diff --git a/src/globals/ext-tests/brotli.php b/src/globals/ext-tests/brotli.php
index 2b24941d..bfe9f259 100644
--- a/src/globals/ext-tests/brotli.php
+++ b/src/globals/ext-tests/brotli.php
@@ -2,7 +2,14 @@
 
 declare(strict_types=1);
 
-$str = 'brotli_compress ( string $data, int $level = BROTLI_COMPRESS_LEVEL_DEFAULT, int $mode = BROTLI_GENERIC, string|null $dict = null ): string|false';
 assert(function_exists('brotli_compress'));
 assert(function_exists('brotli_uncompress'));
-assert(brotli_uncompress(brotli_compress($str)) === $str);
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = brotli_compress($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = brotli_uncompress($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);
diff --git a/src/globals/ext-tests/bz2.php b/src/globals/ext-tests/bz2.php
index 7550bee1..f5402dcf 100644
--- a/src/globals/ext-tests/bz2.php
+++ b/src/globals/ext-tests/bz2.php
@@ -2,7 +2,14 @@
 
 declare(strict_types=1);
 
-$str = 'This is bz2 extension test';
-assert(function_exists('bzdecompress'));
 assert(function_exists('bzcompress'));
-assert(bzdecompress(bzcompress($str, 9)) === $str);
+assert(function_exists('bzdecompress'));
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = bzcompress($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = bzdecompress($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);
diff --git a/src/globals/ext-tests/xz.php b/src/globals/ext-tests/xz.php
index bae345fa..5f7503d7 100644
--- a/src/globals/ext-tests/xz.php
+++ b/src/globals/ext-tests/xz.php
@@ -2,7 +2,14 @@
 
 declare(strict_types=1);
 
-$str = 'Data you would like compressed.';
 assert(function_exists('xzencode'));
 assert(function_exists('xzdecode'));
-assert(xzdecode(xzencode($str)) === $str);
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = xzencode($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = xzdecode($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);
diff --git a/src/globals/ext-tests/zlib.php b/src/globals/ext-tests/zlib.php
index 1fae531f..699fc759 100644
--- a/src/globals/ext-tests/zlib.php
+++ b/src/globals/ext-tests/zlib.php
@@ -3,4 +3,13 @@
 declare(strict_types=1);
 
 assert(function_exists('gzcompress'));
-assert(gzdecode(gzencode('aaa')) === 'aaa');
+assert(function_exists('gzdecode'));
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = gzcompress($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = gzdecode($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);
diff --git a/src/globals/ext-tests/zstd.php b/src/globals/ext-tests/zstd.php
new file mode 100644
index 00000000..3ebaf2a2
--- /dev/null
+++ b/src/globals/ext-tests/zstd.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+assert(function_exists('zstd_compress'));
+assert(function_exists('zstd_uncompress'));
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = zstd_compress($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = zstd_uncompress($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);