diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index 7642670fb..9d428a87c 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -354,6 +354,29 @@ jobs:
           make install -j Q=
       - name: Run tests
         shell: C:\cygwin\bin\env.exe CYGWIN_NOWINPATH=1 CHERE_INVOKING=1 C:\cygwin\bin\bash.exe -o igncr '{0}'
-        run: | # Allow asm/test.sh to run `git describe` for the version test
-          git config --global --add safe.directory '*'
+        run: |
           test/run-tests.sh --only-internal
+
+  freebsd:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+      - name: Build & test using CMake on FreeBSD
+        uses: vmactions/freebsd-vm@v1
+        with:
+          release: "15.0"
+          usesh: true
+          prepare: |
+            pkg install -y \
+              bash \
+              bison \
+              cmake \
+              git \
+              png
+          run: | # FreeBSD `c++` compiler does not support `make develop` sanitizers ASan or UBSan
+            cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER=c++ -DUSE_EXTERNAL_TESTS=OFF
+            cmake --build build -j4 --verbose
+            cmake --install build --verbose
+            cmake --build build --target test
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index b75d8a362..d49b6deba 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,10 +1,14 @@
 # SPDX-License-Identifier: MIT
 
-OPTION(USE_NONFREE_TESTS "run tests that build nonfree codebases" ON)
+option(USE_NONFREE_TESTS "run tests that build nonfree codebases" ON)
+option(USE_EXTERNAL_TESTS "run tests that build external codebases" ON)
 
 if(NOT USE_NONFREE_TESTS)
   set(ONLY_FREE "--only-free")
 endif()
+if(NOT USE_EXTERNAL_TESTS)
+  set(ONLY_INTERNAL "--only-internal")
+endif()
 
 add_executable(randtilegen gfx/randtilegen.cpp)
 add_executable(rgbgfx_test gfx/rgbgfx_test.cpp)
@@ -27,6 +31,6 @@ foreach(TARGET randtilegen rgbgfx_test)
 endforeach()
 
 add_test(NAME all
-         COMMAND ./run-tests.sh ${ONLY_FREE}
+         COMMAND ./run-tests.sh ${ONLY_FREE} ${ONLY_INTERNAL}
          WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
 )
diff --git a/test/CTestCustom.cmake.in b/test/CTestCustom.cmake.in
index cf70cb23d..95465b99f 100644
--- a/test/CTestCustom.cmake.in
+++ b/test/CTestCustom.cmake.in
@@ -1 +1 @@
-set(CTEST_CUSTOM_PRE_TEST "bash -c 'cd @CMAKE_CURRENT_SOURCE_DIR@\; ./fetch-test-deps.sh @ONLY_FREE@'")
+set(CTEST_CUSTOM_PRE_TEST "bash -c 'cd @CMAKE_CURRENT_SOURCE_DIR@\; ./fetch-test-deps.sh @ONLY_FREE@ @ONLY_INTERNAL@'")
diff --git a/test/fetch-test-deps.sh b/test/fetch-test-deps.sh
index a49e13c07..a3b8d14b0 100755
--- a/test/fetch-test-deps.sh
+++ b/test/fetch-test-deps.sh
@@ -6,16 +6,18 @@ cd "$(dirname "$0")"
 usage() {
 	echo "Downloads source code of Game Boy programs used as RGBDS test cases."
 	echo "Options:"
-	echo "    -h, --help      show this help message"
-	echo "    --only-free     download only freely licensed codebases"
-	echo "    --get-deps      install programs' own dependencies instead of themselves"
-	echo "    --get-hash      print programs' commit hashes instead of downloading them"
-	echo "    --get-paths     print programs' GitHub paths instead of downloading them"
+	echo "    -h, --help          show this help message"
+	echo "    --only-free         download only freely licensed codebases"
+	echo "    --only-internal     do not download any codebases"
+	echo "    --get-deps          install programs' own dependencies instead of themselves"
+	echo "    --get-hash          print programs' commit hashes instead of downloading them"
+	echo "    --get-paths         print programs' GitHub paths instead of downloading them"
 }
 
 # Parse options in pure Bash because macOS `getopt` is stuck
 # in what util-linux `getopt` calls `GETOPT_COMPATIBLE` mode
 nonfree=true
+external=true
 actionname=
 osname=
 while [[ $# -gt 0 ]]; do
@@ -27,6 +29,9 @@ while [[ $# -gt 0 ]]; do
 		--only-free)
 			nonfree=false
 			;;
+		--only-internal)
+			external=false
+			;;
 		--get-deps)
 			actionname="$1"
 			shift
@@ -97,6 +102,10 @@ case "$actionname" in
 		}
 esac
 
+if ! "$external"; then
+	exit
+fi
+
 if "$nonfree"; then
 	action pret  pokecrystal      2024-12-28 86a87a355e6805663cfecf150a3af71c66441a3e
 	action pret  pokered          2024-12-26 f023c68417ff0b14db1ab28ecff67f8d123ede44
diff --git a/test/run-tests.sh b/test/run-tests.sh
index e29d3a601..163ae3d5b 100755
--- a/test/run-tests.sh
+++ b/test/run-tests.sh
@@ -24,10 +24,11 @@ while [[ $# -gt 0 ]]; do
 			;;
 		--only-free)
 			nonfree=false
-			FETCH_TEST_DEPS="fetch-test-deps.sh --only-free"
+			FETCH_TEST_DEPS="$FETCH_TEST_DEPS --only-free"
 			;;
 		--only-internal)
 			external=false
+			FETCH_TEST_DEPS="$FETCH_TEST_DEPS --only-internal"
 			;;
 		--)
 			break