unit test: Always print the free memory delta after the test

Prevents situations where the leak threshold is low and the
value slowly creeps up to be close to it, without developer
noticing.

tools/unit-test-app/components/test_utils/test_runner.c

@@ -87,14 +87,17 @@ void setUp(void)
 
 static void check_leak(size_t before_free, size_t after_free, const char *type)
 {
-    printf("MALLOC_CAP_%s leak: Leak threshold is: %u \n",
-            type, 
-            critical_leak_threshold);
+    int free_delta = (int)after_free - (int)before_free;
+    printf("MALLOC_CAP_%s usage: Free memory delta: %d Leak threshold: -%u \n",
+           type,
+           free_delta,
+           critical_leak_threshold);
 
-    if (before_free <= after_free) {
-        return;
+    if (free_delta > 0) {
+        return; // free memory went up somehow
     }
-    size_t leaked = before_free - after_free;
+
+    size_t leaked = (size_t)(free_delta * -1);
     if (leaked <= warn_leak_threshold) {
         return;
     }
@@ -117,15 +120,15 @@ static bool leak_check_required(void)
         const char *sub_leaks = strstr(Unity.CurrentDetail1, leaks);
         if (sub_leaks != NULL) {
             if (sub_leaks[len_leaks] == ']') {
-                return true;
+                return false;
             } else if (sub_leaks[len_leaks] == '=') {
                 critical_leak_threshold = strtol(&sub_leaks[len_leaks + 1], NULL, 10);
                 warn_leak_threshold = critical_leak_threshold;
-                return false;
+                return true;
             }
         }
     }
-    return false;
+    return true;
 }
 
 /* tearDown runs after every test */
@@ -137,8 +140,6 @@ void tearDown(void)
     /* clean up some of the newlib's lazy allocations */
     esp_reent_cleanup();
 
-    size_t after_free_8bit = heap_caps_get_free_size(MALLOC_CAP_8BIT);
-    size_t after_free_32bit = heap_caps_get_free_size(MALLOC_CAP_32BIT);
     /* We want the teardown to have this file in the printout if TEST_ASSERT fails */
     const char *real_testfile = Unity.TestFile;
     Unity.TestFile = __FILE__;
@@ -152,9 +153,11 @@ void tearDown(void)
     heap_trace_dump();
 #endif
 
-    if (leak_check_required() == false) {
-        check_leak(before_free_8bit, after_free_8bit, "8BIT");
-        check_leak(before_free_32bit, after_free_32bit, "32BIT");
+    if (leak_check_required()) {
+          size_t after_free_8bit = heap_caps_get_free_size(MALLOC_CAP_8BIT);
+          size_t after_free_32bit = heap_caps_get_free_size(MALLOC_CAP_32BIT);
+          check_leak(before_free_8bit, after_free_8bit, "8BIT");
+          check_leak(before_free_32bit, after_free_32bit, "32BIT");
     }
 
     Unity.TestFile = real_testfile; // go back to the real filename