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Ospecl is a library for writing executable specifications for your OCaml code à la rspec.

Ospecl allows you to build specs, which are nested data structures combining textual descriptions of the component's behaviour, together with the code that can verify it. Specs may then be executed to verify your component's continued conformance.

Specs are built using calls to describe to provide context for a group of executable examples, each constructed through it calls. Examples contain a single expectation which uses matchers to test whether a given value meets some criteria.


let component_spec = 
  describe "some component" [
    it "has some behaviour" begin
      expect my_component (has some_behaviour)
    describe "in some particular context" begin
      let different = in_context my_component in
        it "has some different behaviour" begin
          expect different (has different_behaviour)
        it "does something else too" begin
          different =~ (does something_else)

Here, describe takes a string, which, well, describes what you're specifying, and a list of child specs. it takes a string, which describes the behaviour that this example verifies, and an expectation. expect takes a value and a matcher for that value and returns an expectation, which will be checked when the spec is executed. =~ is an alias for expect which can be used infix.

As you can see, specs may be nested arbitrarily within each other, so you can organise your contexts and examples as you see fit.

A working example can be found in the examples directory, and another one here.


$ make install

will install ospecl as a findlib package and make links to ospecl, ospecl_client and ospecl_server in your $HOME/bin directory.

$ make uninstall

will reverse this.


Matchers are used to construct expectations. They are based on the idea of matchers in hamcrest, which is like a predicate coupled with a way of describing successful and unsucessful matches. Matchers are nice because they are both descriptive on their own, and may be composed to build arbitrary new self-describing constraints on values. Ospecl comes with a core set of matchers in Ospecl.Matchers, but you can define additional matchers on top of Ospecl.Matcher to fit your domain.


There are several ways to execute specs.

Command line


$ ospecl -I dir_with_cmo_files 

ospecl accepts a list of ocaml script files, each of which must define a single value called specs of type Ospecl.Spec.t list. The specs from each of these files will be executed in order and the results reported together.


You can start ospecl_server s and have ospecl_client s connect to them with any number of parallel connections. An ospecl server will respond to each connection by forking off a new process which receives spec file names, executes the specs defined in them, and sends the execution events back to the client. You may thus request a client to open several connections to the same server, or connect it to several different servers and the client will distribute the specs across these connections.

The servers need not be on the same machine as the client but as yet no provision is made for sending the spec files themselves or the modules they reference from the client to the server, so at present they must share a filesystem in order for the server to be able to discover the spec files. The servers can be started with a list of directories to search for the referenced modules.


$ ospecl_server -I src/ -port 7000 &
$ ospecl_client -j 4 -address spec/*.ml

or if the client is started in a different directory from the server

$ find `pwd`/spec/*.ml | xargs ospecl_client -j 4 -address

Runner function

Specs may be executed from your own code by calling the Ospecl.Spec.Exec.execute function, which takes a list of handler s and a list of specs and executes each spec, passing the appropriate execution events to the handlers as they occur. Two sets of handlers are currently provided: Ospecl.Console.progress and Ospecl.Console.documentation. The meaning of these handlers roughly corresponds to the 'progress' and 'documentation' formats in rspec.

You may also define your own handlers to handle execution events in whatever way you wish. The execution events are defined in the Ospecl.Spec.Exec module.


Simple library for specifying and testing OCaml, inspired by rspec and FsUnit.




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