Google Testing Blog

Code Health: Providing Context with Commit Messages and Bug Reports

Monday, September 11, 2017

This is another post in our Code Health series. A version of this post originally appeared in Google bathrooms worldwide as a Google Testing on the Toilet episode. You can download a printer-friendly version to display in your office.
By Chris Lewis
You are caught in a trap. Mechanisms whirl around you, but they make no sense. You desperately search the room and find the builder's original plans! The description of the work order that implemented the trap reads, "Miscellaneous fixes." Oh dear.
Reading other engineers' code can sometimes feel like an archaeology expedition, full of weird and wonderful statements that are hard to decipher. Code is always written with a purpose, but sometimes that purpose is not clear in the code itself. You can address this knowledge gap by documenting the context that explains why a change was needed. Code comments provide context, but comments alone sometimes can’t provide enough.
There are two key ways to indicate context:Commit Messages

A commit message is one of the easiest, most discoverable means of providing context. When you encounter lines of code that may be unclear, checking the commit message which introduced the code is a great way to gain more insight into what the code is meant to do.

Write the first line of the commit message so it stands alone, as tools like GitHub will display this line in commit listing pages. Stand-alone first lines allow you to skim through code history much faster, quickly building up your understanding of how a source file evolved over time. Example:

Add Frobber to the list of available widgets.

This allows consumers to easily discover the new Frobber widget and
add it to their application.

Bug Reports

You can use a bug report to track the entire story of a bug/feature/refactoring, adding context such as the original problem description, the design discussions between the team, and the commits that are used to solve the problem. This lets you easily see all related commits in one place, and allows others to easily keep track of the status of a particular problem.
Most commits should reference a bug report. Standalone commits (e.g. one-time cleanups or other small unplanned changes) don't need their own bug report, though, since they often contain all their context within the description and the source changes.

Informative commit messages and bug reports go hand-in-hand, providing context from different perspectives. Keep in mind that such context can be useful even to yourself, providing an easy reminder about the work you did last week, last quarter, or even last year. Future you will thank past you!

3 comments

Code Health: Eliminate YAGNI Smells

Monday, August 14, 2017

This is another post in our Code Health series. A version of this post originally appeared in Google bathrooms worldwide as a Google Testing on the Toilet episode. You can download a printer-friendly version to display in your office.
By Marc Eaddy
The majority of software development costs are due to maintenance. One way to reduce maintenance costs is to implement something only when you actually need it, a.k.a. the “You Aren't Gonna Need It” (YAGNI) design principle. How do you spot unnecessary code? Follow your nose!
A code smell is a code pattern that usually indicates a design flaw. For example, creating a base class or interface with only one subclass may indicate a speculation that more subclasses will be needed in the future. Instead, practice incremental development and design: don't add the second subclass until it is actually needed.
The following C++ code has many YAGNI smells:

class Mammal { ...
  virtual Status Sleep(bool hibernate) = 0;
};
class Human : public Mammal { ...
  virtual Status Sleep(bool hibernate) {
    age += hibernate ? kSevenMonths : kSevenHours;
    return OK;
  }
};

Maintainers are burdened with understanding, documenting, and testing both classes when only one is really needed. Code must handle the case when hibernate is true, even though all callers pass false, as well as the case when Sleep returns an error, even though that never happens. This results in unnecessary code that never executes. Eliminating those smells simplifies the code:

class Human { ...
  void Sleep() { age += kSevenHours; }
};

Here are some other YAGNI smells:

Code that has never been executed other than by tests (a.k.a. code that is dead on arrival)
Classes designed to be subclassed (have virtual methods and/or protected members) that are not actually subclassed
Public or protected methods or fields that could be private
Parameters, variables, or flags that always have the same value

Thankfully, YAGNI smells, and code smells in general, are often easy to spot by looking for simple patterns and are easy to eliminate using simple refactorings.

Are you thinking of adding code that won't be used today? Trust me, you aren't gonna need it!

1 comment

Code Health: To Comment or Not to Comment?

Monday, July 17, 2017

This is another post in our Code Health series. A version of this post originally appeared in Google bathrooms worldwide as a Google Testing on the Toilet episode. You can download a printer-friendly version to display in your office.
By Dori Reuveni and Kevin Bourrillion
While reading code, often there is nothing more helpful than a well-placed comment. However, comments are not always good. Sometimes the need for a comment can be a sign that the code should be refactored.
Use a comment when it is infeasible to make your code self-explanatory. If you think you need a comment to explain what a piece of code does, first try one of the following:

Introduce an explaining variable.

// Subtract discount from price.
finalPrice = (numItems * itemPrice)
    - min(5, numItems) * itemPrice * 0.1;

price = numItems * itemPrice;
discount =
    min(5, numItems) * itemPrice * 0.1;
finalPrice = price - discount;

Extract a method.

// Filter offensive words.
for (String word : words) { ... }

filterOffensiveWords(words);

Use a more descriptive identifier name.

int width = ...; // Width in pixels.

int widthInPixels = ...;

Add a check in case your code has assumptions.

// Safe since height is always > 0.
return width / height;

checkArgument(height > 0);
return width / height;

There are cases where a comment can be helpful:

Reveal your intent: explain why the code does something (as opposed to what it does).

// Compute once because it’s expensive.
Protect a well-meaning future editor from mistakenly “fixing” your code.

// Create a new Foo instance because Foo is not thread-safe.
Clarification: a question that came up during code review or that readers of the code might have.

// Note that order matters because...
Explain your rationale for what looks like a bad software engineering practice.

@SuppressWarnings("unchecked") // The cast is safe because...

On the other hand, avoid comments that just repeat what the code does. These are just noise:

// Get all users.
userService.getAllUsers();

// Check if the name is empty.
if (name.isEmpty()) { ... }

10 comments

Evolution of GTAC and Engineering Productivity

Wednesday, July 12, 2017

When Google first hosted GTAC in 2006, we didn’t know what to expect. We kicked off this conference with the intention to share our innovation in test automation, learn from others in the industry and connect with academia. Over the last decade we’ve had great participation and had the privilege to host GTAC in North America, Europe and Asia -- largely thanks to the many of you who spoke, participated and connected!
In the recent months, we’ve been taking a hard look at the discipline of Engineering Productivity as a logical next step in the evolution of test automation. In that same vein, we’re going to rethink what an Engineering Productivity focused conference should look like today. As we pivot, we will be extending these changes to GTAC and because we expect changes in theme, content and format, we are canceling the upcoming event scheduled in London this November. We’ll be bringing the event back in 2018 with a fresh outlook and strategy.
While we know this may be disappointing for many of the folks who were looking forward to GTAC, we’re excited to come back with a new format which will serve this conference well in today’s environment.

34 comments

Code Health: Too Many Comments on Your Code Reviews?

Monday, June 19, 2017

This is another post in our Code Health series. A version of this post originally appeared in Google bathrooms worldwide as a Google Testing on the Toilet episode. You can download a printer-friendly version to display in your office.
By Tom O'Neill
Code reviews can slow down an individual code change, but they’re also an opportunity to improve your code and learn from another intelligent, experienced engineer. How can you get the most out of them? Aim to get most of your changes approved in the first round of review, with only minor comments. If your code reviews frequently require multiple rounds of comments, these tips can save you time.
Spend your reviewers’ time wisely—it’s a limited resource. If they’re catching issues that you could easily have caught yourself, you’re lowering the overall productivity of your team. Before you send out the code review:

Re-evaluate your code: Don’t just send the review out as soon as the tests pass. Step back and try to rethink the whole thing—can the design be cleaned up? Especially if it’s late in the day, see if a better approach occurs to you the next morning. Although this step might slow down an individual code change, it will result long-term in greater average throughput.

Consider an informal design discussion: If there’s something you’re not sure about, pair program, talk face-to-face, or send an early diff and ask for a “pre-review” of the overall design.

Self-review the change: Try to look at the code as critically as possible from the standpoint of someone who doesn’t know anything about it. Your code review tool can give you a radically different view of your code than the IDE. This can easily save you a round trip.

Make the diff easy to understand: Multiple changes at once make the code harder to review. When you self-review, look for simple changes that reduce the size of the diff. For example, save significant refactoring or formatting changes for another code review.

Don’t hide important info in the submit message: Put it in the code as well. Someone reading the code later is unlikely to look at the submit message.

When you’re addressing code review comments:

Re-evaluate your code after addressing non-trivial comments: Take a step back and really look at the code with fresh eyes. Once you’ve made one set of changes, you can often find additional improvements that are enabled or suggested by those changes. Just as with any refactoring, it may take several steps to reach the best design.

Understand why the reviewer made each comment: If you don’t understand the reasoning behind a comment, don’t just make the change—seek out the reviewer and learn something new.

Answer the reviewer’s questions in the code: Don’t just reply—make the code easier to understand (e.g., improve a variable name, change a boolean to an enum) or add a comment. Someone else is going to have the same question later on.

15 comments

Testing Blog

Code Health: Providing Context with Commit Messages and Bug Reports

Code Health: Eliminate YAGNI Smells

Code Health: To Comment or Not to Comment?

Evolution of GTAC and Engineering Productivity

Code Health: Too Many Comments on Your Code Reviews?

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