why different variables within RSpec?

Question

What is the difference between using a local variable, an instance variable, and one created with the 'let' method inside RSpec tests?

Answer 1

Using a let is the best choice if you need to reuse the variable, otherwise a local variable may make more sense. But you can decide for yourself given the differences:

Local variable

Only accessible from within one test, i.e. it cannot be reused.

Instance variable

Accessible from all tests within the example group. Assigned and evaluated on every test run in example group.

Let

Accessible from all tests within the example group. Lazily evaluated so it is only created (and the code to create it) when it is actually used in a test.

A let may still make sense instead of a local variable if the variable logically belongs to a context or describe block rather than an individual test—but that's preference based on test structure.