close some gaps in the type system

std/arraylist/arraylist.test.bro

@@ -7,6 +7,7 @@ handles_append test {
 
 	try append(&list, 42)
 
+	try testing.expect_type(usize, list.items.len)
 	try testing.expect_equal(1, list.items.len)
 	try testing.expect_equal(42, list.items[0])
 }

std/testing/testing.bro

@@ -24,6 +24,10 @@ expect_equal func($T type, expected, actual T, location SourceLocation) void ! E
 	}
 }
 
+expect_type func($Expected, $Actual type, _ Actual, location SourceLocation) void ! Error {
+	try expect($(Expected == Actual), location)
+}
+
 run func(name []u8, callback *func() void ! Error) bool {
 	callback() catch |_| {
 		debug.print("{s} [failed]\n", {name,})