFailsWith
 import kotlin.test.assertNotNull
 
 class LiveObjectTest {
@@ -19,34 +11,4 @@ class LiveObjectTest {
     val objects = channel.objects
     assertNotNull(objects)
   }
-
-  @Test
-  fun testObjectMessageSizeWithinLimit() = runTest {
-    val mockAdapter = mockk<LiveObjectsAdapter>()
-    every { mockAdapter.maxMessageSizeLimit() } returns 65536L // 64 kb
-    assertEquals(65536L, mockAdapter.maxMessageSizeLimit())
-
-    // Create ObjectMessage with dummy data that results in size 60 kb which is within the limit
-    val objectMessage = ObjectMessage(
-      clientId = CharArray(60 * 1024) { ('a'..'z').random() }.concatToString()
-    )
-    assertEquals(60 * 1024L, objectMessage.size()) // 60 kb (61,440 characters)
-    // Doesn't throw exception, so test doesn't fail
-    mockAdapter.ensureMessageSizeWithinLimit(arrayOf(objectMessage))
-
-    // Create ObjectMessage with dummy data that results in size 5kb
-    val objectMessage2 = ObjectMessage(
-      clientId = CharArray(5 * 1024) { ('a'..'z').random() }.concatToString()
-    )
-    assertEquals(5 * 1024L, objectMessage2.size()) // 5 kb
-
-    val exception = assertFailsWith<AblyException> {
-      // both messages together with size of 65kb exceed the limit
-      mockAdapter.ensureMessageSizeWithinLimit(arrayOf(objectMessage, objectMessage2))
-    }
-    // Assert on error code and message
-    assertEquals(40009, exception.errorInfo.code)
-    val expectedMessage = "ObjectMessage size 66560 exceeds maximum allowed size of 65536 bytes"
-    assertEquals(expectedMessage, exception.errorInfo.message)
-  }
 }

live-objects/src/test/kotlin/io/ably/lib/objects/unit/ObjectMessageSizeTest.kt

@@ -0,0 +1,73 @@
+package io.ably.lib.objects.unit
+
+import io.ably.lib.objects.*
+import io.ably.lib.objects.ObjectData
+import io.ably.lib.objects.ObjectMapOp
+import io.ably.lib.objects.ObjectMessage
+import io.ably.lib.objects.ObjectOperation
+import io.ably.lib.objects.ObjectOperationAction
+import io.ably.lib.objects.ObjectValue
+import io.ably.lib.objects.ensureMessageSizeWithinLimit
+import io.ably.lib.objects.size
+import io.ably.lib.types.AblyException
+import io.mockk.every
+import io.mockk.mockk
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+
+class ObjectMessageSizeTest {
+
+  @Test
+  fun testObjectMessageSizeWithinLimit() = runTest {
+    val mockAdapter = mockk<LiveObjectsAdapter>()
+    every { mockAdapter.maxMessageSizeLimit() } returns 65536L // 64 kb
+    assertEquals(65536L, mockAdapter.maxMessageSizeLimit())
+
+    // Create ObjectMessage with dummy data that results in size 60 kb which is within the limit
+    val objectMessage = ObjectMessage(
+      clientId = CharArray(60 * 1024) { ('a'..'z').random() }.concatToString()
+    )
+    assertEquals(60 * 1024L, objectMessage.size()) // 60 kb (61,440 characters)
+    // Doesn't throw exception, so test doesn't fail
+    mockAdapter.ensureMessageSizeWithinLimit(arrayOf(objectMessage))
+  }
+
+  @Test
+  fun testObjectMessageSizeForUnicodeCharacters() = runTest {
+    val objectMessage = ObjectMessage(
+      operation = ObjectOperation(
+        objectId = "",
+        action = ObjectOperationAction.MapCreate,
+        mapOp = ObjectMapOp(
+          key = "",
+          data = ObjectData(
+            value = ObjectValue("你😊") // 你 -> 3 bytes, 😊 -> 4 bytes
+          ),
+        ),
+      )
+    )
+    assertEquals(7, objectMessage.size())
+  }
+
+  @Test
+  fun testObjectMessageSizeAboveLimit() = runTest {
+    val mockAdapter = mockk<LiveObjectsAdapter>()
+    every { mockAdapter.maxMessageSizeLimit() } returns 65536L // 64 kb
+
+    // Create ObjectMessage with dummy data that results in size 65kb
+    val objectMessage = ObjectMessage(
+      clientId = CharArray(65 * 1024) { ('a'..'z').random() }.concatToString()
+    )
+    assertEquals(65 * 1024L, objectMessage.size())
+
+    val exception = assertFailsWith<AblyException> {
+      mockAdapter.ensureMessageSizeWithinLimit(arrayOf(objectMessage))
+    }
+    // Assert on error code and message
+    assertEquals(40009, exception.errorInfo.code)
+    val expectedMessage = "ObjectMessage size 66560 exceeds maximum allowed size of 65536 bytes"
+    assertEquals(expectedMessage, exception.errorInfo.message)
+  }
+}