EUnit examples: a test list

While you could specify each test with a single function, you can also use a test “instantiator” (or generator) and have it return a list.

list_of_test_() ->
    [
        fun something/0,
        fun() -> ?assert(true) end,
        ?_assert(true),
        {"description of test", ?_assert(true)},
        {<<"another test">>, fun another_thing/0}
    ].

something() -> ?assert(true).
another_thing() -> ?assert(true).

Note that this is a test generator/instantiator, rather than a simple test. This is denoted by the underscore in the function name: ...test_(). This is required, and EUnit won’t always tell you if you forget.

This example also shows a few of the different ways that you can specify a test:

• As a local function reference – fun something/0.
• As an anonymous function – fun() -> ?assert(true) end.
• Using one of the test-generator macros (the ones starting with an underscore) – ?_assert(true).
• Using a description. This must be a string or a binary.

Note that using anonymous functions results in tests which are, well, anonymous.

This sometimes makes it hard to figure out which test has failed. For example:

  2) list_of_test:-list_of_test_/0-fun-4-/0:8
     Failure/Error: ?assert(false)
       expected: true
            got: false

To get around this, consider using the variants that use named functions: fun something/0, or the descriptions.