Change test_main to run a single test case out of the suite

By passing the name of the test function on the command line
we execute exactly that one test, and then exit successfully
if the test did not fail.  This permits multiple functions in
the same .c file, so they could be called from a shell script
or debugged independently externally.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

tests/test_main.c

@@ -29,11 +29,36 @@
 #define BEGIN_TEST(name) extern void testfunc__##name(void);
 #include TEST_TOC
 
+struct test_def {
+	const char *name;
+	void (*fun)(void);
+};
+struct test_def all_tests[] = {
+#   undef BEGIN_TEST
+#   define BEGIN_TEST(name) {#name, testfunc__##name},
+#   include TEST_TOC
+	{NULL, NULL}
+};
+
 int main(int argc, char **argv)
 {
-#undef BEGIN_TEST
-#define BEGIN_TEST(name) testfunc__##name();
-#include TEST_TOC
+	struct test_def *t;
 
-	return 0;
+	if (argc == 1) {
+		for (t = all_tests; t->name; t++)
+			t->fun();
+		return 0;
+	} else if (argc == 2) {
+		for (t = all_tests; t->name; t++) {
+			if (!strcmp(t->name, argv[1])) {
+				t->fun();
+				return 0;
+			}
+		}
+		fprintf(stderr, "error: No test '%s' in %s\n", argv[1], argv[0]);
+		return 1;
+	} else {
+		fprintf(stderr, "usage: %s [test_name]\n", argv[0]);
+		return 1;
+	}
 }