diff --git a/tests/plat/dup_e.e b/tests/plat/dup_e.e
index c0e0001b3..649589d84 100644
--- a/tests/plat/dup_e.e
+++ b/tests/plat/dup_e.e
@@ -2,8 +2,10 @@
     mes 2, EM_WSIZE, EM_PSIZE
 
 /*
- * Test _dup_ and _dus_ by loading 20 bytes from _src_, then making
- * and checking some duplicates.
+ * Tests _dup_ and _dus_ by loading 20 bytes from _src_, then making
+ * and checking some duplicates.  The compilers might never _dup_ or
+ * _dus_ with large sizes, so the compilers might work even if this
+ * test fails.  You can cheat this test if _cms_ always pushes zero.
  */
 
     exa src
diff --git a/tests/plat/exg_e.e b/tests/plat/exg_e.e
index 617f07104..455256483 100644
--- a/tests/plat/exg_e.e
+++ b/tests/plat/exg_e.e
@@ -2,8 +2,10 @@
     mes 2, EM_WSIZE, EM_PSIZE
 
 /*
- * Test _exg_ by loading 40 bytes from _src_, then exchanging 20 and
- * 20 bytes, and checking the result.
+ * Tests _exg_ by loading 40 bytes from _src_, then exchanging 20 and
+ * 20 bytes, and checking the result.  The compilers might never _exg_
+ * large sizes, so the compilers might work even if this test fails.
+ * You can cheat this test if _cms_ always pushes zero.
  */
 
     exa src
diff --git a/tests/plat/rotate_e.e b/tests/plat/rotate_e.e
index a6f8f28dd..0698c58a0 100644
--- a/tests/plat/rotate_e.e
+++ b/tests/plat/rotate_e.e
@@ -2,12 +2,16 @@
     mes 2, EM_WSIZE, EM_PSIZE
 
 /*
- * Test _rol_ (rotate left) and _ror_ (rotate right).
+ * Tests _rol_ (rotate left) and _ror_ (rotate right).  Several back
+ * ends provide _rol_ and _ror_, but as of year 2017, the compilers
+ * and optimizers had never emit _rol_ nor _ror_.
  *
  * By tradition, _rol_ and _ror_ can't rotate values shorter than the
  * word size, or longer than 4 bytes.
  *  - If word size is 2, then try rotating 2-byte and 4-byte values.
  *  - If word size is 4, then try rotating 4-byte values.
+ *
+ * You can cheat this test if _cmu_ always pushes zero.
  */
 
 #if EM_WSIZE == 2