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Providing Reproduction Steps
Phabricator Contributor Documentation (Contributing in Detail)

Describes how to provide reproduction steps.

Overview

When you submit a bug report about Phabricator, you MUST include reproduction steps. We can not help you with bugs we can not reproduce, and will not accept reports which omit reproduction steps or have incomplete or insufficient instructions.

This document explains what we're looking for in good reproduction steps. Briefly:

  • Reproduction steps must allow us to reproduce the problem locally on a clean, up-to-date install of Phabricator.
  • Reproduction should be as simple as possible.

Good reproduction steps can take time to write out clearly, simplify, and verify. As a reporter, we expect you to shoulder as much of this burden as you can, to make make it easy for us to reproduce and resolve bugs.

We do not have the resources to pursue reports with limited, inaccurate, or incomplete reproduction steps, and will not accept them. These reports require large amounts of our time and are often fruitless.

Example Reproduction Steps

Here's an example of what good reproduction steps might look like:


Reproduction steps:

  • Click "Create Event" in Calendar.
  • Fill in the required fields with any text (name, description, etc).
  • Set an invalid time for one of the dates, like the meaningless string "Tea Time". This is not valid, so we're expecting an error when we submit the form.
  • Click "Create" to save the event.

Expected result:

  • Form reloads with an error message about the specific mistake.
  • All field values are retained.

Actual result:

  • Form reloads with an error message about the specific mistake.
  • Most values are discarded, so I have to re-type the name, description, etc.

These steps are complete and self-contained: anyone can reproduce the issue by following these steps. These steps are clear and easy to follow. These steps are also simple and minimal: they don't include any extra unnecessary steps.

Finally, these steps explain what the reporter expected to happen, what they observed, and how those behaviors differ. This isn't as important when the observation is an obvious error like an exception, but can be important if a behavior is merely odd or ambiguous.

Reliable Reproduction

When you file a bug report, the first thing we do to fix it is to try to reproduce the problem locally on an up-to-date install of Phabricator. We will do this by following the steps you provide. If we can recreate the issue locally, we can almost always resolve the problem (often very promptly).

However, many reports do not have enough information, are missing important steps, or rely on data (like commits, users, other projects, permission settings, feed stories, etc) that we don't have access to. We either can't follow these steps, or can't reproduce issues by following them.

Reproduction steps must be complete and self-contained, and must allow anyone to reproduce the issue on a new, empty install of Phabricator. If the bug you're seeing depends on data or configuration which would not be present on a new install, you need to include that information in your steps.

For example, if you're seeing an issue which depends on a particular policy setting or configuration setting, you need to include instructions for creating the policy or adjusting the setting in your steps.

Getting Started

To generate reproduction steps, first find a sequence of actions which reproduce the issue you're seeing reliably.

Next, write down everything you did as clearly as possible. Make sure each step is self-contained: anyone should be able to follow your steps, without access to private or proprietary data.

Now, to verify that your steps provide a complete, self-contained way to reproduce the issue, follow them yourself on a new, empty, up-to-date instance of Phabricator.

If you can't easily start an empty instance locally, you can launch an empty instance on Phacility in about 60 seconds (see the "Resources" section for details).

If you can follow your steps and reproduce the issue on a clean instance, we'll probably be able to follow them and reproduce the issue ourselves.

If you can't follow your steps because they depend on information which is not available on a clean instance (for example, a certain config setting), rewrite them to include instructions to create that information (for example, adjusting the config to the problematic value).

If you follow your instructions but the issue does not reproduce, the issue might already be fixed. Make sure your install is up to date.

If your install is up to date and the issue still doesn't reproduce on a clean install, your reproduction steps are missing important information. You need to figure out what key element differs between your install and the clean install.

Once you have working reproduction steps, your steps may have details which aren't actually necessary to reproduce the issue. You may be able to simplify them by removing some steps or describing steps more narrowly. For help, see "Simplifying Steps" below.

Resources

We provide some resources which can make it easier to start building steps, or to simplify steps.

Phacility Test Instances: You can launch a new, up-to-date instance of Phabricator on Phacility in about a minute at https://admin.phacility.com. These instances run stable.

You can use these instances to make sure that issues haven't already been fixed, that they reproduce on a clean install, or that your steps are really complete, and that the root cause isn't custom code or local extensions. Using a test instance will avoid disrupting other users on your install.

Test Repositories: There are several test repositories on secure.phabricator.com which you can push commits to if you need to build an example to demonstrate a problem.

For example, if you're seeing an issue with a certain filename but the commit where the problem occurs is in a proprietary internal repository, push a commit that affects a file with a similar name to a test repository, then reproduce against the test data. This will allow you to generate steps which anyone can follow.

Simplifying Steps

If you aren't sure how to simplify reproduction steps, this section has some advice.

In general, you'll simplify reproduction steps by first finding a scenario where the issue reproduces reliably (a "bad" case) and a second, similar situation where it does not reproduce (a "good" case). Once you have a "bad" case and a "good" case, you'll change the scenarios step-by-step to be more similar to each other, until you have two scenarios which differ only a very small amount. This remaining difference usually points clearly at the root cause of the issue.

For example, suppose you notice that you get an error if you commit a file named A Banana.doc, but not if you commit a file named readme.md. In this case, A Banana.doc is your "bad" case and readme.md is your "good" case.

There are several differences between these file names, and any of them might be causing the problem. To narrow this down, you can try making the scenarios more similar. For example, do these files work?

  • A_Banana.doc - Problem with spaces?
  • A Banana.md - File extension issue?
  • A Ban.doc - Path length issue?
  • a banana.doc - Issue with letter case?

Some of these probably work, while others might not. These could lead you to a smaller case which reproduces the problem, which might be something like this:

  • Files like a b, which contain spaces, do not work.
  • Files like a.doc, which have the .doc extension, do not work.
  • Files like AAAAAAAAAA, which have more than 9 letters, do not work.
  • Files like A, which have uppercase letters, do not work.

With a simpler reproduction scenario, you can simplify your steps to be more tailored and minimal. This will help us pinpoint the issue more quickly and be more certain that we've understood and resolved it.

It is more important that steps be complete than that they be simple, and it's acceptable to submit complex instructions if you have difficulty simplifying them, so long as they are complete, self-contained, and accurately reproduce the issue.

Things to Avoid

These are common mistakes when providing reproduction instructions:

Insufficient Information: The most common issue we see is instructions which do not have enough information: they are missing critical details which are necessary in order to follow them on a clean install.

Inaccurate Steps: The second most common issue we see is instructions which do not actually reproduce a problem when followed on a clean, up-to-date install. Verify your steps by testing them.

Private Information: Some users provide reports which hinge on the particulars of private commits in proprietary repositories we can not access. This is not useful, because we can not examine the underlying commit to figure out why it is causing an issue.

Instead, reproduce the issue in a public repository. There are several test repositories available which you can push commits to in order to construct a reproduction case.

Screenshots: Screenshots can be helpful to explain a set of steps or show what you're seeing, but they usually aren't sufficient on their own because they don't contain all the information we need to reproduce them.

For example, a screenshot may show a particular policy or object, but not have enough information for us rebuild a similar object locally.

Alternatives

If you have an issue which you can't build reproduction steps for, or which only reproduces in your environment, or which you don't want to narrow down to a minimal reproduction case, we can't accept it as a bug report. These issues are tremendously time consuming for us to pursue and rarely benefit more than one install.

If the issue is important but falls outside the scope of permissible bug reports, we're happy to provide more tailored support at consulting rates. See Consulting for details.

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