diff --git a/.travis.yml b/.travis.yml
index 884b3ab..5b32599 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -35,7 +35,11 @@
 
 addons:
   apt:
+    sources:
+      - sourceline: 'deb https://apt.kitware.com/ubuntu/ focal main'
+        key_url: 'https://apt.kitware.com/keys/kitware-archive-latest.asc'
     packages:
+    - cmake
     - ninja-build
     - libncursesw5
 
@@ -279,3 +283,41 @@
             | while read file; do python ./hal/tests/pinvalidate/pinvalidate.py -vfp "${file}"; done
         - git diff --exit-code --diff-filter=d --color
 
+    ### CMake Check ###
+    - &cmake-vm
+      stage: "CMake Check"
+      name: "Backward compatiblity check - MBED_TEST_MODE"
+      env: NAME=mbed-test-mode-check ROOT=tools/cmake/tests/mbed_test_mode/ TOOLCHAIN=GCC_ARM TARGET_NAME=K64F PROFILE=develop
+      language: python
+      python: 3.8
+      install:
+        # Hide Travis-preinstalled CMake
+        # The Travis-preinstalled CMake is unfortunately not installed via apt, so we
+        # can't replace it with an apt-supplied version very easily. Additionally, we
+        # can't permit the Travis-preinstalled copy to survive, as the Travis default
+        # path lists the Travis CMake install location ahead of any place where apt
+        # would install CMake to. Instead of apt removing or upgrading to a new CMake
+        # version, we must instead delete the Travis copy of CMake.
+        - sudo rm -rf /usr/local/cmake*
+        # Setup ccache
+        - ccache -o compiler_check=content
+        - ccache -M 1G
+        - pushd /usr/lib/ccache
+        - sudo ln -s ../../bin/ccache arm-none-eabi-gcc
+        - sudo ln -s ../../bin/ccache arm-none-eabi-g++
+        - export PATH="/usr/lib/ccache:$PATH"
+        - popd
+        # Install arm-none-eabi-gcc
+        - pushd /home/travis/build && mkdir arm-gcc && cd arm-gcc
+        - curl -L0 "https://developer.arm.com/-/media/Files/downloads/gnu-rm/9-2020q2/gcc-arm-none-eabi-9-2020-q2-update-x86_64-linux.tar.bz2?revision=05382cca-1721-44e1-ae19-1e7c3dc96118&la=en&hash=D7C9D18FCA2DD9F894FD9F3C3DC9228498FA281A" --output gcc-arm-none-eabi-9-2020-q2-update.tar.bz2
+        - tar xf gcc-arm-none-eabi-9-2020-q2-update.tar.bz2
+        - export PATH="$PATH:${PWD}/gcc-arm-none-eabi-9-2020-q2-update/bin"
+        - popd
+        - arm-none-eabi-gcc --version
+        # Install python modules
+        - pip install --upgrade mbed-tools
+        - pip install -r tools/cmake/requirements.txt
+      script:
+        - mbedtools configure -p ${ROOT} -t ${TOOLCHAIN} -m ${TARGET_NAME} --mbed-os-path .
+        - cmake -S ${ROOT} -B ${ROOT}/cmake_build/${TARGET_NAME}/${PROFILE}/${TOOLCHAIN}/ -GNinja -DCMAKE_BUILD_TYPE=${PROFILE}
+        - cmake --build ${ROOT}/cmake_build/${TARGET_NAME}/${PROFILE}/${TOOLCHAIN}/
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a06c29..63c80e8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,6 +79,14 @@
         ${MBED_CONFIG_DEFINITIONS}
 )
 
+# Add MBED_TEST_MODE for backward compatibility with Greentea tests written for use with Mbed CLI 1
+if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME AND BUILD_TESTING)
+    target_compile_definitions(${PROJECT_NAME}
+        PUBLIC
+            MBED_TEST_MODE
+    )
+endif()
+
 # We need to generate a "response file" to pass to the C preprocessor when we preprocess the linker
 # script, because of path length limitations on Windows. We set the response file and bind the path
 # to a global property here. The MBED_TARGET being built queries this global property when it sets
diff --git a/tools/cmake/mbed_greentea.cmake b/tools/cmake/mbed_greentea.cmake
index baa182d..23fddc6 100644
--- a/tools/cmake/mbed_greentea.cmake
+++ b/tools/cmake/mbed_greentea.cmake
@@ -41,6 +41,9 @@
 
     add_executable(${TEST_NAME})
 
+    # Explicitly enable BUILD_TESTING until CTest is added to the Greentea client
+    set(BUILD_TESTING ON)
+
     mbed_configure_app_target(${TEST_NAME})
 
     target_include_directories(${TEST_NAME}
diff --git a/tools/cmake/tests/mbed_test_mode/CMakeLists.txt b/tools/cmake/tests/mbed_test_mode/CMakeLists.txt
new file mode 100644
index 0000000..d40c513
--- /dev/null
+++ b/tools/cmake/tests/mbed_test_mode/CMakeLists.txt
@@ -0,0 +1,21 @@
+# Copyright (c) 2020 ARM Limited. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.19.0 FATAL_ERROR)
+
+set(MBED_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../../../.. CACHE INTERNAL "")
+set(MBED_CONFIG_PATH ${CMAKE_CURRENT_BINARY_DIR} CACHE STATIC "")
+
+include(${MBED_PATH}/tools/cmake/app.cmake)
+
+add_test(NAME mbed-test-mode-check COMMAND mbed-test-mode-check)
+add_executable(mbed-test-mode-check)
+project(mbed-test-mode-check)
+
+set(PROJECT_NAME ${CMAKE_PROJECT_NAME} CACHE INTERNAL "")
+include(CTest)
+
+target_sources(mbed-test-mode-check
+    PRIVATE
+        main.cpp
+)
diff --git a/tools/cmake/tests/mbed_test_mode/main.cpp b/tools/cmake/tests/mbed_test_mode/main.cpp
new file mode 100644
index 0000000..8669da7
--- /dev/null
+++ b/tools/cmake/tests/mbed_test_mode/main.cpp
@@ -0,0 +1,13 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2021 Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#if BUILD_TESTING && !defined(MBED_TEST_MODE)
+#error "MBED_TEST_MODE not defined with BUILD_TESTING on"
+#else
+int main(){
+    return 0;
+}
+#endif