Using PowerShell to make BrowserStack local testing easier with Microsoft Edge

BrowserStack has been an incredibly useful resource for tracking down bugs and testing fixes when I am working on websites. This often requires accessing locally deployed sites or sites accessible over a VPN connection, and to do that, BrowserStack needs some local code running to be able to route the traffic accordingly.

BrowserStack logoUp until recently, my browser of choice has been Google Chrome, for which BrowserStack provides a handy extension to add support for local sites. However, since the Windows Creators Update, I have been giving Microsoft Edge a shot1 and no such extension exists. Instead, BrowserStack provides a download, BrowserStackLocal.exe , and a secret with which to run it. This works great, but there are a couple of annoyances.

  1. I have to remember to run it.
  2. It is a blocking process.

There are a variety of ways this problem can be solved. I decided to take the opportunity to expand my PowerShell fu and put together some cmdlets to run the BrowserStackLocal process in the background. Specifically, I wanted to compare PowerShell jobs with plain old processes for this specific purpose.

First: Jobs

Since the running the command is a blocking operation, I decided to try wrapping it in a PowerShell job so that it would sit in the background. This is useful since the job gets terminated when the PowerShell session ends, which makes it less likely for me to forget. The downside is that each PowerShell session could have its own job, but only the one that started BrowserStackLocal will actually end it, but I was certain I could work with that.

Getting started

The first cmdlet for starting BrowserStackLocal is cunningly named Start-BrowserStackLocal , shown here:

This has basic room for improvement, like having the secret and the path be parameters to the cmdlet, or environment variables; I happened to stop tinkering once it worked for me, so feel free to expand on it.

At the start, we check to see if we already have a job for BrowserStackLocal since we only need one. If we do not, then we get on with making sure BrowserStackLocal can be found where we expect it. If everything looks good, then the job gets started.

To tackle the chance that my script may fail due to the BrowserStackLocal command either getting an incorrect key or discovering it is already running, I added a Wait-Job call. The nice thing here is that since normally BrowserStackLocal blocks, we can assume that if the job did not reach a completion state, then the executable command is running. I take advantage of that fact, so if the Wait-Job returns, we can assume things went wrong and dump the details of the problem back to the console.

Stopping the job

Once the job is running, we need to be able to terminate it.

This is a much simpler cmdlet than the one to start the job. It has two main tasks:

  1. See if the job is actually running
  2. If it is, stop it

I added some helpful output so we could see it working and that was that.

Output from jobs-based cmdlets
Output from jobs-based cmdlets

Problems with jobs

This solution using jobs works great but it is not ideal. Each PowerShell session has its own jobs, so you have to know which session actually started BrowserStackLocal in order to stop it. Not only that, but if PowerShell did not start it at all, you cannot stop it from there with these commands at all. Jobs are great but they are not really the right tool for this…er…job.

Second: Processes

The wise man would have probably started here. I did not because I wanted to learn about jobs. Now that I have, I am wiser and so, I thought I would recreate my success but this time using the Xxx-Process  cmdlets of PowerShell.

Getting started again

Using processes, the start cmdlet looks like this:

Since the BrowserStackLocal executable starts more than one process, I added some loops to output information about those processes. Now if we try to start the command and it is already running, we will get the same feedback, regardless of where the command was started.

Stopping the process

Switching to processes makes the stop code a little more complicated, but only because I wanted to provide some additional detail (we could have just called Stop-Process BrowserStackLocal and it would stop all matching processes).

Output from process-based cmdlets
Output from process-based cmdlets

Helpful aliases

Finally, to make the task of starting and stopping a little less arduous, I added some aliases (inspired by the helpful sasv and spsv aliases of Start-Service and Stop-Service).

Conclusion

TL;DR: Use processes to start processes in the background2.

The rest

I am pretty pleased with how this little PowerShell project worked out. I get to keep using Microsoft Edge with minimal effort beyond what I had when using Google Chrome for my BrowserStack testing, enabling me to take advantage of the performance and battery-life improvements Edge has over Chrome. Not only that, but I got to learn some new things about PowerShell.

  1. You don't get closures entirely for free in PowerShell. I suspected this, but I learned the hard way. However…
  2. We can pass local variables into script blocks using the $using:<variable> syntax instead of passing an argument list and adding parameters to our script.
  3. Debugging jobs can be a pain until you learn the value of Receive-Job for getting error information.
  4. Use Wait-Job with a little time out to give your job chance to fail so that you can spit out some error information.
  5. You have to stop a job before you can remove it.
  6. Don't use jobs to control background processes; use processes instead

I have not gone so far yet as to start the BrowserStackLocal service automatically, but I can see value in doing so, especially if I did a lot of BrowserStack testing on local sites every day (of course, I'd probably want to redirect the output to $null in that scenario rather than see feedback on the running processes with every shell I opened).

What are your thoughts? Do you use PowerShell jobs? Do you use BrowserStack? Will you make use of these cmdlets? Fire off in the comments.


  1. Yes, the battery life is noticeably better than when using Chrome; yes, I am frustrated that I cannot clear cookies for a specific site 

  2. Well, duh. But if I had taken that attitude, I would not have learned about jobs. 

C#7: Tools

I have spent the first couple of months of 2017 learning about the new features in C#7. This would not have been possible without some tools to help me play around with the new language syntax and associated types. Since we have to wait a little longer until Visual Studio 2017 is released, I thought you might like to know what tools I have been using to tinker in all things C#7.

LINQPad Beta

Link: http://www.linqpad.net/Download.aspx#beta

While early releases of Visual Studio 2017 (scheduled for release on March 7th) support the language, I initially found the release candidate to be unstable and frustrating. Not only that, but it can be cumbersome to spin up a quick example using Visual Studio, so I turned to my trusty friend, LINQPad.

LINQPad Beta showing me my return is missing a ref
LINQPad Beta showing me my return is missing a ref

I cannot recommend LINQPad enough, it is a fantastic tool for prototyping, poking around data sources, and more besides, like tinkering with language features you don't yet understand. While LINQPad's current release only supports the C# language up to version 61, the beta release also supports C# version 7. Not only can you use the language, but with the fantastic analysis window, you can see how Roslyn breaks down each part of the code. If you want to get started quickly, easily play around with the cool new features, and have a powerful tool for digging deeper as the need arises, the LINQPad beta is the tool to get.

Visual Studio 2017 RC

Link: https://www.visualstudio.com/downloads/

Visual Studio 2017 RC splash
Visual Studio 2017 RC splash

Yes, I know I said it was unstable and frustrating, but that was before, way back in January. These days the RC is much, much better and with the release date set for March 7th, there was never a better time to install Visual Studio 2017 RC and get a head start on getting to know some of the new things it can do, including C# 7. Tuples are fun, but poking around with them in the debugger is funner.

OzCode

Link: https://oz-code.com/

Pattern matching in OzCode
Pattern matching in OzCode

It is no secret that I love OzCode, the magical debugging extension for Visual Studio. It is so well-known that they asked me to be part of their OzCode Magician community program. So, it should come as no surprise that I have been using OzCode in my exploration of C#7. As the Visual Studio 2017 RC has matured, the clever people over at CodeValue have been creating previews of OzCode version 3, including amazing LINQ debugging support. Recently, I got to try an internal build that included support for all the cool new things in C#7.

OzCode 3 will be released on March 7th, the same day as Visual Studio 2017.

Documentation

Link: https://docs.microsoft.com/dotnet/articles/csharp/csharp-7

Never underestimate the power of reading documentation, it is one of the best tools out there. For my C#7 posts, I relied heavily on the new docs.microsoft.com site, specifically the .NET articles on C#. Not only is this a fantastic resource, but it has built-in support for commenting on the documentation so that you can ask questions and contribute to their improvement.

In Conclusion

This is the entire list of tools I used for my C#7 investigations. Try them out and get an early start on C#7 fun before the March 7th release of all the C#7 goodness. Happy tinkering and if you stumble on any useful tools, please share in the comments!


  1. It also supports SQL, F#, and VB 

C#7: Tuples

Well, here we are; the final post in this series on the new C#7 features. Over the last six weeks we have covered all but one, including:

While pattern matching is exciting, local functions are useful, and some of the other enhancements are nice, I personally feel that I have saved the best for last, because this week it is time to look at tuples.

Tuples

Wait, don't we already have tuples in C#? I mean, we totally have a type called Tuple so it sure seems like it. In fact, we have at least one other tuple-type too, KeyValuePair<TKey,TValue>. However, these are not C# concepts, they are .NET types and they fall pretty short of being the kind of tuples we want. I did not know what was really wrong with them until I learned about the tuples we get with C#7.

It turns out, the old Tuple type is limited; the members have fixed names ( Item1, Item2, etc.) which do not communicate their purpose, it is a reference type and as such can have a measurable impact on performance due to object allocations, and it has no syntactical support within the language1. To support the new C#7 feature, there is a new tuple type that is more performant and better suited to the awesomeness that is C#7 tuples; it is a value-type called ValueTuple and it comes with some friends like TupleElementNamesAttribute to give us something wonderful.

If you want to play with C#7 tuples in Visual Studio 2017 RC, you'll need to grab the NuGet package so that the appropriate types to support tuples are available for the compiler. LINQPad Beta already includes everything you need.

Syntax

To define a new tuple in C#7, we use parentheses in an assignment like this:

This creates a new tuple that looks an awful lot like something we might have created using Tuple.Create("John", "Smith", 45, ConsoleColor.DarkRed), since the values of the tuple are referenced via Item1, Item2, Item3, and Item4. That does not seem like a particular useful addition. However, we can make this tuple so much better with some simple changes to our assignment, like this:

Now, instead of the ItemX members, we can access our values using FirstName, LastName, Age, and FavouriteConsoleColor, as if we had instead created an anonymous type. Of course, the great thing is that we did not introduce a new type to do this; the C# compiler pulled some magic along with the new ValueTuple type2 . Of course, it does not end there; we can take advantage of a new feature called deconstruction to name the fields on the left of the assignment instead:

In fact, we can provide names on both sides although the ones provided on the left take precedent and you will get a compiler warning. However, being able to provide names via the right-hand side of an assignment is useful when a method returns a tuple and you want to provide some meaningful names locally. This is even more useful when you find out that you can drop the tuple variable name:

We basically just assigned values to four local variables that we can then use in the rest of our code, but if we had a method like this:

We could do this on the right-hand side of that assignment:

What we did there was deconstruct the returned tuple into four separate fields. Our method declares its return type as ValueType<string, string, int, ConsoleColor>  and returns a tuple, then we assign that tuple to four variables by using the deconstruction syntax. In this example, I even switched to using var instead of explicitly typing the deconstruction. The var keyword can be used for all of the deconstructed fields, just a couple with the remainder strongly typed, or none; it's up to you and your code reviewers.

Deconstruction is going to change the way you write methods and some of your types, and will probably mean a lot less uses for out variables. That said, do not get carried away. Tuples are best for internal and private methods rather than public APIs where a static type is much more helpful to the consumer of your API.

The Deconstruct Method

If a method returns a tuple (e.g. return ("John", "Smith")), we can use deconstruction to assign its parts to different variables if we wish. However, deconstruction is not reserved for just tuples. We can also define how our own types can be deconstructed into separate variables. To do this, we define a Deconstruct method on our type that tells the compiler how to deconstruct it into separate values. For example:

With this type defined, we can use the deconstruction syntax with it just as we would with a ValueTuple:

I am not sure when I will use this ability to define deconstruction for my types, but I can imagine when the moment arises I will know. Also, you can see from its extensive use in the Deconstruct method, out is certainly not redundant.

Anonymous Types

Tuples in C#7 seem to out-do anonymous types in every way; tuples don't define a new type, they can be returned from methods without the overheads of object or dynamic, they support deconstruction, and they take up less typing; yet as far as I can tell they can be used everywhere that anonymous types can be used. It is likely that I am missing something important, but from my perspective thus far, I think tuples in C#7 not only kills off any new uses of the Tuple type, but also anonymous types.

In Conclusion

I really like this feature and the simplicity of its usage. It is light on extra syntax, adding the concept of a parenthetically-typed variable, but powerful in what it allows us to do with method returns and type deconstruction. I would like to give it some more thought and use it in more scenarios, but I also think tuples in C#7 will render anonymous types obsolete.

You can skim the overview of tuples in the What's new in C# 7 document, however, this is a simple feature with a complex background, so I highly recommend reading the more in-depth coverage on the Tuples official documentation, especially with regards to assignment of tuples with explicit member names3. It is a shame that it took two attempts to get tuples to be where they should be in C#, leaving yet another type4 by the wayside, but they are here at last and we will all be grateful.

What do you think? Are anonymous types relegated to legacy code only? Will Tuple.Create ever get used again? Is there something I should cover that is missing here or in the official documentation? Sound off in the comments and let me know.

 


  1. C# Concepts: Tuples 

  2. Actually, like dynamic, the field names use an attribute to communicate the names of each tuple field 

  3. Hint: member names are not attached to the value, but instead stay with the variable for which they were declared 

  4. Tuple.Create may never get used again 

C#7: Better Performance with Ref Locals, and Ref and Async Returns

Since the start of the year, we have been taking a look at the various new features coming to C# in C#7. This week, we will look at some of the changes to returning values from our functions that are there for those who need better performance. Before we begin, here is a summary of what we are covering in this series.

Generalized async return types

Up until now, an async method had to return Task, Task<T>, or void (though that last one is generally frowned upon1). However, returning Task or Task<T> can create performance bottlenecks as the reference type needs allocating. For C#7, we can now return other types from async methods, including the new ValueTask<T>, enabling us to have better control over these performance concerns. For more information, I recommend checking out the official documentation.

Ref Locals and Ref Returns

C#7 brings a variety of changes to how we get output from our methods; specifically, out variables, tuples, and ref locals and ref returns. I covered out variables in an earlier post and I will be covering tuples in the next one, so let's take a look at ref locals and ref returns. Like the changes to async return types, this feature is all about performance.

The addition of ref locals and ref returns enable algorithms that are more efficient by avoiding copying values, or performing dereferencing operations multiple times.2

Like many performance-related issues, it is difficult to come up with a simple real world example that is not entirely contrived. So, suspend your engineering minds for a moment and assume that this is a perfectly great solution for the problem at hand so that I can explain this feature to you. Imagine it is Halloween and we are counting how many pieces of candy we have collectively from all of our heaving bags of deliciousness3. We have several bags of candy with different candy types and we want to count them. So, for each bag, we group by candy type, then retrieve current count of each candy type, add the count of that type from the bag, and then store the new count.

This works, but it has overhead; we have to look up the candy count value in our dictionary multiple times when retrieving and setting the count. However, by using ref returns, we can create an alternative to our dictionary that minimises that overhead. In writing this example, I learned4 that since IDictionary does not do ref returns from its methods, we can't use it with ref locals directly. However, we also cannot use a local variable as we cannot return a reference to a value that does not live beyond the method call, so we must modify how we store our counts.

Now we are returning a reference to the actual stored value and changing it directly without repeated look-ups on our data type, making our algorithm perform better5. Be sure to check out the official documentation for alternative examples of usage.

Syntax Gotchas

Before we wrap this up, I want to take a moment to point out a few things about syntax. This feature uses the ref keyword a lot. You have to specify that the return type of a method is ref, that the return itself is a return ref, that the local variable storing the returned value is a ref, and that the method call is also ref. If you skip one of these uses of ref, the compiler will let you know, but as I discovered when writing the examples, the message is not particularly clear regarding how to fix it. Not only that, but you may get caught out when trying to consume by-reference returns as you can skip the two uses at the call-site (e.g. int count =_candyCounter.GetCount(candyName);); in such a case, the method call will be as if it were a regular, non-reference return; watch out.

In Conclusion

I doubt any of us will use these performance-related features much, if at all, and nor should we. In fact, I expect that their appearance will be a code smell in a majority of circumstances; a case of "ooo, shiny" usage6. I certainly think that the use of ref return with anything but value types will be highly unusual. That said, in those situations when every nanosecond of performance is required, these new C# additions will most definitely be invaluable.


  1. https://msdn.microsoft.com/en-us/magazine/jj991977.aspx 

  2. https://docs.microsoft.com/en-us/dotnet/articles/csharp/csharp-7#ref-locals-and-returns 

  3. Let's not focus on why we went trick or treating as adults and why anyone gave us candy in the first place 

  4. seems obvious now 

  5. In theory; after all, this is a convoluted example and I am sure there are better ways to improve performance than just using ref locals. Always measure your code to be sure you are making things better; don't guess 

  6. "Ooo, shiny" usage; when someone uses something just because it's new and they want to try it out 

C#7: Local Functions

We have been racing through the C#7 features in my latest series of posts; here is a list of what I have covered and what will be covered:

In today's post, we will look at local functions. Those who are familiar with JavaScript will be familiar with local functions; the ability to define a method inside of another method. We have had a similar ability in C# since anonymous methods were introduced albeit in a slightly less flexible form1. Up until C#7, methods defined within another method were assigned to variables and were limited in use and content. For example, one could not use yieldinside anonymous methods.

Local functions allow us to declare a method within the scope of another method; not as an assignment to a run-time variable as with anonymous methods and lambda expressions, but as a compile-time symbol to be referenced locally by its parent function. With lambda expressions, the compiler does some heavy lifting for us, creating an anonymous type to hold our method and its closures; also, to call them, a delegate must be instantiated and then invoked, which incurs additional memory overhead to standard method calls: none of this is necessary for local functions as they are regular methods. Not only that, but because these are regular methods, the full range of method syntax is available to us, including yield.

The official documentation provides a good overview of the differences between anonymous methods/lambda expressions and local functions, which ends with this paragraph:

While local functions may seem redundant to lambda expressions, they actually serve different purposes and have different uses. Local functions are more efficient for the case when you want to write a function that is called only from the context of another method.

The last sentence of that infers one of the most useful things about local methods; streaming enumerable sequences with fail early support. The yield syntax introduced in C#3 has been incredibly useful, simplifying the work necessary for defining an enumerator from writing an entire class to just writing a method. However, due to the way enumeration works, we often have to split our enumerator methods into two so that things like argument validation occur immediately, rather than when the first item in the sequence is requested, like this:

The NumbersImpl method is only ever used by the public-facing Numbers method, but we cannot make that any clearer. However, with C#7 and local functions, we can now embed that method declaration into the Numbers method and make our code explicit.

There are a couple of things to note here. First, we can declare the local function after it has been called; unlike anonymous methods and lambda expressions, local functions are just like any other method; they are part of the program declaration rather than its execution. Second, and somewhat surprisingly2, we can use closures.

Closures in Local Functions

With lambda expressions and anonymous methods, closures are hoisted into member variables of an anonymous type, but this is not how local functions work; local functions do not necessarily get their own anonymous type3. So how do closures work in local functions? Well, the compiler performs a little code-rewriting for us to effectively hoist the closures into method arguments so that we don't have to repeat ourselves.

In Conclusion

Local functions provide a valuable alternative to anonymous methods and lambda expressions, and one-time use member functions. Not only do they make a clear distinction between run-time and compile-time, making the intent clear, but also by co-locating a single-use method with the code that calls it, we can make our code more readable. Of course, as with many other features of high-level languages like C#, this could be abused and make code horribly unreadable, so keep each other honest and be sure to call out incorrect or dubious usage when you see it.

You can read more about local functions in the official documentation.

What do you think? Will you use this new feature of C#? Does it make the language better? Please leave your views in the comments. Next week, we'll take a look at some of the changes C#7 makes to returning values from our methods.


  1. Lambda expressions are a terser syntax for anonymous methods 

  2. at least to me 

  3. Local functions that implement enumerators do get an anonymous type, but that's a special case