#744 Add a unit test for the fixed record length extractor with recor…

…d length mapping with default record length.

cobol-parser/src/test/scala/za/co/absa/cobrix/cobol/reader/iterator/VRLRecordReaderSpec.scala

@@ -225,6 +225,58 @@ class VRLRecordReaderSpec extends AnyWordSpec {
 
         assert(ex.getMessage == "The record length field LEN must be an integral type or a value mapping must be specified.")
       }
+
+      "the length mapping with default record length" in {
+        val copybookWithLenbgthMap =
+          """       01  RECORD.
+            05  LEN_SPEC     PIC X(1).
+            05  N            PIC 9(2).
+            05  A            PIC X(3).
+          """
+
+        val records = Array(
+          0xC1, 0xF1, 0xF2, 0xC1,
+          0xC2, 0xF3, 0xF4, 0xC2, 0xC3,
+          0xC3, 0xF5, 0xF6, 0xC4, 0xC5, 0xC6
+        ).map(_.toByte)
+
+        val streamH = new ByteStreamMock(records)
+        val streamD = new ByteStreamMock(records)
+        val context = RawRecordContext(0, streamH, streamD, CopybookParser.parseSimple(copybookWithLenbgthMap), null, null, "")
+
+        val readerParameters = ReaderParameters(
+          lengthFieldExpression = Some("LEN_SPEC"),
+          lengthFieldMap = Map("A" -> 4, "B" -> 5, "_" -> 6))
+
+        val reader = getUseCase(
+          copybook = copybookWithLenbgthMap,
+          records = records,
+          lengthFieldExpression = Some("LEN_SPEC"),
+          recordExtractor = Some(new FixedWithRecordLengthExprRawRecordExtractor(context, readerParameters)))
+
+        assert(reader.hasNext)
+        val (segment1, record1) = reader.next()
+        assert(reader.hasNext)
+        val (segment2, record2) = reader.next()
+        assert(reader.hasNext)
+        val (segment3, record3) = reader.next()
+        assert(!reader.hasNext)
+
+        assert(segment1.isEmpty)
+        assert(segment2.isEmpty)
+        assert(segment3.isEmpty)
+        assert(record1.length == 4)
+        assert(record2.length == 5)
+        assert(record3.length == 6)
+        assert(record1(0) == 0xC1.toByte)
+        assert(record1(1) == 0xF1.toByte)
+        assert(record1(2) == 0xF2.toByte)
+        assert(record1(3) == 0xC1.toByte)
+        assert(record2(0) == 0xC2.toByte)
+        assert(record2(1) == 0xF3.toByte)
+        assert(record3(0) == 0xC3.toByte)
+        assert(record3(1) == 0xF5.toByte)
+      }
     }
 
     "work with record length expressions" in {