R devel - Mar 2013 - techniques for mocking

I've been trying to set up a mocking framework to use in testing, in
conjunction with testthat.  I come from a java background.

What I've settled on is calling methods(class=klass), adding a
"mock" to
the name and assigning a function that returns null to the new name in the
base environment.  I've needed to assign it to the base environment because
the package environments are locked, and when code is executed in the
package environment, it doesn't have access to any new environment I give
it.  Unfortunately, this litters the base environment with meaningless
names that I can't then delete.

Is this the best approach?  Does anybody else use mocking code in their
testing?

Thank you,

Dan

PS Some basic code:

#' @export
mock <- function(klass, ...) {
new_methods <- list(...);
lapply(methods(class=klass), function(method_name) {
if (method_name %in% names(new_methods)) {
new_method <- new_methods[[method_name]];
} else {
new_method <- function() NULL;
}
formals(new_method) <- formals(method_name);
assign(mocked_name(method_name), new_method, baseenv());
});
}

#' @export
mocked_object <- function(klass) {
x <- list();
class(x) <- mocked_name(klass);
return(x);
}

#' @export
clean_base <- function(klass) {
lapply(methods(class=mocked_name(klass)), function(name) {
assign(name, NULL, envir=baseenv())
});
}

mocked_name <- function(name) {paste0(name, "mock")};

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