Add changelog entry

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/ChangeLog.d/tests-common-code.txt b/ChangeLog.d/tests-common-code.txt
new file mode 100644
index 0000000..0af2da5
--- /dev/null
+++ b/ChangeLog.d/tests-common-code.txt
@@ -0,0 +1,5 @@
+Changes
+   * The unit tests now rely on header files in tests/include/test and source
+     files in tests/src. When building with make or cmake, the files in
+     tests/src are compiled and the resulting object linked into each test
+     executable.