Fix msg argument to assert_equal

I noticed this was taking an argument but not dealing with it.  In
general the functions were undocumented, so I added some terse usage.

Also, the intent of the test-case was to expand the values before
using them as the message; make sure this happens by using a temp
variable.

Change-Id: Ib317ad1e9dd2a5d2232b9c64541fe4a601a2b8da
diff --git a/tests/test_truefalse.sh b/tests/test_truefalse.sh
index ebd9650..2689589 100755
--- a/tests/test_truefalse.sh
+++ b/tests/test_truefalse.sh
@@ -19,7 +19,8 @@
 
     for default in True False; do
         for name in one captrue lowtrue uppertrue capyes lowyes upperyes; do
-                assert_equal "True" $(trueorfalse $default $name) "\$(trueorfalse $default $name)"
+            local msg="trueorfalse($default $name)"
+            assert_equal "True" $(trueorfalse $default $name) "$msg"
         done
     done
 
@@ -33,7 +34,8 @@
 
     for default in True False; do
         for name in zero capfalse lowfalse upperfalse capno lowno upperno; do
-            assert_equal "False" $(trueorfalse $default $name) "\$(trueorfalse $default $name)"
+            local msg="trueorfalse($default $name)"
+            assert_equal "False" $(trueorfalse $default $name) "$msg"
         done
     done
 }