Greeting

Hey guys, how've you been? It's AC, Alexandre Calaça here. Hope you enjoy this new article.

Introduction

This article Don't Let Slow Specs Slow You Down: How to Identify them [Part II] is the second part of a series dedicated to talk about rspec tests. Just in case you didn't not check part I, just click here.

The next article is going to be Don't Let Slow Specs Slow You Down: How to Identify and Optimize Your RSpec Tests.

How to Identify

Slow specs in RSpec are specs that take longer than the average time to run. They can slow down your test suite and make it harder to get quick feedback on your code changes.

Basically, it's possible to use the --profile option and the gemrspec-benchmark gem.

In case you want to go deeper into this topic, please check the first part of the series: Don't Let Slow Specs Slow You Down: How to Identify them [Part I].

The --profile approach

Basic Usage

The rspec --profile command is used to run an RSpec test suite with profiling enabled, which provides a report of the slowest examples (tests) and groups (test suites) in the test suite. The profiling information is sorted by the execution time, with the slowest examples and groups listed at the top.

By default, it will automatically record the execution time of each example and group in your test suite, and then output a report of the 10 slowest examples and groups, along with their execution times.

Syntax

The basic usage is by running the following command in the terminal:

rspec --profile

In case you want to go deeper into this topic, please check the first part of the series: Don't Let Slow Specs Slow You Down: How to Identify them [Part I].

Customize sorting

By default, RSpec sorts the profiling results by execution time, with the slowest examples and groups listed at the top. However, you can use the --sort option to change the sorting method

By impact

Impact is a combination of the number of times an example is run and the average execution time.

It would be like this:

rspec --profile --sort impact

The previous command is going to sort the examples and groups with the highest impact (i.e., the ones that are run the most frequently and/or take the longest to execute) will be listed at the top.

By alphabetical order

rspec --profile --sort name

The previous command will sort the profiling results alphabetically by example or group name.

By the fastest

It sorts the profiling results by execution time in ascending order. So, it starts with the fastest examples and groups. This is the contrary of the Rspec's default sorting method, which is the slowest examples and groups listed at the top.

Take a look at a complete output example for the fastest sorting method:

Top 10 (fastest) examples:

  User
    creates a new user in the database (0.003 seconds)
    updates an existing user in the database (0.004 seconds)
    deletes a user from the database (0.005 seconds)

  Post
    creates a new article in the database (0.006 seconds)
    updates an existing article in the database (0.007 seconds)
    deletes an article from the database (0.008 seconds)

  Comment
    creates a new comment on an article (0.010 seconds)
    updates an existing comment on an article (0.011 seconds)
    deletes a comment from an article (0.012 seconds)

The previous output examples shows us the top 10 fastest examples, along with their execution times, grouped by the corresponding spec file and example description.

The --sort fastest option allows us to identify areas of our code that are performing well and may not require further optimization.

In case you want to be even more specific, you can customize the number of examples:

rspec --profile --sort fastest -n 30

By following the codebase's order

The --sort defined argument sorts the results by the order in which the examples are defined in the codebase, not by the Rspec's default, which is the execution time.

It's definitely an interesting way of visualizing your tests, since it follows the same order of the codebase.

This is an example of sorting the first 20 examples implemented in the codebase.

rspec --profile --sort defined -n 20

By ramdonly

This can help you identify potential issues that may not have been apparent when using other sorting methods.

In order to used, the --sort random argument must be used with the --profile option.

Take a look at an example:

rspec --profile --sort random

Complete list

It's possible to see a list of all the available sorting options for RSpec using the --help option. In this case, grep needs to be used.

Check it out:

rspec --help | grep sort

Calculate average time

To calculate the average time to run a spec in RSpec, you can use the --profile option with a specified number of examples. By default, RSpec will output the top 10 slowest examples. However, you can specify a different number of examples to output by using the -p or --profile option followed by the number of examples you want to see. The following command is configured to be 20 examples:

COPY

rspec --profile 20

Using this approach, you can sum the execution time of the first and the last example and get an average.

It's possible to sum the execution time of all elements and divide by the number of items.

It's also possible to get the element in the middle and consider it as the average.

There are many ideas and you need to choose the best for you.

In this article, we're not using the gemrspec-benchmark to accomplish this.

Celebrate

If you read the article, kudos! you did a great job. You can definitely celebrate!

Summary

The first article of the series focused on introducing the topic, the authors of rspec, and rspec itself. Besides, it showed several ways to identify slow rspec tests.

This article, which is the second part of the series, focused on how to customize sorting.

Conclusion

That's all for today. Thanks for reading the article Don't Let Slow Specs Slow You Down: How to Identify them [Part II].

This article is the second part of a series dedicated to talk about rspec tests. Just in case you didn't not check part I, just click here. The next article is going to be Don't Let Slow Specs Slow You Down: How to Identify and Optimize Your RSpec Tests.

I hope this article helped you. Let me know if you have any questions.

Your thoughts, suggestions and corrections are more than welcome.

By the way, feel free to drop your suggestions on new blog articles.

Hope to see you next time.