I have two gen_servers that communicate using gen_tcp sockets.
The first gen_server exports a function, that when called builds (calling another function) a RFC 791 packet, connects to a socket where the other gen_server is listening for incoming connections, and sends the packet to it.
I tested this in the shell and it is working, but what would be the right tool/way to test such a code? Should I use eunit or or is there any other tool more suitable?
Moreover I would like to know what should I actually test? Only the sending part or also function for packet construction?
You can definitely write some EUnit tests for every gen_servers:
http://www.erlang.org/doc/apps/eunit/chapter.html
http://learnyousomeerlang.com/eunit#the-need-for-tests
You can also have a look at Common Test to test the interaction:
http://www.erlang.org/doc/apps/common_test/basics_chapter.html
http://learnyousomeerlang.com/common-test-for-uncommon-tests#what-is-common-test
Since your implementation strongly depends on the data passed, I would have a look to generators provided by QuickCheck Mini or PropEr:
http://www.quviq.com/
http://proper.softlab.ntua.gr/
A brief explaination on how you can improve your unit tests with something like QuickCheck mini is available here:
http://www.erlang-solutions.com/upload/docs/85/EUG-London-Apr2011.pdf
As a start, I would focus on testing the functions you export (the module interface). You can still add more tests later.
Related
I would like to create a wxPython app such that:
If I run a second instance of that app (e.g., call the Python script from the shell a second time), no new instance should be created.
Instead, the toplevel frame of the already running instance should be raised and focussed.
The first point can be easily implemented by wx.SingleInstanceChecker (see the example code there), but at least the example code only gives a way for making the second instance of the app abort, but not raise the existing app's main frame.
I am using wxPython-Phoenix with Python 3.
Claritication: I would much prefer an out-of-the-box solution like wx.SingleInstanceChecker (that is, not implement my own locking and IPC solution).
You can use any kind of IPC to send a message asking the other program to do whatever needs to be done (just raise its top level window or maybe handle the command line options passed to the second instance). In C++ there are wxConnection and the related wxServer and wxClient classes that can be used for this, but I'm not sure if they're wrapped by wxPython -- however you could use any Python IPC module instead, if they aren't.
As has been pointed out, the "correct" way to do this is IPC because you have a new process that is supposed to affect a change (raise and focus) in another process.
What you seem to want is to take advantage of the IPC channel that wx.SingleInstanceChecker is already using to do your work. Unfortunately, you can't. That class is implemented in the wxWidgets c++ code and therefore there are no Python bindings to the internal workings of the class.
However, you can probably abuse wx.SingleInstanceChecker to do what you want. In your program, you can set up a timer at some rapid interval (say, 250ms) that will constantly check IsAnotherRunning() from your main process. Therefore, when your second process starts up, the first will notice and can raise itself to the front. You would just have to wait for a little bit in the secondary process before it exits, to give the first time to notice.
How could I automate interactions with command line programs that expose a text terminal interface with Perl 6 for testing purposes?
If you want to use Perl 6 to automate execution or testing of console applications, I think you're going to use NativeCall to interact with the expect library. Once expect is installed, man libexpect will show its API documentation, though the way of accessing the documentation (such as the manpage name) may differ per package distribution.
Expect has APIs to launch a program, wait for text to appear on the (emulated) console (to "expect" text), and send text to the console (to emulate typing). The most common use case is to automate programs which require password input. Expect is often scripted--it is an interpreter--but there's no reason not to use it from a higher level programming language.
Edit: I somewhat answered the wrong question. The OP is interested in testing Perl 6 modules with Perl 6. That said, using expect to launch a second Perl 6 interpreter which uses the module is still the strongest, most strict way to test the application. You don't need to know what type of terminal library the module uses, because expect should be compatible with nearly all of them. You can send text to the STDIN pipe of a subprocess, but that's not as strong as the subprocess (console) communication you can get from expect. I don't know if there's a way to hijack whichever terminal library the module uses and communicate with it directly.
If it's just a plain interface, you could just run the program and collect output. The currently-experimental Testo module has is-run routine. You could use that directly, or if experimental status is bothersome, copy the guts of it into your own helper routine.
Take a look at Sparrow6 Task Check Language - Perl6 based DSL to verify text output. I've done a lot terminal apps testing using it.
I am evaluating different multiprocessing libraries for a fault tolerant application. I basically need any process to be allowed to crash without stopping the whole application.
I can do it using the fork() system call. The limit here is that the process can be created on the same machine, only.
Can I do the same with MPI? If a process created with MPI crashes, can the parent process keep running and eventually create a new process?
Is there any alternative (possibly multiplatform and open source) library to get the same result?
As reported here, MPI 4.0 will have support for fault tolerance.
If you want collectives, you're going to have to wait for MPI-3.something (as High Performance Mark and Hristo Illev suggest)
If you can live with point-to-point, and you are a patient person willing to raise a bunch of bug reports against your MPI implementation, you can try the following:
disable the default MPI error handler
carefully check every single return code from your MPI programs
keep track in your application which ranks are up and which are down. Oh, and when they go down they can never get back. but you're unable to use collectives anyway (see my opening statement), so that's not a huge deal, right?
Here's an old paper (back when Bill still worked at Argonne. I think it's from 2003):
http://www.mcs.anl.gov/~lusk/papers/fault-tolerance.pdf . It lays out the kinds of fault tolerant things one can do in MPI. Perhaps such a "constrained MPI" might still work for your needs.
If you're willing to go for something research quality, there's two implementations of a potential fault tolerance chapter for a future version of MPI (MPI-4?). The proposal is called User Level Failure Mitigation. There's an experimental version in MPICH 3.2a2 and a branch of Open MPI that also provides the interfaces. Both are far from production quality, but you're welcome to try them out. Just know that since this isn't in the MPI Standard, the function prefixes are not MPI_*. For MPICH, they're MPIX_*, for the Open MPI branch, they're OMPI_* (though I believe they'll be changing theirs to be MPIX_* soon as well.
As Rob Latham mentioned, there will be lots of work you'll need to do within your app to handle failures, though you don't necessarily have to check all of your return codes. You can/should use MPI error handlers as a callback function to simplify things. There's information/examples in the spec available along with the Open MPI branch.
Currently writing twisted trial tests for an multi-component order flow system that are run together in a single package.
Each test involves calls to external OS proxy objects that are used to regulate traffic - these are common across all tests being run in a package, but across different environments and executions, different ports/ip addresses may be assigned.
Using the test setUp and tearDown methods work, but require constant setting up of connections/port assignments for each test with uncertain wait times for ports to clear.
Is there a way to set up these objects when trial starts up before running the first test, maintain these objects and allow inspection of those object variables, and then allow a teardown on completion of the trial package containing the tests?
You probably don't need to do the set up when trial starts up; rather, you need to do the set up when trial runs the first test that depends on the given fixture. Since trial runs a global reactor, you can use that for your final tear-down before Trial is done.
There's an example of this in the way Calendar Server sets up a Postgres database for testing.
Use testresources:
testresources is attempting to extend unittest with a clean and simple api to provide test optimisation where expensive common resources are needed for test cases
I'm working on a project which will entail multiple devices, each with an embedded (ARM) processor, communicating. One development approach which I have found useful in the past with projects that only entailed a single embedded processor was develop the code using Visual Studio, divided into three portions:
Main application code (in unmanaged C/C++ [see note])
I/O-simulating code (C/C++) that runs under Visual Studio
Embedded I/O code (C), which Visual Studio is instructed not to build, runs on the target system. Previously this code was for the PIC; for most future projects I'm migrating to the ARM.
Feeding the embedded compiler/linker the code from parts 1 and 3 yields a hex file that can run on the target system. Running parts 1 and 2 together yields code which can run on the PC, with the benefit of better debugging tools and more precise control over I/O behavior (e.g. I can make the simulation code introduce certain types of random hiccups more easily than I can induce controlled hiccups on real hardware).
Target code is written in C, but the simulation environment uses C++ so as to simulate I/O registers. For example, I have a PortArray data structure; the header file for the embedded compiler includes a line like unsigned char LATA # 0xF89; and my header file for simulation includes #define LATA _IOBIT(f89,1) which in turn invokes a macro that accesses a suitable property of an I/O object, so a statement like LATA |= 4; will read the simulated latch, "or" the read value with 4, and write the new value. To make this work, the target code has to compile under C++ as well as under C, but this mostly isn't a problem. The biggest annoyance is probably with enum types (which behave as integers in C, but have to be coaxed to do so in C++).
Previously, I've used two approaches to making the simulation interactive:
Compile and link a DLL with target-application and simulation code, and have VB code in the same project which interacts with it.
Compile the target-application code and some simulation code to an EXE with instance of Visual Studio, and use a second instance of Visual Studio for the simulation-UI. Have the two programs communicate via TCP, so nearly all "real" I/O logic is in the simulation program. For example, the aforementioned `LATA |= 4;` would send a "read port 0xF89" command to the TCP port, get the response, process the received value, and send a "write port 0xF89" command with the result.
I've found the latter approach to run a tiny bit slower than the former in some cases, but it seems much more convenient for debugging, since I can suspend execution of the unmanaged simulation code while the simulation UI remains responsive. Indeed, for simulating a single target device at a time, I think the latter approach works extremely well. My question is how I should best go about simulating a plurality of target devices (e.g. 16 of them).
The difficulty I have is figuring out how to make each simulated instance get its own set of global variables. If I were to compile to an EXE and run one instance of the EXE for each simulated target device, that would work, but I don't know any practical way to maintain debugger support while doing that. Another approach would be to arrange the target code so that everything would compile as one module joined together via #include. For simulation purposes, everything could then be wrapped into a single C++ class, with global variables turning into class-instance variables. That would be a bit more object-oriented, but I really don't like the idea of forcing all the application code to live in one compiled and linked module.
What would perhaps be ideal would be if the code could load multiple instances of the DLL, each with its own set of global variables. I have no idea how to do that, however, nor do I know how to make things interact with the debugger. I don't think it's really necessary that all simulated target devices actually execute code simultaneously; it would be perfectly acceptable for simulation instances to use cooperative multitasking. If there were some way of finding out what range of memory holds the global variables, it might be possible to have the 'task-switch' method swap out all of the global variables used by the previously-running instance and swap in the contents applicable to the instance being switched in. Although I'd know how to do that in an embedded context, though, I'd have no idea how to do that on the PC.
Edit
My questions would be:
Is there any nicer way to allow simulation logic to be paused and examined in VS2010 debugger, while keeping a responsive UI for the simulator front-end, than running the simulator front end and the simulator logic in separate instances of VS2010, if the simulation logic must be written in C and the simulation front end in managed code? For example, is there a way to tell the debugger that when a breakpoint is hit, some or all other threads should be allowed to keep running while the thread that had hit the breakpoint sits paused?
If the bulk of the simulation logic must be source-code compatible with an embedded system written in C (so that the same source files can be compiled and run for simulation purposes under VS2010, and then compiled by the embedded-systems compiler for use in real hardware), is there any way to have the VS2010 debugger interact with multiple simulated instances of the embedded device? Assume performance is not likely to be an issue, but the number of instances will be large enough that creating a separate project for each instance would be likely be annoying in the absence of any way to automate the process. I can think of three somewhat-workable approaches, but don't know how to make any of them work really nicely. There's also an approach which would be better if it's possible, but I don't know how to make it work.
Wrap all the simulation code within a single C++ class, such that what would be global variables in the target system become class members. I'm leaning toward this approach, but it would seem to require everything to be compiled as a single module, which would annoyingly affect the design of the target system code. Is there any nice way to have code access class instance members as though they were globals, without requiring all functions using such instances to be members of the same module?
Compile a separate DLL for each simulated instance (so that e.g. if I want to run up to 16 instances, I would include 16 DLL's in the project, all sharing the same source files). This could work, but every change to the project configuration would have to be repeated 16 times. Really ugly.
Compile the simulation logic to an EXE, and run an appropriate number of instances of that EXE. This could work, but I don't know of any convenient way to do things like set a breakpoint common to all instances. Is it possible to have multiple running instances of an EXE attached to a single debugger instance?
Load multiple instances of a DLL in such a way that each instance gets its own global variables, while still being accessible in the debugger. This would be nicest if it were possible, but I don't know any way to do so. Is it possible? How? I've never used AppDomains, but my intuition would suggest that might be useful here.
If I use one VS2010 instance for the front-end, and another for the simulation logic, is there any way to arrange things so that starting code in one will automatically launch the code in the other?
I'm not particularly committed to any single simulation approach; while it might be nice to know if there's some way of slightly improving the above, I'd also like to know of any other alternative approaches that could work even better.
I would think that you'd still have to run 16 copies of your main application code, but that your TCP-based I/O simulator could keep a different set of registers/state for each TCP connection that comes in.
Instead of a bunch of global variables, put them into a single structure that encompasses the I/O state of a single device. Either spawn off a new thread for each socket, or just keep a list of active sockets and dedicate a single instance of the state structure for each socket.
the simulators I have seen that handle multiple instances of the instruction set/processor are designed that way. There is a structure usually that contains a complete set of registers, and a new pointer or an array of these structures are used to multiply them into multiple instances of the processor.