Even trivial things like a typo in the method name in a method call are not detected at compile time by languages like JavaScript or Ruby (since their "method c

Even trivial things like a typo in the method name in a method call are not detected at compile time by languages like JavaScript or Ruby (since their "method calls" are in fact just lookups in a runtime hash table...). If you have not seen them, the reason is probably that the code was tested well enough before you looked for the bugs.