diff --git a/src/test/scala/com/exasol/cloudetl/it/BaseDataImporter.scala b/src/test/scala/com/exasol/cloudetl/it/BaseDataImporter.scala
index 94b4163c..aa49ed89 100644
--- a/src/test/scala/com/exasol/cloudetl/it/BaseDataImporter.scala
+++ b/src/test/scala/com/exasol/cloudetl/it/BaseDataImporter.scala
@@ -70,5 +70,21 @@ trait BaseDataImporter extends BaseS3IntegrationTest with BeforeAndAfterEach wit
       withResultSet(assertThat(_, matcher))
       ()
     }
+
+    def assertFails(errorMessageMatcher: Matcher[String]): Unit = {
+      paths.foreach(path => uploadFileToS3(bucketName, path))
+      val tableBuilder = schema
+        .createTableBuilder(tableName.toUpperCase(java.util.Locale.ENGLISH))
+      columns.foreach { case (colName, colType) =>
+        tableBuilder.column(colName, colType)
+      }
+
+      val table = tableBuilder.build()
+      val exception = intercept[IllegalStateException] {
+        importFromS3IntoExasol(schemaName, table, bucketName, s"$baseFileName*", dataFormat)
+      }
+      assertThat(exception.getCause().getMessage(), errorMessageMatcher)
+      ()
+    }
   }
 }
diff --git a/src/test/scala/com/exasol/cloudetl/it/BaseIntegrationTest.scala b/src/test/scala/com/exasol/cloudetl/it/BaseIntegrationTest.scala
index 5163de97..b4df9ac7 100644
--- a/src/test/scala/com/exasol/cloudetl/it/BaseIntegrationTest.scala
+++ b/src/test/scala/com/exasol/cloudetl/it/BaseIntegrationTest.scala
@@ -53,7 +53,7 @@ trait BaseIntegrationTest extends AnyFunSuite with BeforeAndAfterAll with LazyLo
       getConnection().createStatement().execute(sql)
     } catch {
       case exception: Exception =>
-        throw new AssertionError(s"Failed executing SQL '$sql': ${exception.getMessage()}", exception)
+        throw new IllegalStateException(s"Failed executing SQL '$sql': ${exception.getMessage()}", exception)
     }
     ()
   }
diff --git a/src/test/scala/com/exasol/cloudetl/it/parquet/ParquetDataImporterIT.scala b/src/test/scala/com/exasol/cloudetl/it/parquet/ParquetDataImporterIT.scala
index 5aa892b3..61341cde 100644
--- a/src/test/scala/com/exasol/cloudetl/it/parquet/ParquetDataImporterIT.scala
+++ b/src/test/scala/com/exasol/cloudetl/it/parquet/ParquetDataImporterIT.scala
@@ -19,6 +19,7 @@ import org.apache.parquet.example.data.simple.SimpleGroup
 import org.apache.parquet.hadoop.ParquetWriter
 import org.apache.parquet.io.api.Binary
 import org.apache.parquet.schema._
+import org.hamcrest.Matchers
 
 class ParquetDataImporterIT extends BaseDataImporter {
 
@@ -494,6 +495,73 @@ class ParquetDataImporterIT extends BaseDataImporter {
       )
   }
 
+  test("imports from multiple files") {
+    MultiParquetChecker(
+      "required binary name (UTF8); required int32 age;",
+      Map("NAME" -> "VARCHAR(60)", "AGE" -> "INTEGER"),
+      "multi_col"
+    )
+      .addParquetFile { case (writer, schema) =>
+        writer.write(new SimpleGroup(schema).append("name", "John").append("age", 24))
+      }
+      .addParquetFile { case (writer, schema) =>
+        writer.write(new SimpleGroup(schema).append("name", "Jane").append("age", 22))
+      }
+      .assertResultSet(
+        table("VARCHAR", "BIGINT")
+          .row("John", 24L)
+          .row("Jane", 22L)
+          .matches()
+      )
+  }
+
+  test("imports from file with missing field") {
+    MultiParquetChecker(
+      "required binary name (UTF8); required int32 age;",
+      Map("NAME" -> "VARCHAR(60)", "AGE" -> "INTEGER"),
+      "multi_col"
+    )
+      .addParquetFile { case (writer, schema) =>
+        writer.write(new SimpleGroup(schema).append("name", "John"))
+      }
+      .addParquetFile { case (writer, schema) =>
+        writer.write(new SimpleGroup(schema).append("name", "Jane").append("age", 22))
+      }
+      .assertResultSet(
+        table("VARCHAR", "BIGINT")
+          .row("John", null)
+          .row("Jane", 22L)
+          .matches()
+      )
+  }
+
+  test("importing from files with different schema fails") {
+    MultiParquetChecker(
+      "required binary name (UTF8);",
+      Map("NAME" -> "VARCHAR(60)", "AGE" -> "INTEGER"),
+      "multi_col"
+    )
+      .addParquetFileWithSchema(
+        MessageTypeParser.parseMessageType("message test { required binary name (UTF8); required int32 age; }"),
+        { case (writer, schema) =>
+          writer.write(new SimpleGroup(schema).append("name", "John").append("age", 24))
+        }
+      )
+      .addParquetFileWithSchema(
+        MessageTypeParser.parseMessageType("message test { required binary name (UTF8); }"),
+        { case (writer, schema) =>
+          writer.write(
+            new SimpleGroup(schema).append("name", "Jane")
+          )
+        }
+      )
+      .assertFails(
+        Matchers.containsString(
+          "ExaIterationException: E-UDF-CL-SL-JAVA-1107: emit() takes exactly 2 arguments (1 given)"
+        )
+      )
+  }
+
   case class ParquetChecker(parquetColumn: String, exaColumn: String, tableName: String)
       extends AbstractChecker(exaColumn, tableName)
       with ParquetTestDataWriter {
@@ -519,10 +587,16 @@ class ParquetDataImporterIT extends BaseDataImporter {
       with ParquetTestDataWriter {
     private val parquetSchema = MessageTypeParser.parseMessageType(s"message test { $parquetColumn }")
 
-    def addParquetFile(block: (ParquetWriter[Group], MessageType) => Unit): MultiParquetChecker = {
+    def addParquetFile(block: (ParquetWriter[Group], MessageType) => Unit): MultiParquetChecker =
+      addParquetFileWithSchema(parquetSchema, block)
+
+    def addParquetFileWithSchema(
+      customParquetSchema: MessageType,
+      block: (ParquetWriter[Group], MessageType) => Unit
+    ): MultiParquetChecker = {
       val path = addFile()
-      val writer = getParquetWriter(path, parquetSchema, true)
-      block(writer, parquetSchema)
+      val writer = getParquetWriter(path, customParquetSchema, true)
+      block(writer, customParquetSchema)
       writer.close()
       this
     }