diff --git a/tests/common.shi b/tests/common.shi
new file mode 100644
index 0000000..0619341
--- /dev/null
+++ b/tests/common.shi
@@ -0,0 +1,10 @@
+# Test environment
+SRCDIR=`dirname $0`
+SRCDIR=`cd $SRCDIR && pwd`
+TOPSRCDIR=`cd $srcdir && pwd`
+REFERENCE_IMAGE="${TOPSRCDIR}/images/rose.pnm"
+. ./common.shi
+[ "X$CONVERT" = "X" ] && CONVERT=convert
+[ "X$IDENTIFY" = "X" ] && IDENTIFY=identify
+export SRCDIR TOPSRCDIR
+cd tests || exit 1