How to start Terminator with split screens and custom commands running
Starting Terminator with split screens is quite simple: Just store a layout and start Terminator with the --layout <your layout> option.
However, if you want to run custom commands in your terminals, you need to do some work to keep these terminals from closing after a command exits. You accomplish this by tweaking bash to run a command before actually starting.
Pimp your .bashrc
Add this to the end of .bashrc:
# hack to keep a bash open when starting it with a command
[[ $startup_cmd ]] && { declare +x $startup_cmd; eval...
RSpec 3 allows chaining multiple expectations
When you are using lambdas in RSpec to assert certain changes of a call, you know this syntax:
expect { playlist.destroy }.to change { Playlist.count }.by(-1)
While you can define multiple assertions through multiple specs, you may not want to do so, e.g. for performance or for the sake of mental overhead.
RSpec allows chaining expectations simply by using and.
expect { playlist.destroy }
.to change { Playlist.count }.by(-1)
.and change { Video.count }.by(0)
The above example will call playlist.destroy only...
Cheat Sheet for the modern DOM API
See the attached link for a useful overview of modern (and classic) DOM API methods, like matches, contains, append, cssText, etc.
You will still need to look up some documentation, e.g. on how to modify a ClassList, but it's still better than browsing interfaces and superclasses of Element on MDN without knowing what to look for.
When coming from jQuery, also see the card on JavaScript without jQuery. This card includes a link to [You Don't Need jQuery](https://github.com/nefe/You-Dont-Need-jQuery/blob/maste...
Spreewald development steps
Our gem spreewald Archive supports a few helpers for development. In case you notice errors in your Cucumber tests, you might want to use one of them to better understand the underlying background of the failure. The following content is also part of the spreewald's README Archive , but is duplicated to this card to allow repeating.
Then console
Pauses test execution and opens an IRB shell with current cont...
Simple database lock for MySQL
Note: For PostgreSQL you should use advisory locks. For MySQL we still recommend the solution in this card.
If you need to synchronize multiple rails processes, you need some shared resource that can be used as a mutex. One option is to simply use your existing (MySQL) database.
The attached code provides a database-based model level mutex for MySQL. You use it by simply calling
Lock.acquire('string to synchronize on') do
# non-t...
Debugging AJAX requests with better_errors
better_errors
Archive
is an awesome gem for enhanced error pages in development, featuring a live-REPL for some light debugging.
To debug the exception you got on an AJAX-Request, visit /__better_errors on your app's root path (e.g. http://localhost:3000/__better_errors). It shows the error page for the last exception that occurred, even when it has been triggered by an AJAX request.
How Rails chooses error pages (404, 500, ...) for exceptions
When your controller action raises an unhandled exception, Rails will look at the exception's class and choose an appropriate HTTP status code and error page for the response.
For instance, an ActiveRecord::RecordNotFound will cause Rails to render a red "The page you were looking for doesn't exist" with a status code of "404" (not found).
The mapping from exception classes to error types is a hash in Rails.configuration.action_dispatch.rescue_responses. The...
Heads up: RSpec's diffs may not tell the truth
RSpec provides a nice diff when certain matchers fail.
Here is an example where this diff is helpful while comparing two hashes:
{a:1}.should match(a:1, b:2)
Failure/Error: {a:1}.should match(a:1, b:2)
expected {:a=>1} to match {:a=>1, :b=>2}
Diff:
@@ -1,3 +1,2 @@
:a => 1,
-:b => 2,
Unfortunately, this diff is not as clever as it would need to. RSpec's instance_of matchers will look like errors in the diff (even if they are not), and time objects that differ only in milliseconds won't appear in the ...
Ruby: What extend and include do
All Rubyists should be familiar with the common definitions for include and extend. You include a module to add instance methods to a class and extend to add class methods. Unfortunately, this common definition isn’t entirely accurate. It fails to explain why we use instance.extend(Module) to add methods to an instance. Shouldn’t it be instance.include(Module)? To figure this out we’re going to start by discussing where methods are stored.
- include: Adds methods from the provided Module to the object
- extend: Calls include on the single...
Selenium: Network throttling via Chromedriver
You can throttle the network in your headless chrome via Selenium. This might be useful for debugging issues with flaky integration tests or slow page simulations.
page.driver.browser.network_conditions = {offline: false, latency: 5, download_throughput: 2 * 1024, upload_throughput: 2 * 1024}
The settings will match to the following UI component in Chrome:
Were the values for the default profiles might match the values from this post Archive :
**S...
List of Chromium Command Line Switches « Peter Beverloo
An extensive list of command line options when booting Chrome.
This is useful for building a Capybara driver with custom Chrome options.
Use the Git stash without shooting yourself in the foot
The Git stash does not work like a one-slot clipboard and you might shoot yourself in the foot if you pretend otherwise.
In particular git stash apply does not remove the stashed changes from the stash. That means you will probably apply the wrong stash when you do git stash apply after a future stashing.
To keep your stash clean, you can use
git stash pop
instead.
Another way to look at it:
git stash pop
is the same as
git stash apply && git stash drop
Notice: In case of a conflict git will not pop th...