ESpec

ESpec is a BDD testing framework for Elixir.

It is NOT a wrapper around ExUnit but a completely new testing framework written from scratch.

ESpec is inspired by RSpec and the main idea is to be close to its perfect DSL.

Features

• Test organization with describe, context, it, and etc blocks.
• Familiar matchers: eq, be_close_to, raise_exception, etc.
• Possibility to add custom matchers.
• There are three (!) types of expectation syntax:
  • RSpec syntax with expect helper: expect(smth1).to eq(smth2) or is_expected.to eq(smth) when subject is defined;
  • expect syntax with pipe operator expect smth1 |> to(eq smth2) or is_expected |> to(eq smth) when subject is defined;
  • should syntax: smth1 |> should(eq smth2) or should eq smth when subject is defined.
• before and finally blocks (like RSpec before and after).
• let, let! and subject.
• Shared examples.
• Async examples.
• Mocks with Meck.
• Doc specs.
• HTML and JSON outputs.
• Etc and etc.

Contents

• Installation
• Run specs
• Context blocks
• Examples
• Filters
• ‘before’ and ‘finally’
• ‘shared’ data
• ‘let’ and ‘subject’
• Shared examples
• Async examples
• Matchers
• Custom matchers
• described_module
• Mocks
• Doc specs
• Configuration and options
• Contributing

Installation

Add espec to dependencies in the mix.exs file:

def deps do
  ...
  {:espec, "~> 0.8.20", only: :test},
  #{:espec, github: "antonmi/espec", only: :test}, to get the latest version
  ...
end

mix deps.get

Then run:

MIX_ENV=test mix espec.init

The task creates spec/spec_helper.exs and spec/example_spec.exs.

Set preferred_cli_env for espec in the mix.exs file:

def project do
  ...
  preferred_cli_env: [espec: :test],
  ...
end

Or run with MIX_ENV=test:

MIX_ENV=test mix espec

Place your _spec.exs files into spec folder. use ESpec in the ‘spec module’.

defmodule SomeSpec do
  use ESpec
  it do: expect true |> to(be_true)
  it do: expect(1+1).to eq(2)
  it do: (1..3) |> should(have 2)
end

Run specs

mix espec

Run specific spec:

mix espec spec/some_spec.exs:25

Read the help:

MIX_ENV=test mix help espec

Context blocks

There are three macros with the same functionality: context, describe, and example_group.

Context can have description and options.

defmodule SomeSpec do
  use ESpec

  example_group do
    context "Some context" do
      it do: expect "abc" |> to(match ~r/b/)
    end

    describe "Some another context with opts", focus: true do
      it do: 5 |> should(be_between 4, 6)
    end
  end
end

Available options are:

• skip: true or skip: "Reason" - skips examples in the context;
• focus: true - sets focus to run with --focus option.

There are also xcontext, xdescribe, xexample_group macros to skip example groups. And fcontext, fdescribe, fexample_group for focused groups.

‘spec’ module is also a context with module name as description. One can add options for this context after use ESpec:

defmodule SomeSpec do
  use ESpec, skip: "Skip all examples in the module"
  ...
end

Examples

example, it, and specify macros define the ‘spec example’.

defmodule SomeSpec do

  example do: expect [1,2,3] |> to(have_max 3)

  it "Test with description" do
    4.2 |> should(be_close_to 4, 0.5)
  end

  specify "Test with options", [pending: true], do: "pending"
end

You can use skip, pending or focus options to control evaluation. There are also macros:

• xit, xexample, xspecify - to skip;
• fit, fexample, fspecify, focus - to focus;
• pending/1, example/1, it/1, specify/1 - for pending examples.

  defmodule SomeSpec do
  use ESpec
  
  xit "skip", do: "skipped"
  focus "Focused", do: "Focused example"
  
  it "pending example"
  pending "it is also pending example"
  end

##Filters The are --only, --exclude and --string command line options.

One can tag example or context and then use --only or --exclude option to run (or exclude) tests with specific tag.

defmodule SomeSpec do
  use ESpec

  context "context with tag", context_tag: :some_tag do
    it do: "some example"
    it "example with tag", example_tag: true do
     "another example"
    end
  end
end

mix espec spec/some_spec.exs --only context_tag:some_tag --exclude example_tag

This runs only one test “some example”

You can also filter examples by --string option which filter examples which contain given string it their nested description.

mix espec spec/some_spec.exs --string 'context with tag'

before and finally

before blocks are evaluated before the example and finally runs after the example.

The blocks can return {:shared, key: value, ...} or (like in ExUnit) {:ok, key: value, ...}, so the keyword list will be saved in the dictionary and can be accessed in other before blocks, in the example, and in finally blocks through ‘shared`: elixir defmodule SomeSpec do use ESpec before do: {:shared, a: 1} context "Context" do before do: {:shared, b: shared[:a] + 1} finally do: "#{shared[:b]} == 2" it do: shared.a |> should(eq 1) it do: shared.b |> should(eq 2) finally do: "This finally will not be run. Define 'finally' before the example" end end Note, that finally blocks must be defined before the example. You can configure ‘global’ before and finally in spec_helper.exs: elixir ESpec.start ESpec.configure fn(config) -> config.before fn -> {:shared, answer: 42} end #can assign values in dictionary config.finally fn(shared) -> shared.answer end #can access assigns end These functions will be called before and after each example which ESpec runs. ## ‘shared’ data shared is used to share data between spec blocks. You can access data by shared.some_key or shared[:some_key]. shared.some_key will raise exception if the key ‘somekey’ does not exist, while shared[:some_key] will return nil. The shared variable appears in your before, finally, in config.before and config.finally, in let and example blocks. before and finally blocks (including ‘global’) can modify the dictionay when return {:shared, key: value}. The example bellow illustrate the life-cycle of shared: spec_helper.exselixir ESpec.start ESpec.configure fn(config) -> config.before fn -> {:shared, answer: 42} end # shared == %{anwser: 42} config.finally fn(shared) -> IO.puts shared.answer end # it will print 46 endsome_spec.exs: elixir defmodule SomeSpec do use ESpec before do: {:shared, answer: shared.answer + 1} # shared == %{anwser: 43} finally do: {:shared, answer: shared.answer + 1} # shared == %{anwser: 46} context do before do: {:shared, answer: shared.answer + 1} # shared == %{anwser: 44} finally do: {:shared, answer: shared.answer + 1} # shared == %{anwser: 45} it do: shared.answer |> should(eq 44) end end So, ‘config.finally’ will print 46. Pay attention to how finally blocks are defined and evaluated. ## let and subjectlet and let! have the same behaviour as in RSpec. Both defines memoizable functions in ‘spec module’. The value will be cached across multiple calls in the same example but not across examples. let is not evaluated until the first time the function it defines is invoked. Use let! to force the invocation before each example. The shared is available in ‘lets’ but neither let nor let! can modify the dictionary. elixir defmodule SomeSpec do use ESpec before do: {:shared, a: 1} let! :a, do: shared.a let :b, do: shared.a + 1 it do: expect a |> to(eq 1) it do: expect b |> to(eq 2) endsubject and subject! are just aliases for let :subject, do: smth and let! :subject, do: smth. You can use is_expected macro (or a simple should expression) when subject is defined. elixir defmodule SomeSpec do use ESpec subject(1+1) it do: is_expected |> to(eq 2) it do: should eq 2 context "with block" do subject do: 2+2 it do: is_expected |> to_not(eq 2) it do: should_not eq 2 end end ## Shared Examples One can reuse the examples defined in spec module. elixir defmodule SharedSpec do use ESpec, shared: true subject shared.hello it do: should eq("world!") endshared: true marks examples in the module as shared, so the examples will be skipped until you reuse them. You can use the examples with it_behaves_like or its alias include_examples macro: elixir defmodule UseSharedSpec do use ESpec before do: {:ok, hello: "world!"} it_behaves_like(SharedSpec) #or include_examples(SharedSpec) end Be carefull with let and let! when using shared examples. You can’t access let from ‘spec module’ in ‘shared module’. elixir defmodule SomeSharedSpec do use ESpec, shared: true it do: expect a |> to(eq "a") end defmodule SomeSpec do use ESpec let :a, do: "a" include_examples(SomeSharedSpec) end Elixir will not compile SomeSharedSpec module with error: function a/0 undefined. So use shared dictionary in ‘before’ block to set the value. ## Async examples There is an async: true option you can set for the context or for the individual example: elixir defmodule AsyncSpec do use ESpec, async: true it do: "async example" context "Sync", async: false do it do: "sync example" it "async again", async: true do "async" end end end The examples will be partitioned into two queries. Examples in asynchronous query will be executed in parallel in different processes. Don’t use async: true if you change the global state in your specs! ## Matchers #### Equality elixir expect actual |> to(eq expected) # passes if actual == expected expect actual |> to(eql expected) # passes if actual === expected expect actual |> to(be_close_to expected, delta) expect actual |> to(be_between hard_place, rock) #### Comparisons Can be used with :>, :<, :>=, :<=, and etc. elixir expect actual |> to(be operator, value) Passes if apply(Kernel, operator, [actual, value]) == true #### Booleans elixir expect actual |> to(be_true) expect actual |> to(be_truthy) expect actual |> to(be_false) expect actual |> to(be_falsy) #### Regular expressions elixir expect actual |> to(match ~r/expression/) expect actual |> to(match "string") #### Enumerable There are many helpers to test enumerable collections: elixir expect collection |> to(be_empty) #Enum.count(collection) == 0 ... have value #Enum.member?(collection, value) ... have_all func #Enum.all?(collection, func) ... have_any func #Enum.any?(collection, func) ... have_at position, value #Enum.at?(collection, position) == value ... have_count value #Enum.count(collection) == value ... have_size value #alias ... have_length value #alias ... have_count_by func, value #Enum.count(collection, func) == value ... have_max value #Enum.max(collection) == value ... have_max_by func, value #Enum.max_by(collection, fun) == value ... have_min value #Enum.min(collection) == value ... have_min_by func, value #Enum.min_by(collection, fun) == value #### List elixir expect list |> to(have_first value) #List.first(list) == value ... have_last value #List.last(list) == value ... have_hd value #hd(list) == value ... have_tl value #tl(list) == value #### String elixir expect string |> to(have_first value) #String.first(string) == value ... have_last value #String.last(string) == value ... start_with value #String.starts_with?(string, value) ... end_with value #String.end_with?(string, value) ... have value #String.contains?(string, value) ... have_at pos, value #String.at(string, pos) == value ... have_length value #Stirng.length(string) == value ... have_size value #alias ... have_count value #alias ... be_valid_string #String.valid?(string) ... be_printable #String.printable?(string) #### Dict elixir expect dict |> to(have_key value) #Dict.has_key?(value) expect dict |> to(have_value value) #Enum.member?(Dict.values(dict), value) #### Type checking elixir expect :espec |> to(be_atom) #is_atom(:espec) == true ... be_binary ... be_bitstring ... be_boolean ... ... ... ... ... be_tuple ... be_function ... be_function arity ... be_struct ... be_struct StructExample #### Exceptions elixir expect function |> to(raise_exception) expect function |> to(raise_exception ErrorModule) expect function |> to(raise_exception ErrorModule, "message") #### Throws elixir expect function |> to(throw_term) expect function |> to(throw_term term) #### Change state Test if call of function1 change the function2 returned value to smth or from to smth elixir expect function1 |> to(change function2, to) expect function1 |> to(change function2, from, to) #### Check result Test if function returns {:ok, result} or {:error, reason} tuple elixir expect {:ok, :the_result} |> to(be_ok_result) expect {:error, :an_error} |> to(be_error_result) ## Custom matchers You can define your own matchers! The only functions you should implement is match/2, success_message/4, and error_message. Read the wiki page for detailed instructions. There is an example in custom_assertion_spec.exs. ## described_module If you keep the naming convention ‘module TheModuleSpec is spec for TheModule’ you can access tested module by described_module helper. elixir defmodule TheModule do def fun, do: :fun end defmodule TheModuleSpec do use ESpec it do: expect described_module.fun |> to(eq :fun) end ## Mocks ESpec uses Meck to mock functions. You can mock the module with ‘allow accept’: elixir defmodule SomeSpec do use ESpec context "with old syntax" before do: allow(SomeModule).to accept(:func, fn(a,b) -> a+b end) it do: expect SomeModule.func(1, 2) |> to(eq 3) end context "with new syntax" before do: allow SomeModule |> to(accept :func, fn(a,b) -> a+b end) it do: expect SomeModule.func(1, 2) |> to(eq 3) end end If you don’t specify the function to return ESpec creates stubs with arity 0 and 1: fn -> end and `fn() -> end, which returnnil. ```elixir defmodule SomeSpec do use ESpec before do: allow SomeModule |> to(accept :func) it do: expect SomeModule.func |> to(be_nil) it do: expect SomeModule.func(42) |> to(be_nil) end ``` Behind the scenes 'allow accept' makes the following: ```elixir :meck.new(module, [:non_strict, :passthrough]) :meck.expect(module, name, function) ``` Find the explanation aboute the:nonstrictand:passthroughoptions [here](https://github.com/eproxus/meck/blob/master/src/meck.erl). The default options ([:non_strict, :passthrough]) can be overridden: ```elixir allow SomeModule) |> to(accept :func, fn(a,b) -> a+b end, [:non_strict, :unstick]) ``` All the mocked modules are unloaded whith:meck.unload(modules)after each example. You can also pass a list of atom-function pairs to theacceptfunction: ```elixir allow SomeModule |> to(accept f1: fn -> :f1 end, f2: fn -> :f2 end) ``` One can usepassthrough/1` function to call the original function: ```elixir before do allow SomeModule |> to(accept(:fun, fn :mocked -> “mock!” -> passthrough([args]) end)) end it do: expect SomeModule.fun(:mocked) |> to(eq “mock!”) it do: expect SomeModule.fun(2) |> to(eq 3) The `passthrough/1` just calls the `:meck.passthrough/1` from the `:meck` module. There is also an expectation to check if the module accepted a function call:elixir accepted(func, args \ :any, opts \ [pid: :any, count: :any]) So, the options are: - test if the function is called with some particular arguments of with `any`; - specify the `pid` of the process which called the function; - test the count of function calls.elixir defmodule SomeSpec do use ESpec before do allow SomeModule |> to(accept :func, fn(a,b) -> a+b end) SomeModule.func(1, 2) end
it do: expect SomeModule |> to(accepted :func) it do: expect SomeModule |> to(accepted :func, [1,2]) describe “with options” do defmodule Server do def call(a, b) do ESpec.SomeModule.func(a, b) ESpec.SomeModule.func(a, b) end end before do pid = spawn(Server, :call, [1, 2]) :timer.sleep(100) {:ok, pid: pid} end it do: expect ESpec.SomeModule |> to(accepted :func, [1,2], pid: shared.pid, count: 2) end end `accepted` assertion checks `:meck.history(SomeModule)`. See [meck](https://github.com/eproxus/meck) documentation. Don't use `async: true` when using mocks! ## Doc specs ESpec has functionality similar to [`ExUnit.DocTest`](http://elixir-lang.org/docs/stable/ex_unit/). Read more about docs syntax [here](http://elixir-lang.org/docs/stable/ex_unit/) The functionality is implemented by two modules: `ESpec.DocExample` parses module documentation and `ESpec.DocTest` creates 'spec' examples for it. `ESpec.DocExample` functions is just copy-paste of `ExUnit.Doctest` parsing functionality. `ESpec.DocTest` implement `doctest` macro which identical to `ExUnit` analogue.elixir defmodule SomeSpec do use ESpec doctest MySuperModule end
There are three options (similar to `ExUnit.DocTest`): `:except` - generate specs for all functions except those listed (list of {function, arity} tuples).elixir defmodule SomeSpec do use ESpec doctest MySuperModule, except: [fun: 1, func: 2] end
`:only` — generate specs only for functions listed (list of {function, arity} tuples). And `:import` to test a function defined in the module without referring to the module name.Default is `false`. Use this option with care because you can clash with another modules. There are three types of specs can be generated based on docs. - Examples where input and output can be evaluated. For example:elixir @doc “”” iex> Enum.map [1, 2, 3], fn(x) -> …> x 2 …> end [2,4,6] “”” Such examples will be converted to:elixir it “Example description” do expect input |> to(eq output) end
- Examples which return complex structure so Elixir prints it as `#Name<...>.`:elixir @doc “”” iex> Enum.into([a: 10, b: 20], HashDict.new) #HashDict<[b: 20, a: 10]> “”” The examples will be converted to:elixir it “Example description” do expect inspect(input) |> to(eq output) end - Examples with exceptions:elixir @doc “”” iex(1)> String.to_atom((fn() -> 1 end).()) ** (ArgumentError) argument error “”” The examples will be tested as:elixir it “Example description” do expect fn -> input end |> to(raise_exception error_module, error_message) end ## Configuration and optionssh MIX_ENV=test mix help espec#### Spec paths and pattern You can change (in `mix.exs` file) the folder where your specs are and the pattern to match the files.elixir def project do … spec_paths: [“my_specs”, “espec”], spec_pattern: “_espec.exs”, … end #### Coverage One can run specs with coverage:sh mix espec –cover Find the results in `/cover` folder. ESpec, like ExUnit, uses very simple wrapper around OTP's cover. But you can override this. Take a look to [coverex](https://github.com/alfert/coverex) as a perfect example. #### Output formats There are three formatters in ESpec: 'doc', 'json' and 'html'. Example:sh mix espec –format=doc The 'doc' format will print detailed description of example and its context. `--trace` option is an alias for `--format=doc`.sh mix espec –trace 'html' and 'json' formatters prepare pretty HTML and JSON outputs. You may use `--format` with `--out` option to write output to the file.sh mix espec –format=html –out=spec.html ## Contributing ##### Contributions are welcome and appreciated! Request a new feature by creating an issue. Create a pull request with new features and fixes. ESpec is tested using ExUnit and ESpec. So run:sh mix test mix espec ```