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Module OUnit

module OUnit: sig .. end
Unit test building blocks
Author(s): Maas-Maarten Zeeman, Sylvain Le Gall


Assertions are the basic building blocks of unittests.

val assert_failure : string -> 'a
Signals a failure. This will raise an exception with the specified string.
Raises Failure signal a failure
val assert_bool : string -> bool -> unit
Signals a failure when bool is false. The string identifies the failure.
Raises Failure signal a failure
val (@?) : string -> bool -> unit
Shorthand for assert_bool
Raises Failure to signal a failure
val assert_string : string -> unit
Signals a failure when the string is non-empty. The string identifies the failure.
Raises Failure signal a failure
val assert_command : ?exit_code:Unix.process_status ->
?sinput:char Stream.t ->
?foutput:(char Stream.t -> unit) ->
?use_stderr:bool ->
?env:string array -> ?verbose:bool -> string -> string list -> unit
assert_command prg args Run the command provided.
Since 1.1.0
exit_code : expected exit code
sinput : provide this char Stream.t as input of the process
foutput : run this function on output, it can contains an assert_equal to check it
use_stderr : redirect stderr to stdout
env : Unix environment
verbose : if a failure arise, dump stdout/stderr of the process to stderr
val assert_equal : ?cmp:('a -> 'a -> bool) ->
?printer:('a -> string) ->
?pp_diff:(Format.formatter -> 'a * 'a -> unit) ->
?msg:string -> 'a -> 'a -> unit
assert_equal expected real Compares two values, when they are not equal a failure is signaled.
Version: 1.1.0
Raises Failure signal a failure
cmp : customize function to compare, default is =
printer : value printer, don't print value otherwise
pp_diff : if not equal, ask a custom display of the difference using diff fmt exp real where fmt is the formatter to use
msg : custom message to identify the failure
val assert_raises : ?msg:string -> exn -> (unit -> 'a) -> unit
Asserts if the expected exception was raised.
Raises Failure description
msg : identify the failure

Skipping tests

In certain condition test can be written but there is no point running it, because they are not significant (missing OS features for example). In this case this is not a failure nor a success. Following functions allow you to escape test, just as assertion but without the same error status.

A test skipped is counted as success. A test todo is counted as failure.

val skip_if : bool -> string -> unit
skip cond msg If cond is true, skip the test for the reason explain in msg. For example skip_if (Sys.os_type = "Win32") "Test a doesn't run on windows".
Since 1.0.3
val todo : string -> unit
The associated test is still to be done, for the reason given.
Since 1.0.3

Compare Functions

val cmp_float : ?epsilon:float -> float -> float -> bool
Compare floats up to a given relative error.
epsilon : if the difference is smaller epsilon values are equal


A bracket is a functional implementation of the commonly used setUp and tearDown feature in unittests. It can be used like this:

"MyTestCase" >:: (bracket test_set_up test_fun test_tear_down)

val bracket : (unit -> 'a) -> ('a -> unit) -> ('a -> unit) -> unit -> unit
bracket set_up test tear_down The set_up function runs first, then the test function runs and at the end tear_down runs. The tear_down function runs even if the test failed and help to clean the environment.
val bracket_tmpfile : ?prefix:string ->
?suffix:string ->
?mode:Pervasives.open_flag list ->
(string * Pervasives.out_channel -> unit) -> unit -> unit
bracket_tmpfile test The test function takes a temporary filename and matching output channel as arguments. The temporary file is created before the test and removed after the test.
Since 1.1.0
prefix : see Filename.open_temp_file
suffix : see Filename.open_temp_file
mode : see Filename.open_temp_file

Constructing Tests

type test_fun = unit -> unit 
The type of test function

type test =
| TestCase of test_fun
| TestList of test list
| TestLabel of string * test
The type of tests
val (>:) : string -> test -> test
Create a TestLabel for a test
val (>::) : string -> test_fun -> test
Create a TestLabel for a TestCase
val (>:::) : string -> test list -> test
Create a TestLabel for a TestList

Some shorthands which allows easy test construction.


val test_decorate : (test_fun -> test_fun) -> test -> test
test_decorate g tst Apply g to test function contains in tst tree.
Since 1.0.3
val test_filter : ?skip:bool -> string list -> test -> test option
test_filter paths tst Filter test based on their path string representation.
Since 1.0.3

Retrieve Information from Tests

val test_case_count : test -> int
Returns the number of available test cases

type node =
| ListItem of int
| Label of string
Types which represent the path of a test
type path = node list 
The path to the test (in reverse order).
val string_of_node : node -> string
Make a string from a node
val string_of_path : path -> string
Make a string from a path. The path will be reversed before it is tranlated into a string
val test_case_paths : test -> path list
Returns a list with paths of the test

Performing Tests

type test_result =
| RSuccess of path
| RFailure of path * string
| RError of path * string
| RSkip of path * string
| RTodo of path * string
The possible results of a test

type test_event =
| EStart of path
| EEnd of path
| EResult of test_result
Events which occur during a test run
val perform_test : (test_event -> 'a) -> test -> test_result list
Perform the test, allows you to build your own test runner
val run_test_tt : ?verbose:bool -> test -> test_result list
A simple text based test runner. It prints out information during the test.
verbose : print verbose message
val run_test_tt_main : ?arg_specs:(Arg.key * Arg.spec * Arg.doc) list ->
?set_verbose:(bool -> unit) -> test -> test_result list
Main version of the text based test runner. It reads the supplied command line arguments to set the verbose level and limit the number of test to run.
Version: 1.1.0
arg_specs : add extra command line arguments
set_verbose : call a function to set verbosity