1. A method of validating translated files for inclusion in an application being developed, the method comprising the steps of: a computer sending a translatable file having externalized content in a single base natural language to a plurality of other computers, wherein the externalized content is external to code of the application being developed; in response to a generation of a first translated file including a first translation of the externalized content into a natural language other than the base natural language by another computer included in the plurality of other computers, the computer receiving the first translated file from the other computer; in a simulation environment, a processor of the computer simulating a loading of the first translation of the externalized content into a user interface of the application at a runtime of the application and simulating a presentation of the first translation of the externalized content in the user interface at the runtime, by calling one or more functions included in the application, without an actual presentation of the first translation of the externalized content in the user interface, wherein an execution at the runtime of the one or more functions displays the externalized content in the user interface; the computer determining whether the simulating of the loading of the first translation of the externalized content into the user interface and the simulating of the presentation of the first translation of the externalized content in the user interface by the calling the one or more functions indicates an error condition that causes the application to stop running at the runtime; based in part on the error condition being indicated by the simulating of the loading of the first translation and the simulating of the presentation of the first translation, the computer: determining the first translation of the externalized content includes a syntax error that causes the error condition, and initiating a correction of the syntax error by sending the report to the other computer, wherein the syntax error includes at least one of: (1) a first key included in the first translated file is not matched with exactly one corresponding first value in the first translated file, the first translated file being a first property file including first key-value pairs including the first key and the first value as one of the pairs; (2) a second key in the translatable file is not in the first translated file, the translatable file being a second property file including second key-value pairs, one of the second key-value pairs including the second key; and (3) one or more placeholders in the first translated file are not matched to respective one or more placeholders in the translatable file, the one or more placeholders in the first translated file and the one or more placeholders in the translatable file providing variable substitution by being filled in with actual values by the code of the application at the runtime; and in response to a receipt by the computer of a second translation of the externalized content which includes the correction of the syntax error, the second translation included in a second translated file generated by the other computer: the computer simulating a loading of the second translation of the externalized content into the user interface of the application at the runtime and simulating a presentation of the second translation of the externalized content in the user interface at the runtime, by calling the one or more functions; the computer determining whether the simulating of the loading of the second translation and the simulating of the presentation of the second translation by the calling the one or more functions indicates the error condition that causes the application to stop running at the runtime; and based in part on the error condition not being indicated by the simulating of the loading of the second translation and the simulating of the presentation of the second translation, the computer at the runtime presenting the second translation of the externalized content in the user interface without causing the application to stop running at the runtime.