-SBCL_HOME="$SBCL_PWD/../contrib"
-SBCL_CORE="$SBCL_PWD/../output/sbcl.core"
-SBCL_RUNTIME="$SBCL_PWD/../src/runtime/sbcl"
-SBCL_ARGS="--noinform --no-sysinit --no-userinit --noprint --disable-debugger"
+SBCL_HOME="${TEST_SBCL_HOME:-$SBCL_PWD/../contrib}"
+SBCL_CORE="${TEST_SBCL_CORE:-$SBCL_PWD/../output/sbcl.core}"
+SBCL_RUNTIME="${TEST_SBCL_RUNTIME:-$SBCL_PWD/../src/runtime/sbcl}"
+SBCL_ARGS="${TEST_SBCL_ARGS:---noinform --no-sysinit --no-userinit --noprint --disable-debugger}"