add memory usage tests

tests/python/tests/memory_usage/php/data/component-config.yaml

@@ -0,0 +1,7 @@
+entry: script
+components:
+  script:
+    image: KPHP
+    scope: Request
+    args: {}
+    links: {}

tests/python/tests/memory_usage/php/index.php

@@ -0,0 +1,49 @@
+<?php
+
+function memory_work() {
+  $a = "a";
+
+  $n = 1e6;
+  for ($i = 1; $i < $n; ++$i) {
+    $a .= "a";
+  }
+
+  return $a;
+}
+
+function test_memory_usage() {
+  $base_usage = memory_get_usage(false);
+
+  $a = memory_work();
+
+  var_dump(memory_get_usage(false) - $base_usage);
+
+  unset($a);
+
+  var_dump(memory_get_usage(false) - $base_usage);
+  var_dump(memory_get_peak_usage(false) - $base_usage);
+}
+
+function test_total_memory_usage() {
+  $base_usage = memory_get_total_usage();
+
+  $a = memory_work();
+
+  var_dump(memory_get_total_usage() - $base_usage);
+
+  unset($a);
+
+  var_dump(memory_get_total_usage() - $base_usage);
+  var_dump(memory_get_peak_usage(true) - $base_usage);
+}
+
+switch($_SERVER["PHP_SELF"]) {
+  case "/test_memory_usage":
+    test_memory_usage();
+    break;
+  case "/test_total_memory_usage":
+    test_total_memory_usage();
+    break;
+  default:
+    critical_error('unexpected "' . $_SERVER["PHP_SELF"] . '"');
+}

tests/python/tests/memory_usage/test_memory_usage.py

@@ -0,0 +1,37 @@
+import pytest
+
+from python.lib.testcase import WebServerAutoTestCase
+
+
+class TestMemoryUsage(WebServerAutoTestCase):
+    def _template(self, test_case: str, expected_usage: int, expected_usage_after_unset: int, expected_peak_usage: int):
+        response = self.web_server.http_post(f"/{test_case}")
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            response.text,
+            "".join(
+                f"int({memory_usage})\n"
+                for memory_usage in [expected_usage, expected_usage_after_unset, expected_peak_usage]
+            ),
+        )
+
+    def test_memory_usage(self):
+        self._template("test_memory_usage", 2**20, 0, 2**19 + 2**20)
+
+    @pytest.mark.k2_skip
+    def test_total_memory_usage_kphp(self):
+        self._template(
+            "test_total_memory_usage",
+            48 + sum(2**n for n in range(12, 21)),
+            48 + sum(2**n for n in range(12, 20)),
+            48 + sum(2**n for n in range(12, 21)),
+        )
+
+    @pytest.mark.kphp_skip
+    def test_total_memory_usage_k2(self):
+        self._template(
+            "test_total_memory_usage",
+            96 + sum(2**n for n in range(12, 21)),
+            96 + sum(2**n for n in range(12, 20)),
+            96 + sum(2**n for n in range(12, 21)),
+        )