diff --git a/UNITTESTS/drivers/PwmOut/unittest.cmake b/UNITTESTS/drivers/PwmOut/unittest.cmake
index 475cf0ae94..84dc7938d2 100644
--- a/UNITTESTS/drivers/PwmOut/unittest.cmake
+++ b/UNITTESTS/drivers/PwmOut/unittest.cmake
@@ -19,7 +19,7 @@ set(unittest-sources
 set(unittest-test-sources
   drivers/PwmOut/test_pwmout.cpp
   stubs/mbed_critical_stub.c
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/pwmout_api_stub.c
 )
 
diff --git a/UNITTESTS/drivers/Watchdog/unittest.cmake b/UNITTESTS/drivers/Watchdog/unittest.cmake
index 1b907a9f54..702ef40ac7 100644
--- a/UNITTESTS/drivers/Watchdog/unittest.cmake
+++ b/UNITTESTS/drivers/Watchdog/unittest.cmake
@@ -19,7 +19,7 @@ set(unittest-sources
 set(unittest-test-sources
   drivers/Watchdog/test_watchdog.cpp  
   stubs/mbed_critical_stub.c  
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/watchdog_api_stub.c
 )
 
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellularbase/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellularbase/unittest.cmake
index beff24981a..a5eb81daab 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellularbase/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellularbase/unittest.cmake
@@ -21,7 +21,7 @@ set(unittest-sources
 # Test files
 set(unittest-test-sources
   features/cellular/framework/AT/at_cellularbase/at_cellularbasetest.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/ATHandler_stub.cpp
   stubs/EventQueue_stub.cpp
   stubs/FileHandle_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellularcontext/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellularcontext/unittest.cmake
index 15bcccf231..4f37b2e497 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellularcontext/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellularcontext/unittest.cmake
@@ -30,7 +30,7 @@ set(unittest-test-sources
   stubs/equeue_stub.c
   stubs/EventQueue_stub.cpp
   stubs/FileHandle_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/NetworkInterface_stub.cpp
   stubs/NetworkInterfaceDefaults_stub.cpp
   stubs/NetworkStack_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellulardevice/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellulardevice/unittest.cmake
index ac50a142f6..cc4bd08556 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellulardevice/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellulardevice/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   stubs/NetworkInterfaceDefaults_stub.cpp
   stubs/EventQueue_stub.cpp
   stubs/FileHandle_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/CellularDevice_stub.cpp
   stubs/NetworkStack_stub.cpp
   stubs/AT_CellularContext_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellularinformation/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellularinformation/unittest.cmake
index c8a646694f..f49beec89f 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellularinformation/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellularinformation/unittest.cmake
@@ -24,7 +24,7 @@ set(unittest-test-sources
   stubs/AT_CellularBase_stub.cpp
   stubs/EventQueue_stub.cpp
   stubs/FileHandle_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/ConditionVariable_stub.cpp
   stubs/Mutex_stub.cpp
 )
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellularnetwork/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellularnetwork/unittest.cmake
index d2e6330239..e68b7e6819 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellularnetwork/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellularnetwork/unittest.cmake
@@ -25,7 +25,7 @@ set(unittest-test-sources
   stubs/EventQueue_stub.cpp
   stubs/FileHandle_stub.cpp
   stubs/us_ticker_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/SocketAddress_stub.cpp
   stubs/randLIB_stub.cpp
   stubs/ConditionVariable_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellularsms/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellularsms/unittest.cmake
index c2407a6adf..0e2083992b 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellularsms/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellularsms/unittest.cmake
@@ -25,7 +25,7 @@ set(unittest-test-sources
   stubs/FileHandle_stub.cpp
   stubs/CellularUtil_stub.cpp
   stubs/us_ticker_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/ThisThread_stub.cpp
   stubs/mbed_wait_api_stub.cpp
   stubs/ConditionVariable_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/AT/at_cellularstack/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/at_cellularstack/unittest.cmake
index 85bd80fd5c..145dedb118 100644
--- a/UNITTESTS/features/cellular/framework/AT/at_cellularstack/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/at_cellularstack/unittest.cmake
@@ -27,7 +27,7 @@ set(unittest-test-sources
   stubs/us_ticker_stub.cpp
   stubs/NetworkStack_stub.cpp
   stubs/SocketAddress_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/ThisThread_stub.cpp
   stubs/ConditionVariable_stub.cpp
   stubs/Mutex_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/AT/athandler/unittest.cmake b/UNITTESTS/features/cellular/framework/AT/athandler/unittest.cmake
index 6d0419fed5..e47181168f 100644
--- a/UNITTESTS/features/cellular/framework/AT/athandler/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/AT/athandler/unittest.cmake
@@ -27,7 +27,7 @@ set(unittest-test-sources
   stubs/us_ticker_stub.cpp
   stubs/UARTSerial_stub.cpp
   stubs/SerialBase_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_poll_stub.cpp
   stubs/Timer_stub.cpp
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/cellular/framework/device/cellularcontext/unittest.cmake b/UNITTESTS/features/cellular/framework/device/cellularcontext/unittest.cmake
index fe3072e288..6b1757f2a0 100644
--- a/UNITTESTS/features/cellular/framework/device/cellularcontext/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/device/cellularcontext/unittest.cmake
@@ -22,7 +22,7 @@ set(unittest-test-sources
   stubs/FileHandle_stub.cpp
   stubs/CellularStateMachine_stub.cpp
   stubs/EventQueue_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/UARTSerial_stub.cpp
   stubs/SerialBase_stub.cpp
   stubs/ATHandler_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/device/cellulardevice/unittest.cmake b/UNITTESTS/features/cellular/framework/device/cellulardevice/unittest.cmake
index c6e4ae3767..4177b67cf6 100644
--- a/UNITTESTS/features/cellular/framework/device/cellulardevice/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/device/cellulardevice/unittest.cmake
@@ -22,7 +22,7 @@ set(unittest-test-sources
   stubs/FileHandle_stub.cpp
   stubs/CellularStateMachine_stub.cpp
   stubs/EventQueue_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/UARTSerial_stub.cpp
   stubs/SerialBase_stub.cpp
   stubs/ATHandler_stub.cpp
diff --git a/UNITTESTS/features/cellular/framework/device/cellularstatemachine/unittest.cmake b/UNITTESTS/features/cellular/framework/device/cellularstatemachine/unittest.cmake
index 172ba725d8..9b844877c1 100644
--- a/UNITTESTS/features/cellular/framework/device/cellularstatemachine/unittest.cmake
+++ b/UNITTESTS/features/cellular/framework/device/cellularstatemachine/unittest.cmake
@@ -22,7 +22,7 @@ set(unittest-test-sources
   stubs/FileHandle_stub.cpp
   stubs/CellularDevice_stub.cpp
   stubs/EventQueue_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/UARTSerial_stub.cpp
   stubs/SerialBase_stub.cpp
   stubs/ATHandler_stub.cpp
diff --git a/UNITTESTS/features/lorawan/loramac/unittest.cmake b/UNITTESTS/features/lorawan/loramac/unittest.cmake
index 24ba918272..bb999d8850 100644
--- a/UNITTESTS/features/lorawan/loramac/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loramac/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/loramac/Test_LoRaMac.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANStack_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/LoRaMacCrypto_stub.cpp
   stubs/LoRaMacChannelPlan_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
diff --git a/UNITTESTS/features/lorawan/loramaccommand/unittest.cmake b/UNITTESTS/features/lorawan/loramaccommand/unittest.cmake
index 1dc3272977..cd05c2c44a 100644
--- a/UNITTESTS/features/lorawan/loramaccommand/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loramaccommand/unittest.cmake
@@ -32,7 +32,7 @@ set(unittest-includes ${unittest-includes}
 # Test & stub files
 set(unittest-test-sources
   features/lorawan/loramaccommand/Test_LoRaMacCommand.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/LoRaPHY_stub.cpp
 )
 
diff --git a/UNITTESTS/features/lorawan/loramaccrypto/unittest.cmake b/UNITTESTS/features/lorawan/loramaccrypto/unittest.cmake
index 2001f8e9d7..69ab1c8ff7 100644
--- a/UNITTESTS/features/lorawan/loramaccrypto/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loramaccrypto/unittest.cmake
@@ -35,7 +35,7 @@ set(unittest-test-sources
   stubs/cipher_stub.c
   stubs/aes_stub.c
   stubs/cmac_stub.c
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   ../features/nanostack/coap-service/test/coap-service/unittest/stub/mbedtls_stub.c
 
 )
diff --git a/UNITTESTS/features/lorawan/loraphy/unittest.cmake b/UNITTESTS/features/lorawan/loraphy/unittest.cmake
index b3c8a5854a..7eef3259c1 100644
--- a/UNITTESTS/features/lorawan/loraphy/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphy/unittest.cmake
@@ -33,7 +33,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-test-sources
   features/lorawan/loraphy/Test_LoRaPHY.cpp
   stubs/LoRaWANTimer_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 )
 
 
diff --git a/UNITTESTS/features/lorawan/loraphyas923/unittest.cmake b/UNITTESTS/features/lorawan/loraphyas923/unittest.cmake
index b4648ab904..c54402ee5e 100644
--- a/UNITTESTS/features/lorawan/loraphyas923/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphyas923/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/loraphyas923/Test_LoRaPHYAS923.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphyau915/unittest.cmake b/UNITTESTS/features/lorawan/loraphyau915/unittest.cmake
index abc6c4752c..e225f5b324 100644
--- a/UNITTESTS/features/lorawan/loraphyau915/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphyau915/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/loraphyau915/Test_LoRaPHYAU915.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphycn470/unittest.cmake b/UNITTESTS/features/lorawan/loraphycn470/unittest.cmake
index 6c6746f189..f3e2caa64a 100644
--- a/UNITTESTS/features/lorawan/loraphycn470/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphycn470/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/loraphycn470/Test_LoRaPHYCN470.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphycn779/unittest.cmake b/UNITTESTS/features/lorawan/loraphycn779/unittest.cmake
index d0ccd7fece..aabf895989 100644
--- a/UNITTESTS/features/lorawan/loraphycn779/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphycn779/unittest.cmake
@@ -33,7 +33,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-test-sources
   features/lorawan/loraphycn779/Test_LoRaPHYCN779.cpp
   stubs/LoRaPHY_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphyeu433/unittest.cmake b/UNITTESTS/features/lorawan/loraphyeu433/unittest.cmake
index 5966a3ee60..b4544ed8aa 100644
--- a/UNITTESTS/features/lorawan/loraphyeu433/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphyeu433/unittest.cmake
@@ -33,7 +33,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-test-sources
   features/lorawan/loraphyeu433/Test_LoRaPHYEU433.cpp
   stubs/LoRaPHY_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphyeu868/unittest.cmake b/UNITTESTS/features/lorawan/loraphyeu868/unittest.cmake
index 1398a52257..14887b49a3 100644
--- a/UNITTESTS/features/lorawan/loraphyeu868/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphyeu868/unittest.cmake
@@ -33,7 +33,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-test-sources
   features/lorawan/loraphyeu868/Test_LoRaPHYEU868.cpp
   stubs/LoRaPHY_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphyin865/unittest.cmake b/UNITTESTS/features/lorawan/loraphyin865/unittest.cmake
index 2fa34a6f73..74231bf9a9 100644
--- a/UNITTESTS/features/lorawan/loraphyin865/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphyin865/unittest.cmake
@@ -33,7 +33,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-test-sources
   features/lorawan/loraphyin865/Test_LoRaPHYIN865.cpp
   stubs/LoRaPHY_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphykr920/unittest.cmake b/UNITTESTS/features/lorawan/loraphykr920/unittest.cmake
index cc32c13f02..ee92a1472e 100644
--- a/UNITTESTS/features/lorawan/loraphykr920/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphykr920/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/loraphykr920/Test_LoRaPHYKR920.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/loraphyus915/unittest.cmake b/UNITTESTS/features/lorawan/loraphyus915/unittest.cmake
index f181da5e3f..5e7ac3305d 100644
--- a/UNITTESTS/features/lorawan/loraphyus915/unittest.cmake
+++ b/UNITTESTS/features/lorawan/loraphyus915/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/loraphyus915/Test_LoRaPHYUS915.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 
 )
 
diff --git a/UNITTESTS/features/lorawan/lorawaninterface/unittest.cmake b/UNITTESTS/features/lorawan/lorawaninterface/unittest.cmake
index f99ccca9ba..ce3ff46233 100644
--- a/UNITTESTS/features/lorawan/lorawaninterface/unittest.cmake
+++ b/UNITTESTS/features/lorawan/lorawaninterface/unittest.cmake
@@ -35,7 +35,7 @@ set(unittest-test-sources
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaWANStack_stub.cpp
   stubs/LoRaMac_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/LoRaMacCrypto_stub.cpp
   stubs/LoRaMacChannelPlan_stub.cpp
   stubs/LoRaWANTimer_stub.cpp
diff --git a/UNITTESTS/features/lorawan/lorawanstack/unittest.cmake b/UNITTESTS/features/lorawan/lorawanstack/unittest.cmake
index b8b506c044..8cb8d6af5f 100644
--- a/UNITTESTS/features/lorawan/lorawanstack/unittest.cmake
+++ b/UNITTESTS/features/lorawan/lorawanstack/unittest.cmake
@@ -34,7 +34,7 @@ set(unittest-test-sources
   features/lorawan/lorawanstack/Test_LoRaWANStack.cpp
   stubs/LoRaPHY_stub.cpp
   stubs/LoRaMac_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/LoRaMacCrypto_stub.cpp
   stubs/LoRaMacChannelPlan_stub.cpp
diff --git a/UNITTESTS/features/lorawan/lorawantimer/unittest.cmake b/UNITTESTS/features/lorawan/lorawantimer/unittest.cmake
index 75dd100985..663f4ba674 100644
--- a/UNITTESTS/features/lorawan/lorawantimer/unittest.cmake
+++ b/UNITTESTS/features/lorawan/lorawantimer/unittest.cmake
@@ -33,7 +33,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-test-sources
   features/lorawan/lorawantimer/Test_LoRaWANTimer.cpp
   stubs/EventQueue_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/equeue_stub.c
 )
 
diff --git a/UNITTESTS/features/netsocket/DTLSSocket/unittest.cmake b/UNITTESTS/features/netsocket/DTLSSocket/unittest.cmake
index fa43a292ee..29f7916c8a 100644
--- a/UNITTESTS/features/netsocket/DTLSSocket/unittest.cmake
+++ b/UNITTESTS/features/netsocket/DTLSSocket/unittest.cmake
@@ -22,7 +22,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/DTLSSocket/test_DTLSSocket.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/DTLSSocketWrapper/unittest.cmake b/UNITTESTS/features/netsocket/DTLSSocketWrapper/unittest.cmake
index 98f011a071..ddf449e3fb 100644
--- a/UNITTESTS/features/netsocket/DTLSSocketWrapper/unittest.cmake
+++ b/UNITTESTS/features/netsocket/DTLSSocketWrapper/unittest.cmake
@@ -21,7 +21,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/DTLSSocketWrapper/test_DTLSSocketWrapper.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/EthernetInterface/unittest.cmake b/UNITTESTS/features/netsocket/EthernetInterface/unittest.cmake
index d0dfbdf151..7b9dba8511 100644
--- a/UNITTESTS/features/netsocket/EthernetInterface/unittest.cmake
+++ b/UNITTESTS/features/netsocket/EthernetInterface/unittest.cmake
@@ -25,7 +25,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/EthernetInterface/test_EthernetInterface.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/equeue_stub.c
   stubs/EventQueue_stub.cpp
   stubs/mbed_shared_queues_stub.cpp
diff --git a/UNITTESTS/features/netsocket/InternetSocket/unittest.cmake b/UNITTESTS/features/netsocket/InternetSocket/unittest.cmake
index 39575a6a10..a6793bf24f 100644
--- a/UNITTESTS/features/netsocket/InternetSocket/unittest.cmake
+++ b/UNITTESTS/features/netsocket/InternetSocket/unittest.cmake
@@ -17,7 +17,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/InternetSocket/test_InternetSocket.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/NetworkInterface/unittest.cmake b/UNITTESTS/features/netsocket/NetworkInterface/unittest.cmake
index 5c142078da..2d2888f193 100644
--- a/UNITTESTS/features/netsocket/NetworkInterface/unittest.cmake
+++ b/UNITTESTS/features/netsocket/NetworkInterface/unittest.cmake
@@ -19,7 +19,7 @@ set(unittest-sources
 # Test files
 set(unittest-test-sources
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/equeue_stub.c
   stubs/EventQueue_stub.cpp
   stubs/mbed_shared_queues_stub.cpp
diff --git a/UNITTESTS/features/netsocket/NetworkStack/unittest.cmake b/UNITTESTS/features/netsocket/NetworkStack/unittest.cmake
index 6daf74304e..ec4f1d91be 100644
--- a/UNITTESTS/features/netsocket/NetworkStack/unittest.cmake
+++ b/UNITTESTS/features/netsocket/NetworkStack/unittest.cmake
@@ -21,7 +21,7 @@ set(unittest-sources
 # Test files
 set(unittest-test-sources
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/equeue_stub.c
   stubs/EventQueue_stub.cpp
   stubs/mbed_error.c
diff --git a/UNITTESTS/features/netsocket/TCPServer/unittest.cmake b/UNITTESTS/features/netsocket/TCPServer/unittest.cmake
index e8c4572bad..482b8ae061 100644
--- a/UNITTESTS/features/netsocket/TCPServer/unittest.cmake
+++ b/UNITTESTS/features/netsocket/TCPServer/unittest.cmake
@@ -21,7 +21,7 @@ set(unittest-sources
 
 set(unittest-test-sources
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/TCPSocket/unittest.cmake b/UNITTESTS/features/netsocket/TCPSocket/unittest.cmake
index f21779b405..92b506ba72 100644
--- a/UNITTESTS/features/netsocket/TCPSocket/unittest.cmake
+++ b/UNITTESTS/features/netsocket/TCPSocket/unittest.cmake
@@ -18,7 +18,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/TCPSocket/test_TCPSocket.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/TLSSocket/unittest.cmake b/UNITTESTS/features/netsocket/TLSSocket/unittest.cmake
index 9e0b906fe8..e4746d3df4 100644
--- a/UNITTESTS/features/netsocket/TLSSocket/unittest.cmake
+++ b/UNITTESTS/features/netsocket/TLSSocket/unittest.cmake
@@ -20,7 +20,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/TLSSocket/test_TLSSocket.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/TLSSocketWrapper/unittest.cmake b/UNITTESTS/features/netsocket/TLSSocketWrapper/unittest.cmake
index d126328baf..2096f1da75 100644
--- a/UNITTESTS/features/netsocket/TLSSocketWrapper/unittest.cmake
+++ b/UNITTESTS/features/netsocket/TLSSocketWrapper/unittest.cmake
@@ -19,7 +19,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/TLSSocketWrapper/test_TLSSocketWrapper.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/UDPSocket/unittest.cmake b/UNITTESTS/features/netsocket/UDPSocket/unittest.cmake
index b23122f4b3..3eabef520d 100644
--- a/UNITTESTS/features/netsocket/UDPSocket/unittest.cmake
+++ b/UNITTESTS/features/netsocket/UDPSocket/unittest.cmake
@@ -19,7 +19,7 @@ set(unittest-sources
 set(unittest-test-sources
   features/netsocket/UDPSocket/test_UDPSocket.cpp
   stubs/Mutex_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_atomic_stub.c
   stubs/mbed_critical_stub.c
   stubs/equeue_stub.c
diff --git a/UNITTESTS/features/netsocket/cellular/CellularNonIPSocket/unittest.cmake b/UNITTESTS/features/netsocket/cellular/CellularNonIPSocket/unittest.cmake
index 57ace7017d..05e1710710 100644
--- a/UNITTESTS/features/netsocket/cellular/CellularNonIPSocket/unittest.cmake
+++ b/UNITTESTS/features/netsocket/cellular/CellularNonIPSocket/unittest.cmake
@@ -20,5 +20,5 @@ set(unittest-test-sources
   stubs/EventFlags_stub.cpp
   stubs/Mutex_stub.cpp
   stubs/CellularContext_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 )
diff --git a/UNITTESTS/features/netsocket/nsapi_dns/unittest.cmake b/UNITTESTS/features/netsocket/nsapi_dns/unittest.cmake
index 331945f83c..ba983cb6f7 100644
--- a/UNITTESTS/features/netsocket/nsapi_dns/unittest.cmake
+++ b/UNITTESTS/features/netsocket/nsapi_dns/unittest.cmake
@@ -21,7 +21,7 @@ set(unittest-sources
 set(unittest-test-sources
   stubs/Mutex_stub.cpp
   ../features/netsocket/SocketAddress.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/NetworkStack_stub.cpp
   stubs/NetworkInterfaceDefaults_stub.cpp
   stubs/mbed_atomic_stub.c
diff --git a/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/test.cpp b/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/test.cpp
index 659b47b462..c7bf7dfcba 100644
--- a/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/test.cpp
+++ b/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/test.cpp
@@ -50,6 +50,12 @@ TEST_F(HeapBlockDeviceTest, constructor)
     EXPECT_EQ(one.deinit(), BD_ERROR_OK);
 }
 
+TEST_F(HeapBlockDeviceTest, constructor_wrong_size)
+{
+    mbed_assert_throw_errors=true;
+    ASSERT_ANY_THROW(mbed::HeapBlockDevice one(3050, 100));
+}
+
 TEST_F(HeapBlockDeviceTest, double_init)
 {
     mbed::HeapBlockDevice one{DEVICE_SIZE};
diff --git a/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/unittest.cmake b/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/unittest.cmake
index 8ae0f85c9d..0c064dc8f5 100644
--- a/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/unittest.cmake
+++ b/UNITTESTS/features/storage/blockdevice/HeapBlockDevice/unittest.cmake
@@ -11,7 +11,7 @@ set(unittest-includes ${unittest-includes}
 set(unittest-sources
   ../features/storage/blockdevice/HeapBlockDevice.cpp
   stubs/mbed_atomic_stub.c
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 )
 
 set(unittest-test-sources
diff --git a/UNITTESTS/moduletests/storage/blockdevice/SlicingBlockDevice/unittest.cmake b/UNITTESTS/moduletests/storage/blockdevice/SlicingBlockDevice/unittest.cmake
index 93285d0a13..83d0e0d7e6 100644
--- a/UNITTESTS/moduletests/storage/blockdevice/SlicingBlockDevice/unittest.cmake
+++ b/UNITTESTS/moduletests/storage/blockdevice/SlicingBlockDevice/unittest.cmake
@@ -12,7 +12,7 @@ set(unittest-sources
   ../features/storage/blockdevice/SlicingBlockDevice.cpp
   ../features/storage/blockdevice/HeapBlockDevice.cpp
   stubs/mbed_atomic_stub.c
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
 )
 
 set(unittest-test-sources
diff --git a/UNITTESTS/platform/ATCmdParser/unittest.cmake b/UNITTESTS/platform/ATCmdParser/unittest.cmake
index 29daa2bdea..de19302015 100644
--- a/UNITTESTS/platform/ATCmdParser/unittest.cmake
+++ b/UNITTESTS/platform/ATCmdParser/unittest.cmake
@@ -11,6 +11,6 @@ set(unittest-sources
 set(unittest-test-sources
   platform/ATCmdParser/test_ATCmdParser.cpp
   stubs/FileHandle_stub.cpp
-  stubs/mbed_assert_stub.c
+  stubs/mbed_assert_stub.cpp
   stubs/mbed_poll_stub.cpp
 )
diff --git a/UNITTESTS/stubs/mbed_assert_stub.c b/UNITTESTS/stubs/mbed_assert_stub.cpp
similarity index 79%
rename from UNITTESTS/stubs/mbed_assert_stub.c
rename to UNITTESTS/stubs/mbed_assert_stub.cpp
index 426413a95b..875ef8792d 100644
--- a/UNITTESTS/stubs/mbed_assert_stub.c
+++ b/UNITTESTS/stubs/mbed_assert_stub.cpp
@@ -17,9 +17,14 @@
 
 #include "platform/mbed_assert.h"
 #include <stdio.h>
+#include <stdbool.h>
 
-void mbed_assert_internal(const char *expr, const char *file, int line)
+bool mbed_assert_throw_errors = false;
+
+extern "C" void mbed_assert_internal(const char *expr, const char *file, int line)
 {
     fprintf(stderr, "mbed assertation failed: %s, file: %s, line %d \n", expr, file, line);
+    if (mbed_assert_throw_errors) {
+        throw 1;
+    }
 }
-
diff --git a/UNITTESTS/target_h/platform/mbed_assert.h b/UNITTESTS/target_h/platform/mbed_assert.h
index 3d7a8a24d8..a8ff37564b 100644
--- a/UNITTESTS/target_h/platform/mbed_assert.h
+++ b/UNITTESTS/target_h/platform/mbed_assert.h
@@ -50,6 +50,12 @@ void mbed_assert_internal(const char *expr, const char *file, int line);
 }
 #endif
 
+/**
+ * For unittests: Global flag to select whether MBED_ASSERT
+ * throws error. Default false.
+ */
+extern bool mbed_assert_throw_errors;
+
 /** MBED_ASSERT
  *  Declare runtime assertions: results in runtime error if condition is false
  *
@@ -63,18 +69,12 @@ void mbed_assert_internal(const char *expr, const char *file, int line);
  *  }
  *  @endcode
  */
-#if defined( NDEBUG ) && !defined (MBED_WDOG_ASSERT)
-#define MBED_ASSERT(expr) ((void)0)
-#else
 #define MBED_ASSERT(expr)                                \
 do {                                                     \
     if (!(expr)) {                                       \
         mbed_assert_internal(#expr, __FILE__, __LINE__); \
     }                                                    \
 } while (0)
-#endif
-
-
 
 /** MBED_STATIC_ASSERT
  *  Declare compile-time assertions, results in compile-time error if condition is false