tests: add -help for command-line options

Add a help message for the test suite, documenting available options,
defaults, and backward-compatible positional arguments.

Author: furszy

src/unit_test.c

@@ -73,6 +73,22 @@ static int parse_arg(const char* key, const char* value, struct Args* out) {
     return 0;
 }
 
+static void help(void) {
+    printf("Usage: ./tests [options]\n\n");
+    printf("Run the test suite for the project with optional configuration.\n\n");
+    printf("Options:\n");
+    printf("    -help                           Show this help message and exit\n");
+    printf("    -j=<num>, -jobs=<num>           Number of parallel worker processes (default: 0 = sequential)\n");
+    printf("    -iter=<num>, -iterations=<num>  Number of iterations for each test (default: 64)\n");
+    printf("    -seed=<hex>                     Set a specific RNG seed (default: random)\n");
+    printf("\n");
+    printf("Notes:\n");
+    printf("    - All arguments must be provided in the form '-key=value'.\n");
+    printf("    - Unknown arguments are reported but ignored.\n");
+    printf("    - Sequential execution occurs if -jobs=0 or unspecified.\n");
+    printf("    - The first two positional arguments (iterations and seed) are also supported for backward compatibility.\n");
+}
+
 static int parse_jobs_count(const char* key, const char* value, struct Args* out) {
     char* ptr_val;
     long val = strtol(value, &ptr_val, 10); /* base 10 */
@@ -259,6 +275,12 @@ int main(int argc, char** argv) {
             _exit(EXIT_FAILURE);
         }
 
+        /* Check if we need to print help */
+        if (argv[1] && strcmp(argv[1], "-help") == 0) {
+            help();
+            _exit(EXIT_SUCCESS);
+        }
+
         /* Compatibility Note: The first two args were the number of iterations and the seed. */
         /* If provided, parse them and adjust the starting index for named arguments accordingly. */
         if (argv[1] && argv[1][0] != '-') {