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A lightweight, convention over configuration test framework for Erlang
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etest is a lightweight, convention-over-configuration test framework for Erlang.

It comes with a companion library for testing http / web apps and APIs which is called etest_http

  • etest expects an Erlang application / rebar3-compatible directory structure with the following top level directories: src, and test.

  • Test module file names end with _test.erl ending and test case function names should start with test_.

  • Each test file can implement some or all of the following callbacks:

    • before_suite - Invoked once before all cases,
    • before_test - Invoked before each case,
    • after_test - Invoked after each case,
    • after_suite - Invoked once after all cases, independent of case failure,
  • There are no test generators like in EUnit. If an assertion in a test case fails, the rest of the case will be skipped and etest continues executing the remaining cases.

Example Test Case


% Include etest's assertion macros.

before_suite() ->

before_test() ->

test_application_has_one_user() ->
    ?assert_equal(1, length( myapp_users:all() )).

test_creating_a_new_user() ->
    Old = myapp_users:first(),
    New = myapp_users:create(
        [{name, "Peter"}, {favorite_test_framework, "etest"}]),

    ?assert_equal(2, length( myapp_users:all() )),
    ?assert_not_equal(Old, New),
    ?assert_equal(New, myapp_users:last()).

after_test() ->

after_suite() ->

Available Assertions

Positive Assertions

  • ?assert(Expression)
  • ?assert_equal(Expected, Actual)
  • ?assert_match(Expected, Actual)
  • ?assert_exception(Class, Pattern, Expression)
  • ?assert_error(Pattern, Expression)
  • ?assert_exit(Pattern, Expression)
  • ?assert_throw(Pattern, Expression)

Negated Assertions

This is the same list as in the previous section, with _not or _no inserted in the name.

  • ?assert_not(Expression)
  • ?assert_not_equal(Unexpected, Actual)
  • ?assert_no_match(Unexpected, Actual)
  • ?assert_no_exception(Class, Pattern, Expression)
  • ?assert_no_error(Pattern, Expression)
  • ?assert_no_exit(Pattern, Expression)
  • ?assert_no_throw(Pattern, Expression)


etest has no concept of fixtures like EUnit. If you need some data over and over inside of your tests, you can define macros or functions instead and call them from within your tests.

Focus Tests

From time to time you might want to run a single test case out of your suite to quickly pin down where the underlying program fails. Thus we introduced the concept of Focus Tests, where you would mark one or more test cases with the prefix focus_, then upon running your tests only the marked cases will be executed.



% Include etest's assertion macros.

% This case will be ignored.
test_bar() ->
    % ...
    ?assert_equal(false, true).

% This case will be run.
focus_test_foo() ->
    % ...


There is a quick screencast on vimeo that shows how to use etest in your project:


To install etest add it as a dependency to your rebar.config and also add the test directory to the src_dirs option. This will compile the tests whenever rebar compile is executed and you don't have to compile the tests manually.

Example rebar.config

% Compiler Options for rebar
{erl_opts, [
    {src_dirs, ["src", "test"]}

% Dependencies
{deps, [
    {etest, "1.2.0"}

After updating your rebar.config, run rebar3 get-deps to install etest.

Running the Tests

Before running the tests, they need to be compiled by running rebar3 compile. You can write a simple shell script that compiles everything before running the tests to make your life easier.

Etest comes with a test runner, which by default, is buried in the _build directory _build/default/lib/etest/bin/etest-runner

For convenience you can either symlink it to a top level direcory or create a make task

Run All The Tests

# If you have symlinked it to your app root directory

# If you want to run it from the _build dir

Run a Single Test

etest-runner test/integration/user_login_test.erl

Test Coverage Report

If you want to know how much of your codebase is covered by etest tests, you can set two additional enironment variables (ETEST_BUILD_DIR and WITH_COVERAGE. This will create a coverage directory in you app root directory in which you will find the html reports.

Run the tests like this where ETEST_BUILD_DIR is the build dir of your app so etest knows which modules to cover and with WITH_COVERAGE=true to tell it to generate the report.

rebar3 compile && \
	ETEST_ARGS="-config config/test.config" \
	ETEST_BUILD_DIR="_build/default/lib/[YOUR_APP_NAME]" \

This will run the tests, save the report html files in ./coverage and create some ascii output like this

| Coverage Report                                          |
| Module                                         | Percent |
| myapp_app                                      |  100.00 |
| myapp_config                                   |   91.67 |
| myapp_default_handler                          |   84.21 |
| myapp_session                                  |   85.19 |
| myapp_session_handler                          |   90.32 |
| myapp_session_middleware                       |   54.55 |
| myapp_session_store                            |   69.05 |
| myapp_sql                                      |   75.00 |
| myapp_sql_worker                               |   70.59 |
| myapp_sup                                      |  100.00 |
| myapp_user                                     |   80.00 |
| myapp_users_handler                            |  100.00 |
| myapp_utils                                    |   87.50 |
| myapp_view                                     |   96.15 |

  Failed: 0.  Success: 25.  Total: 25.

Passing Arguments to erl

To pass additional arguments to the erl command you can use the environment variable ETEST_ARGS. For example:

ETEST_ARGS="-config config/test.config" deps/etest/bin/etest-runner

Makefile Example

For absolute convenience here is an example Makefile task which will run all tests with coverage report for the myapp app

	rebar3 compile && ETEST_ARGS="-config config/test.config" WITH_COVERAGE=yes ETEST_BUILD_DIR="_build/default/lib/myapp" _build/default/lib/etest/bin/etest-runner
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