test/zlibutil: update to match changes in zlibutil, increase reliability

The following changes have been made:
- The test has been adjusted to zlibutil's changed behavior.
- The output of zlibutil isn’t checked against static data, instead it hands
  the compressed file to another decompressor. This was done because the exact
  output can change with updates to zlib itself (this appears to have happened
  in my case).
- The new test works with random data, reducing the likelihood of false passes.
- The new decompression test works with its own file for the same reason.

scripts/test/zlibutil.sh

@@ -1,26 +1,46 @@
 #!/usr/bin/env bash
 echo "================================================================================"
-echo -n "Testing \`zlibutil\`... "
+echo "Testing \`zlibutil\`:"
+echo "--------------------------------------------------------------------------------"
 
+TMPDIR="$(mktemp -d -t fossvg-zlibutil-XXXXX)"
+TMPDATA="$(dd if=/dev/urandom bs=33 count=1 2>/dev/null | base64)"
 
-echo "abc" >> testfile
+echo -n "Compression test... "
 
-bin/tools/zlibutil -c testfile
+echo -n "$TMPDATA" >> "$TMPDIR/compress"
+zlibutil "$TMPDIR/compress"
 
-if [ "$(bin/tools/arraydump --binary testfile.compressed)" = "{0b01111000, 0b10011100, 0b01001011, 0b01001100, 0b01001010, 0b11100110, 0b00000010, 0b00000000, 0b00000011, 0b01111110, 0b00000001, 0b00110001}" ]; then
-    echo -n "Compression Test: PASS... "
+python3 <<< "
+import zlib, sys
+tmpfile = open('$TMPDIR/compress.zz', 'rb')
+data = tmpfile.read()
+tmpfile.close()
+try:
+    if zlib.decompress(data)==b'$TMPDATA':
+        print('PASS')
+    else:
+        print('FAIL: Wrong data.')
+except:
+    print('FAIL: Exception.')
+"
+
+echo -n "Decompression test... "
+#TODO: create a compressed file using another implementation (Python)
+python3 <<< "
+import zlib
+tmpfile = open('$TMPDIR/decompress.zz', 'wb')
+tmpfile.write(zlib.compress(b'$TMPDATA'))
+tmpfile.close()
+"
+
+zlibutil -d "$TMPDIR/decompress.zz"
+if [ "$(cat "$TMPDIR/decompress")" = "$TMPDATA" ]; then
+    echo "PASS"
 else
-    echo -n "Compression Test: FAILED... "
+    echo "FAIL"
 fi
 
-bin/tools/zlibutil -d testfile.compressed
-
-if [ "$(bin/tools/arraydump --binary testfile.compressed.uncompressed)" = "{0b01100001, 0b01100010, 0b01100011, 0b00001010}" ]; then
-    echo "Decompression Test: PASS"
-else
-    echo "Decompression Test: FAILED"
-fi
-
-rm testfile testfile.compressed testfile.compressed.uncompressed
+rm -r "$TMPDIR"
 
 echo "================================================================================"