Clean up and improve gzip unit tests

* Switch some test_eq parameters so the expected is always the first parameter
* Drop some manual checks of compressed format magic numbers (they're pointless
  and they make the unit tests less readable and more fragile, considering
  we're already indirectly checking those magic numbers via the
  detect_compression_method function)
* Add a couple of extra assertions

src/test/test_util.c

@@ -954,13 +954,14 @@ test_util_gzip(void)
     test_assert(!tor_gzip_compress(&buf2, &len1, buf1, strlen(buf1)+1,
                                    GZIP_METHOD));
     test_assert(buf2);
-    test_assert(!memcmp(buf2, "\037\213", 2)); /* Gzip magic. */
+    test_assert(len1 < strlen(buf1));
     test_assert(detect_compression_method(buf2, len1) == GZIP_METHOD);
 
     test_assert(!tor_gzip_uncompress(&buf3, &len2, buf2, len1,
                                      GZIP_METHOD, 1, LOG_INFO));
     test_assert(buf3);
-    test_streq(buf1,buf3);
+    test_eq(strlen(buf1) + 1, len2);
+    test_streq(buf1, buf3);
 
     tor_free(buf2);
     tor_free(buf3);
@@ -969,13 +970,13 @@ test_util_gzip(void)
   test_assert(!tor_gzip_compress(&buf2, &len1, buf1, strlen(buf1)+1,
                                  ZLIB_METHOD));
   test_assert(buf2);
-  test_assert(!memcmp(buf2, "\x78\xDA", 2)); /* deflate magic. */
   test_assert(detect_compression_method(buf2, len1) == ZLIB_METHOD);
 
   test_assert(!tor_gzip_uncompress(&buf3, &len2, buf2, len1,
                                    ZLIB_METHOD, 1, LOG_INFO));
   test_assert(buf3);
-  test_streq(buf1,buf3);
+  test_eq(strlen(buf1) + 1, len2);
+  test_streq(buf1, buf3);
 
   /* Check whether we can uncompress concatenated, compressed strings. */
   tor_free(buf3);
@@ -983,7 +984,7 @@ test_util_gzip(void)
   memcpy(buf2+len1, buf2, len1);
   test_assert(!tor_gzip_uncompress(&buf3, &len2, buf2, len1*2,
                                    ZLIB_METHOD, 1, LOG_INFO));
-  test_eq(len2, (strlen(buf1)+1)*2);
+  test_eq((strlen(buf1)+1)*2, len2);
   test_memeq(buf3,
              "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAZAAAAAAAAAAAAAAAAAAAZ\0"
              "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAZAAAAAAAAAAAAAAAAAAAZ\0",
@@ -1002,8 +1003,8 @@ test_util_gzip(void)
   /* when we allow an incomplete string, we should succeed.*/
   tt_assert(!tor_gzip_uncompress(&buf3, &len2, buf2, len1-16,
                                   ZLIB_METHOD, 0, LOG_INFO));
-  buf3[len2]='\0';
   tt_assert(len2 > 5);
+  buf3[len2]='\0';
   tt_assert(!strcmpstart(buf1, buf3));
 
   /* when we demand a complete string, this must fail. */
@@ -1024,19 +1025,20 @@ test_util_gzip(void)
   len2 = 21;
   test_assert(tor_zlib_process(state, &cp1, &len1, &ccp2, &len2, 0)
               == TOR_ZLIB_OK);
-  test_eq(len2, 0); /* Make sure we compressed it all. */
+  test_eq(0, len2); /* Make sure we compressed it all. */
   test_assert(cp1 > buf1);
 
   len2 = 0;
   cp2 = cp1;
   test_assert(tor_zlib_process(state, &cp1, &len1, &ccp2, &len2, 1)
               == TOR_ZLIB_DONE);
-  test_eq(len2, 0);
+  test_eq(0, len2);
   test_assert(cp1 > cp2); /* Make sure we really added something. */
 
   tt_assert(!tor_gzip_uncompress(&buf3, &len2, buf1, 1024-len1,
                                   ZLIB_METHOD, 1, LOG_WARN));
   test_streq(buf3, "ABCDEFGHIJABCDEFGHIJ"); /*Make sure it compressed right.*/
+  test_eq(21, len2);
 
  done:
   if (state)