How To Have Different Return Values For Multiple Calls On A Jasmine Spy

When working with Jasmine spies in your testing environment, you might encounter scenarios where you need to set up different return values for multiple calls to the same spy. This can be a handy feature when you want your spy to simulate different behaviors based on each call.

Thankfully, Jasmine provides a simple way to achieve this using the `and.returnValues()` function. This function allows you to specify an array of return values that the spy will cycle through in the order they are provided. Let's walk through how you can implement this in your test cases.

First, create a spy using Jasmine's `jasmine.createSpy()` function. This sets up a new spy object that we can then configure with specific return values for multiple calls. For example, let's say we have a spy called `mySpy`:

const mySpy = jasmine.createSpy('mySpy');

Next, we can use the `and.returnValues()` function to define different return values for `mySpy` for each call. Here's an example:

mySpy.and.returnValues('First call', 'Second call', 'Third call');

In this example, when `mySpy` is called for the first time, it will return `'First call'`. For the second call, it will return `'Second call'`, and for the third call, it will return `'Third call'`. After the third call, the spy will loop back to the first value.

You can provide any number of return values in the array passed to `and.returnValues()`. Jasmine will cycle through these values accordingly. This feature is especially useful when you are testing functions or methods that are expected to behave differently with each subsequent call.

Here's an example test case demonstrating the usage of multiple return values with a Jasmine spy:

it('should return different values for multiple calls', () => {
  mySpy.and.returnValues(1, 2, 3);

  expect(mySpy()).toBe(1); // First call
  expect(mySpy()).toBe(2); // Second call
  expect(mySpy()).toBe(3); // Third call
  expect(mySpy()).toBe(1); // After the third call, it cycles back to the first value
});

By setting up different return values for multiple calls on a Jasmine spy, you can enhance the flexibility and precision of your test cases. This feature allows you to simulate diverse scenarios in your testing environment, ensuring that your code behaves as expected under various conditions.

In conclusion, leveraging the `and.returnValues()` function in Jasmine provides a convenient way to customize the return values of your spies for each call. Experiment with this feature in your test suite to create more comprehensive and robust test cases for your software projects.