diff --git a/test/functional/api/cas/cli_messages.py b/test/functional/api/cas/cli_messages.py
index 55fac85d8..2a4df97ef 100644
--- a/test/functional/api/cas/cli_messages.py
+++ b/test/functional/api/cas/cli_messages.py
@@ -7,7 +7,6 @@
 from core.test_run import TestRun
 from test_utils.output import Output
 
-
 load_inactive_core_missing = [
     r"WARNING: Can not resolve path to core \d+ from cache \d+\. By-id path will be shown for that "
     r"core\.",
@@ -70,6 +69,14 @@
     r"or try other device with the same logical sector size as core device\."
 ]
 
+partition_not_suitable_for_array = [
+    r"\S+ is not suitable for this array"
+]
+
+device_or_resource_busy = [
+    r"cannot open \S+: Device or resource busy"
+]
+
 
 def check_stderr_msg(output: Output, expected_messages):
     return __check_string_msg(output.stderr, expected_messages)
diff --git a/test/functional/tests/fault_injection/test_fault_injection_core_in_raid.py b/test/functional/tests/fault_injection/test_fault_injection_core_in_raid.py
new file mode 100644
index 000000000..253fb0823
--- /dev/null
+++ b/test/functional/tests/fault_injection/test_fault_injection_core_in_raid.py
@@ -0,0 +1,64 @@
+#
+# Copyright(c) 2021 Intel Corporation
+# SPDX-License-Identifier: BSD-3-Clause-Clear
+#
+import re
+
+import pytest
+
+from api.cas import casadm, cli_messages
+from api.cas.cache_config import CacheMode
+from core.test_run import TestRun
+from storage_devices.disk import DiskType, DiskTypeSet
+from storage_devices.raid import Raid, RaidConfiguration, MetadataVariant, Level
+from test_utils.size import Size, Unit
+
+
+@pytest.mark.parametrizex("cache_mode", CacheMode)
+@pytest.mark.require_disk("cache", DiskTypeSet([DiskType.optane, DiskType.nand]))
+@pytest.mark.require_disk("core", DiskTypeSet([DiskType.sata, DiskType.hdd]))
+def test_fault_injection_core_in_raid(cache_mode):
+    """
+        title: Test if OpenCAS rejects using core device to build SW RAID.
+        description: |
+          Test if OpenCAS handles properly attempting of use core device to build SW RAID.
+        pass_criteria:
+          - Expected to reject RAID creation with proper warning.
+    """
+    with TestRun.step("Prepare CAS device."):
+        cache_disk = TestRun.disks['cache']
+        core_disk = TestRun.disks['core']
+        cache_disk.create_partitions([Size(2, Unit.GibiByte)])
+        core_disk.create_partitions([Size(2, Unit.GibiByte)] * 2)
+        cache_dev = cache_disk.partitions[0]
+        core_dev = core_disk.partitions[0]
+        second_core_dev = core_disk.partitions[1]
+
+        cache = casadm.start_cache(cache_dev, cache_mode, force=True)
+        core = cache.add_core(core_dev)
+
+    with TestRun.step("Attempt to use core device to build SW RAID."):
+        raid_disk_1 = core_dev
+        raid_disk_2 = second_core_dev
+
+        expected_msg_1 = cli_messages.partition_not_suitable_for_array[0]
+        expected_msg_2 = cli_messages.device_or_resource_busy[0]
+
+        config = RaidConfiguration(
+            level=Level.Raid1,
+            metadata=MetadataVariant.Legacy,
+            number_of_devices=2)
+
+        try:
+            raid = Raid.create(config, [raid_disk_1, raid_disk_2])
+            TestRun.LOGGER.error(f"RAID created successfully. Expected otherwise.")
+        except Exception as ex:
+            output = ex.output
+
+    with TestRun.step("Looking for any of 2 expected messages."):
+        if re.search(expected_msg_1, output.stderr) or re.search(expected_msg_2, output.stderr):
+            TestRun.LOGGER.info("RAID not created. Found expected warning in exception message.")
+        else:
+            TestRun.LOGGER.error(f"RAID not created but warning message not as expected.\n"
+                                 f"Actual: '{output}'.\n"
+                                 f"Expected: '{expected_msg_1}' or '{expected_msg_2}'.")