RustG version + log format unit tests

code/modules/unit_tests/log_format.dm

@@ -0,0 +1,26 @@
+// This exists so that logs are the designated format. If they arent, it breaks logging tooling. Also 8601 is king.
+#define TEST_MESSAGE "Log time format test"
+#define TEST_LOG_FILE "data/ci_testing.log"
+
+/proc/generate_test_log_message(time)
+	var/date_portion = time2text(time, "YYYY-MM-DD")
+	var/time_portion = time2text(time, "hh:mm:ss")
+	return "\[[date_portion]T[time_portion]] [TEST_MESSAGE]"
+
+
+/datum/unit_test/rustg_version/Run()
+	// Generate a list of valid log timestamps. It can be the current time, or up to 2 seconds later to account for spurious CI lag
+	var/valid_lines = list(
+		"[generate_test_log_message(world.timeofday)]",
+		"[generate_test_log_message(world.timeofday + 10)]",
+		"[generate_test_log_message(world.timeofday + 20)]",
+	)
+
+	rustg_log_write(TEST_LOG_FILE, TEST_MESSAGE)
+
+	var/list/lines = file2list(TEST_LOG_FILE)
+	if(!(lines[1] in valid_lines))
+		Fail("RUSTG log format is not valid 8601 format. Expected '[generate_test_log_message(world.timeofday)]', got '[lines[1]]'")
+
+#undef TEST_MESSAGE
+#undef TEST_LOG_FILE