Add test for duplicates

run_tests

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+#
+
+errors=0
+
+for file in ./tests/* ; do
+    if [[ -e "$file" ]] ; then
+        echo "$file"
+        echo "--"
+        bash "$file" ; ((errors += $?))
+        echo ""
+    fi
+done
+
+if [[ "$errors" -ne 0 ]] ; then
+    echo "Test failures: $errors"
+    exit "$errors"
+fi

tests/no_dupes

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+#
+
+exts="$(dircolors LS_COLORS | head -n1 | sed 's/=[^:]*//g ; s/:/\n/g')"
+exts_sorted="$(sort <<< "$exts")"
+exts_uniq="$(sort -u <<< "$exts")"
+
+diff --color=auto --text --report-identical-files <(echo "$exts_uniq") <(echo "$exts_sorted")