Writing unit tests for I/O functions in Rust [duplicate]

This question already has an answer here:

• How to create an in-memory object that can be used as a Reader, Writer, or Seek in Rust? 3 answers
• How can I locate resources for testing with Cargo? 1 answer

In C++, I have often used the following pattern to create testable functions:

MyType readfile(std::ostream& file) {
    // Read file and do stuff
    return MyType;
}

MyType readfile(const std::string& filename) {
     std::ofstream file(filename);
     return readfile(file);
}

This allows me to test the reading of the file by constructing a file in memory by using a std::stringstream and sending it to the first overload of the function. I could read a secondary test file, but I have found this pattern to be convenient.

Is there any idiomatic way to accomplish the same thing in Rust?

If I have to create some test data, then where is the standard location to keep this data in a Rust project?